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AISIS240 15 (1stprinting)

This document establishes requirements for the design and construction of cold-formed steel structural framing. It integrates previous AISI standards related to floor, wall and roof framing, headers, lateral design, and trusses. The document provides definitions, material specifications, design provisions, and references testing standards.

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Roberto Pérez León

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0% found this document useful (0 votes)

204 views204 pages

AISIS240 15 (1stprinting)

Uploaded by

Roberto Pérez León

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AISI S240-15

AISI STANDARD
North American Standard
for Cold-Formed Steel
Structural Framing

2015 Edition

AISI S240-15

AISI STANDARD
North American Standard
for Cold-Formed Steel
Structural Framing

2015 Edition

AISI S240-15

DISCLAIMER
The material contained herein has been developed by the American Iron and Steel Institute
(AISI) Committee on Framing Standards. The Committee has made a diligent effort to present
accurate, reliable, and useful information on cold-formed steel framing design and installation.
The Committee acknowledges and is grateful for the contributions of the numerous researchers,
engineers, and others who have contributed to the body of knowledge on the subject. Specific
references are included in the Commentary.
With anticipated improvements in understanding of the behavior of cold-formed steel
framing and the continuing development of new technology, this material will become dated. It
is anticipated that AISI will publish updates of this material as new information becomes
available, but this cannot be guaranteed.
The materials set forth herein are for general purposes only. They are not a substitute for
competent professional advice. Application of this information to a specific project should be
reviewed by a design professional. Indeed, in many jurisdictions, such review is required by
law. Anyone making use of the information set forth herein does so at their own risk and
assumes any and all liability arising therefrom.

1st Printing December 2015

This document is copyrighted by AISI. Any redistribution is prohibited.

iii

AISI S240-15

This first edition of AISI S240, North American Standard for Cold-Formed Steel Structural Framing,
is dedicated to John P. Matsen, P.E. John was a widely respected structural engineer for over
three decades and founder and principal of Matsen Ford Design Associates. Throughout his
career, he helped pioneer and expand the use of cold-formed steel framing in structural and
nonstructural applications.
From the inception of the AISI Committee on Framing Standards in 1998, John was an active
member. He served as chair of its High Wind Subcommittee from 1998 to 2001, enabling the
AISI Standard for Cold-Formed Steel FramingPrescriptive Method for One- and Two-Family
Dwellings to be expanded in scope to address high wind areas. He actively engaged in the
Committees numerous subcommittees and task groups, and was always an effective
contributor.
John was also an active member of the Cold-Formed Steel Engineers Institute, helping to author
and review technical notes, providing webinars, serving as a member of the Executive
Committee, and leading as Chair of the Institute from 2009 to 2010. John was always willing to
offer his expertise to help advance the profession.
The cold-formed steel industry gratefully acknowledges his many enduring contributions.

This document is copyrighted by AISI. Any redistribution is prohibited.

AISI S240-15

This Page is Intentionally Left Blank.

This document is copyrighted by AISI. Any redistribution is prohibited.

North American Standard For Cold-Formed Steel Structural Framing, 2015 Edition

PREFACE
The American Iron and Steel Institute (AISI) Committee on Framing Standards has
developed AISI S240, North American Standard for Cold-Formed Steel Structural Framing, to
address requirements for construction with cold-formed steel structural framing that are
common to prescriptive and engineered design. This Standard is intended for adoption and use
in the United States, Canada and Mexico.
This Standard integrated the following AISI Standards into one document:
AISI S200-12, North American Standard for Cold-Formed Steel Framing-General Provisions
AISI S210-07 (2012), North American Standard for Cold-Formed Steel FramingFloor and Roof
System Design (Reaffirmed 2012)
AISI S211-07(2012), North American Standard for Cold-Formed Steel FramingWall Stud
Design (Reaffirmed 2012)
AISI S212-07(2012), North American Standard for Cold-Formed Steel FramingHeader Design
(Reaffirmed 2012)
AISI S213-07w/S1-09(2012), North American Standard for Cold-Formed Steel Framing
Lateral Design with Supplement 1 (Reaffirmed 2012)
AISI S214-12, North American Standard for Cold-Formed Steel FramingTruss Design
Consequently, AISI S240 will supersede all previous editions of the above-mentioned
individual AISI Standards.
In 2015, AISI S400, North American Standard for Seismic Design of Cold-Formed Steel Structural
Systems, was developed. Modifications were made to align the provisions of AISI S240 with
AISI S400, as follows:
The applicability of AISI S240 for seismic design was limited to applications when
specific seismic detailing is not required.
Definitions no longer needed in AISI S240 were removed and remaining definitions
were revised, if needed, for consistency with AISI S400.
Seismic-specific tables for nominal shear strength [resistance] were deleted.
Seismic-specific safety factors and resistance factors were deleted.
Other seismic-specific requirements were removed, as appropriate, and remaining
requirements were generalized for applicability to wind, seismic or other lateral loads.
Also in this edition, a new Chapter F on testing was added to allow reference to applicable
AISI 900-series test Standards. Methods for truss tests, formerly in Section E7, were moved to
Appendix 2.
While not necessary, use of the more stringent requirements for structural members that are
in this Standard for nonstructural members should be permitted, since these should demonstrate
equivalent performance for the intended use to those specified in AISI S220, North American
Standard for Cold-Formed Steel FramingNonstructural Members.
The Committee acknowledges and is grateful for the contributions of the numerous
engineers, researchers, producers and others who have contributed to the body of knowledge
on the subjects. The Committee wishes to also express its appreciation for the support of the
Canadian Sheet Steel Building Institute.

This document is copyrighted by AISI. Any redistribution is prohibited.

AISI S240-15

This Page is Intentionally Left Blank.

This document is copyrighted by AISI. Any redistribution is prohibited.

North American Standard For Cold-Formed Steel Structural Framing, 2015 Edition

vii

Section Reference Between AISI S240 and AISI S200, S210, S211, S212, S213, and S214
AISI S240
Section
A.

Title
GENERAL

A1
A1.1
A1.2
A1.2(a)
A1.2(b)
A1.2(c)
A1.2(d)
A1.3
A1.4
A1.5
A1.6
A1.7

Scope

A2
A2.1

Source
Standard
S200 to S214

Section
A

S200 to S214
S200
S200 to S214
S210
S211 and S212
S213
S214
new
S210 to S212
S200 to S214
S200 to S214
S200 to S214

A1
A1
A1
A1
A1
A1
A1

Definitions
Terms

S200 to S214
S200

A2
A2

Material

S200

A4
A4.1
A4.2
A4.3
A4.4
A4.5
A4.6

Corrosion Protection

S200
S200
S200
S200
S200
S200
S200

A4
A4.1
A4.2
A4.3
A4.4
A4.5
A4.6

A5
A5.1
A5.2
A5.3
A5.4
A5.5

Products
Base Steel Thickness
Minimum Flange Width
Product Designator
Manufacturing Tolerances
Product Identification

S200
S200
S200
S200
S200
S200

A5
A5.1
A5.2
A5.3
A5.4
A5.5

Referenced Documents

S200 to S214

varies

DESIGN

S210 to S212

B1
B1.1
B1.1.1

General
Loads and Load Combinations
Live Load Reduction on Wall Studs
Wind Loading Considerations for Wall Studs in
U.S. and Mexico
Design Basis

new (editorial)
S210 to S214
new

n/a
varies
n/a

S211
S210 and S211

A3.1
B

B1.1.2
B1.2

This document is copyrighted by AISI. Any redistribution is prohibited.

A1
A1
A1
A1

viii

AISI S240-15

Section Reference Between AISI S240 and AISI S200, S210, S211, S212, S213, and S214
AISI S240
Section

Source
Standard

Title

B1.2.1
B1.2.2
B1.2.3
B1.2.4
B1.2.4.1
B1.2.4.2
B1.2.4.3
B1.2.5
B1.2.6
B1.3

Load Path
Principles of Mechanics
Built-Up Section Design

B1.3.1
B1.3.2
B1.4
B1.5
B1.5.1
B1.5.1.1
B1.5.1.2
B1.5.1.3
B1.5.1.4
B1.5.2
B1.5.3
B1.5.4
B1.5.5
B1.5.6

Properties of Sections
Connection Design
Screw Connections
Steel-to-Steel Screws
Sheathing Screws
Spacing and Edge Distance
Gypsum Board
Welded Connections
Bolts
Power-Actuated Fasteners
Other Connectors
Connection to Other Materials

B2
B2.1
B2.2
B2.2.1
B2.2.1.1
B2.2.1.2
B2.2.2
B2.2.3
B2.2.4
B2.2.5
B2.3
B2.3.1
B2.3.2
B2.3.2.1
B2.3.2.2
B2.3.3

Floor Joists, Ceiling Joists and Roof Rafters

Wall Studs
In-Line Framing
Sheathing Span Capacity

Floor and Ceiling Framing

Scope
Floor Joist Design
Bending
Lateral-Torsional Buckling
Distortional Buckling
Shear
Web Crippling
Bending and Shear
Bending and Web Crippling
Ceiling Joist Design
Tension
Compression
Yielding, Flexural, Flexural-Torsional and Torsional
Buckling
Distortional Buckling
Bending

Section

S213 and S214

S210
S211
S200
S200
S200
S200
S200
S213
S213
S210
S211
S211
S211
S210 and S211
S211
S200
S200
S200
S200
S200
S200
S200
new
S200
S200

B1
B1
B1
C1
C2
C2.3.2
C2.4.2
C2.5.2
C1
B2
B1.5
B1.7
B1.7
B1.7
B1.1
B2.1
D1
D1.1
D1.2
D1.5
D1.6
D2
D3.1

new (editorial)
new (editorial)
new (editorial)
new (editorial)
S210
new
S210
S210
S210
S210
new (editorial)
S210
new (editorial)

n/a
n/a
n/a
n/a
B1.2.1
n/a
B1.2.2
B1.2.3
B1.2.4
B1.2.5
n/a
B1.3.1
n/a

S210
new
new (editorial)

B1.3.1
n/a
n/a

This document is copyrighted by AISI. Any redistribution is prohibited.

D3.2
D3.3

North American Standard For Cold-Formed Steel Structural Framing, 2015 Edition

Section Reference Between AISI S240 and AISI S200, S210, S211, S212, S213, and S214
AISI S240
Section

Source
Standard

Title

Section

B2.3.3.1
B2.3.3.2
B2.3.4
B2.3.5
B2.3.6
B2.3.7
B2.3.8
B2.4
B2.5
B2.5.1
B2.6
B2.7

Lateral-Torsional Buckling
Distortional Buckling
Shear
Web Crippling
Axial Load and Bending
Bending and Shear
Bending and Web Crippling
Floor Truss Design
Bearing Stiffeners
Clip Angle Bearing Stiffeners
Bracing Design
Floor Diaphragm Design

S210
new
S210
S210
S210
S210
S210
S210
S210
S210
S210
S210

B1.3.2
n/a
B1.3.3
B1.3.4
B1.3.5
B1.3.6
B1.3.7
B2
B3.1
B3.1.1
B4
B5

B3
B3.1
B3.2
B3.2.1

new (editorial)
new (editorial)
new (editorial)
new (editorial)

n/a
n/a
n/a
n/a

B3.2.1.1
B3.2.1.2
B3.2.2
B3.2.2.1
B3.2.2.2
B3.2.3
B3.2.4
B3.2.5
B3.2.5.1
B3.2.5.2
B3.3
B3.3.1
B3.3.2
B3.3.3
B3.3.4
B3.3.5
B3.4
B3.4.1
B3.5

Wall Framing
Scope
Wall Stud Design
Axial Strength [Resistance]
Yielding, Flexural, Flexural-Torsional and Torsional
Buckling
Distortional Buckling
Bending
Lateral-Torsional Buckling
Distortional Buckling
Shear
Axial Load and Bending
Web Crippling
Stud-to-Track Connection for C-Section Studs
Deflection Track Connection for C-Section Studs
Header Design
Back-to-Back Headers
Box Headers
Double L-Headers
Single L-Headers
Inverted L-Header Assemblies
Bracing
Intermediate Brace Design
Serviceability

S211
new
new (editorial)
S211
MS09-3A
S211
S211
S211
S211
S211
S212
S212
S212
S212
S212
S212
S211
S211
S211

B1.2
n/a
n/a
B1.3
n/a
B1.4
B1.5
B1.6
B2.2
B2.3
B
B1
B2
B3
B4
B5
B3
B3.1
B4

B4
B4.1
B4.2
B4.2.1
B4.2.2
B4.2.2.1

Roof Framing
Scope
Roof Rafter Design
Tension
Compression
Yielding, Flexural, Flexural-Torsional and Torsional

new (editorial)
new (editorial)
new (editorial)
S210
new (editorial)
S210

n/a
n/a
n/a
B1.4.1
n/a
B1.4.1

This document is copyrighted by AISI. Any redistribution is prohibited.

AISI S240-15

Section Reference Between AISI S240 and AISI S200, S210, S211, S212, S213, and S214
AISI S240
Section

Source
Standard

Title

Section

Buckling
B4.2.2.2
B4.2.3
B4.2.3.1
B4.2.3.2
B4.2.4
B4.2.5
B4.2.6
B4.2.7
B4.2.8
B4.3
B4.4
B4.5
B4.6

Distortional Buckling
Bending
Lateral-Torsional Buckling
Distortional Buckling
Shear
Web Crippling
Axial Load and Bending
Bending and Shear
Bending and Web Crippling
Roof Truss Design
Bearing Stiffeners
Bracing Design
Roof Diaphragm Design

new
new (editorial)
S210
new
S210
S210
S210
S210
S210
S210
S210
S210
S210

n/a
n/a
B1.4.2
n/a
B1.4.3
B1.4.4
B1.4.5
B1.4.6
B1.4.7
B2
B3.1
B4
B5

B5
B5.1
B5.2
B5.2.1
B5.2.1.1
B5.2.1.2
B5.2.2
B5.2.2.1
B5.2.2.2
B5.2.3
B5.2.4
B5.2.5
B5.3
B5.4
B5.4.1
B5.4.2
B5.4.3
B5.4.4
B5.4.5

Lateral Force-Resisting Systems

Scope
Shear Wall Design
General
Type I Shear Walls
Type II Shear Walls
Nominal Strength [Resistance]
Type I Shear Walls
Type II Shear Walls
Available Strength [Factored Resistance]
Collectors and Anchorage
Design Deflection
Strap Braced Wall Design
Diaphragm Design
General
Nominal Strength
Available Strength
Design Deflection
Beam Diaphragm Tests for Non-Steel Sheathed
Assemblies

new (editorial)
new (editorial)
S213
S213
S213
S213

n/a
n/a
C
C1
C2
C3

S213
S213
S213
S213
S213
S213
S213
S213
S213
S213
S213

C2
C3
C2
C3.3
C2.1.1
C4
D
D1
D2
D2
D2

S213

INSTALLATION

S200 to S212

General

S210 to S212

C2
C2.1
C2.2
C2.3

Member Condition
Web Holes
Cutting and Patching
Splicing

S200
S200
S200
S200

B2
B2.1
B2.2.1
B2.2.2

This document is copyrighted by AISI. Any redistribution is prohibited.

North American Standard For Cold-Formed Steel Structural Framing, 2015 Edition

Section Reference Between AISI S240 and AISI S200, S210, S211, S212, S213, and S214
AISI S240
Section

Source
Standard

Title

C3
C3.1
C3.2
C3.3
C3.3.1
C3.3.2
C3.3.4
C3.3.5
C3.4
C3.4.1
C3.4.2
C3.4.3
C3.4.4
C3.4.5
C3.4.6
C3.5
C3.5.1
C3.5.2
C3.5.3
C3.6
C3.6.1
C3.6.2
C3.6.3

Structural Framing
Foundation
Ground Contact
Floors
Plumbness and Levelness
Alignment
Bearing Width
Web Separation
Walls
Straightness, Plumbness and Levelness
Alignment
Stud-to-Track Connection
Back-to-Back and Box Headers
Double and Single L-Headers
Inverted L-Header Assemblies
Roofs and Ceilings
Plumbness and Levelness
Alignment
End Bearing
Lateral Force-Resisting Systems
Shear Walls
Strap Braced Walls
Diaphragms

C4
C4.1
C4.1.1
C4.1.2
C4.1.3
C4.2

Section

S200
S200
S200
S200
S200
S200
S200
S200

C2
C2.1
C2.2
C2.3
C2.3.1
C2.3.2, C2.3.3
C2.3.4
C2.3.5

S200
S200
S211
S212
S212
S212
S200
S200
S200
S200

C2.4.1
C2.4.2, C2.4.3
C1
C1
C2
C3
C2.5
C2.5.1
C2.5.2, C2.5.3
C2.5.4

S213
n/a
S213

Connections
Screw Connections
Steel-to-Steel Screws
Installation
Stripped Screws
Welded Connections

S200
S200
S200
S200
S200

D1
D1.1
D1.3
D1.4
D2

C5
C5.1
C5.1.1
C5.1.2
C5.1.3
C5.2
C5.2.1
C5.2.2

Miscellaneous
Utilities
Holes
Plumbing
Electrical
Insulation
Mineral Fiber Insulation
Other Insulation

S200
S200
S200
S200
S200
S200
S200
S200

E
E1
E1.1
E1.2
E1.3
E2
E2.1
E2.2

QUALITY CONTROL AND QUALITY ASSURANCE

new

n/a

TRUSSES

S214

A-G

This document is copyrighted by AISI. Any redistribution is prohibited.

xii

AISI S240-15

Section Reference Between AISI S240 and AISI S200, S210, S211, S212, S213, and S214
AISI S240
Section

Source
Standard

Title

Section

E1
E1.1

General
Scope and Limits of Applicability

S214
S214

A
A1

Truss Responsibilities

S214

E4
E4.1
E4.2
E4.3
E4.4
E4.5
E4.6
E4.7

Truss Design
Materials
Corrosion Protection
Analysis
Member Design
Gusset Plate Design
Connection Design
Serviceability

S214
S214
S214
S214
S214
S214
S214
S214

D
D1
D2
D3
D4
D5
D6
D7

E5
E5.1
E5.2
E5.3

Quality Criteria for Steel Trusses

Manufacturing Quality Criteria
Member Identification
Assembly

S214
S214
S214
S214

E
E1
E2
E3

E6
E6.1

Truss Installation
Installation Tolerances

S214
S214

F
F1

E7
E7.1
E7.2
E7.3

Test-Based Design
Component Structural Performance Load Test
Full-Scale Confirmatory Load Test
Full-Scale Structural Performance Load Test

new (editorial)
S214
S214
S214

G1
G2
G3

TESTING

new

n/a

Truss Components and Assemblies

new

n/a

APPENDIX 1

CONTINUOUSLY BRACED DESIGN FOR

DISTORTIONAL BUCKLING RESISTANCE

new

n/a

APPENDIX 2

TEST METHODS FOR TRUSS COMPONENTS AND

ASSEMBLIES

new

2.1
2.2
2.3

Component Structural Performance Load Test

Full-Scale Confirmatory Load Test
Full Scale Structural Performance Load Test

S214
S214
S214

This document is copyrighted by AISI. Any redistribution is prohibited.

G1
G2
G3

North American Standard For Cold-Formed Steel Structural Framing, 2015 Edition

AISI COMMITTEE ON FRAMING STANDARDS

Richard Haws, Chairman

Nucor Corporation

Steve Fox, Vice Chairman

Canadian Sheet Steel Building Institute

Helen Chen, Secretary

American Iron and Steel Institute

Don Allen

Super Stud Building Products

Bill Babich

Alpine TrusSteel

Brad Cameron

Cameron & Associates Engineering, LLC

Randy Daudet

Simpson Strong-Tie

Jim DesLaurier
Scott Douglas
Nader Elhajj

Certified Steel Stud Association

National Council of Structural Engineers Associations
FrameCAD Solutions

Pat Ford

Steel Framing Industry Association

Jeff Klaiman

ADTEK Engineers

Roger LaBoube

Wei-Wen Yu Center for Cold-Formed Steel Structures

Rob Madsen

Supreme Steel Framing System Association

Cris Moen
Kenneth Pagano

Virginia Polytechnic Institute and State University

Scosta Corporation

Mike Pellock

Aegis Metal Framing

Nabil Rahman

The Steel Network, Inc.

Greg Ralph

ClarkDietrich Building Systems

Ben Schafer

Johns Hopkins University

Fernando Sesma

California Expanded Metal Products

Sutton Stephens

Pacific Northwest Engineering, Inc.

Steven Walker

Light Gauge Steel Engineering Group, Inc.

Robert Wessel

Gypsum Association

Lei Xu

University of Waterloo

Cheng Yu
Rahim Zadeh

University of North Texas

Steel Stud Manufacturers Association

Ron Ziemian

Structural Stability Research Council

This document is copyrighted by AISI. Any redistribution is prohibited.

xiii

xiv

AISI S240-15

GENERAL PROVISIONS SUBCOMMITTEE

Don Allen, Chairman

Super Stud Building Products

Helen Chen, Secretary

American Iron and Steel Institute

Bill Babich

Alpine TrusSteel

Randy Daudet

Simpson Strong-Tie

Jim DesLaurier
Scott Douglas

Certified Steel Stud Association

National Council of Structural Engineers Associations

Nader Elhajj

FrameCAD Solutions

Pat Ford

Steel Framing Industry Association

Douglas Fox

TotalJoist by iSPAN Systems

Steve Fox

Canadian Sheet Steel Building Institute

Richard Haws

Nucor Corporation

Jeff Klaiman

ADTEK Engineers

Roger LaBoube

Wei-Wen Yu Center for Cold-Formed Steel Structures

Stephen Linch

Telling Industries

Rob Madsen

Supreme Steel Framing System Association

Brian McGloughlin

MBA Building Supplies

Kenneth Pagano
Greg Ralph

Scosta Corporation
ClarkDietrich Building Systems

Ben Schafer

Johns Hopkins University

Fernando Sesma

California Expanded Metal Products

Robert Wessel

Gypsum Association

Rahim Zadeh

Steel Stud Manufacturers Association

Michael Zeeuw

Quail Run Building Materials, Inc.

This document is copyrighted by AISI. Any redistribution is prohibited.

North American Standard For Cold-Formed Steel Structural Framing, 2015 Edition

DESIGN METHODS SUBCOMMITTEE

Roger LaBoube, Chairman

Wei-Wen Yu Center for Cold-Formed Steel Structures

Helen Chen, Secretary

American Iron and Steel Institute

Don Allen
Bill Babich

Super Stud Building Products

Alpine TrusSteel

Brad Cameron

Cameron & Associates Engineering, LLC

Jim DesLaurier

Certified Steel Stud Association

Nader Elhajj

FrameCAD Solutions

Pat Ford

Steel Framing Industry Association

Douglas Fox

TotalJoist by iSPAN Systems

Steve Fox

Canadian Sheet Steel Building Institute

Perry Green

Bechtel Power Corporation

Jeff Klaiman

ADTEK Engineers

Yanqi Li

Tongji University

Stephen Linch
Rob Madsen

Telling Industries
Supreme Steel Framing System Association

Brian McGloughlin

MBA Building Supplies

Cris Moen

Virginia Polytechnic Institute and State University

Robert Paullus

National Council of Structural Engineers Associations

Mike Pellock

Aegis Metal Framing

Nabil Rahman

The Steel Network, Inc.

Greg Ralph

ClarkDietrich Building Systems

Ben Schafer

Johns Hopkins University

Reynaud Serrette

Santa Clara University

Fernando Sesma

California Expanded Metal Products

Randy Shackelford

Simpson Strong-Tie

Sutton Stephens
Lei Xu

Pacific Northwest Engineering, Inc.

University of Waterloo

Cheng Yu

University of North Texas

Rahim Zadeh

Steel Stud Manufacturers Association

This document is copyrighted by AISI. Any redistribution is prohibited.

xvi

AISI S240-15

LATERAL DESIGN SUBCOMMITTEE

Rob Madsen, Chairman

Supreme Steel Framing System Association

Helen Chen, Secretary

American Iron and Steel Institute

Don Allen

Super Stud Building Products

Brad Cameron

Cameron & Associates Engineering, LLC

Nader Elhajj

FrameCAD Solutions

Bill Gould

Hilti, Inc.

Perry Green

Bechtel Power Corporation

Rick Haws

Nucor Corporation

Roger LaBoube

Wei-Wen Yu Center for Cold-Formed Steel Structures

Stephen Linch

Telling Industries

Cris Moen
J.R. Mujagic

Virginia Polytechnic Institute and State University

Uzun & Case Engineers LLC

Ashwin Mupparapu

Structuneering, Inc.

Robert Paullus

National Council of Structural Engineers Associations

Nabil Rahman

The Steel Network, Inc.

Greg Ralph

ClarkDietrich Building Systems

Colin Rogers

McGill University

Ben Schafer

Johns Hopkins University

Reynaud Serrette

Santa Clara University

Fernando Sesma

California Expanded Metal Products

Randy Shackelford

Simpson Strong-Tie

K.S. Sivakumaran
Chia-Ming Uang

McMaster University
University of California, San Diego

Lei Xu

University of Waterloo

Henry Yektai

Paco Steel Engineering

Cheng Yu

University of North Texas

Rahim Zadeh

Steel Stud Manufacturers Association

This document is copyrighted by AISI. Any redistribution is prohibited.

North American Standard For Cold-Formed Steel Structural Framing, 2015 Edition

STANDARD PRACTICES SUBCOMMITTEE

Jeff Klaiman, Chairman
Helen Chen, Secretary
Don Allen
Bill Babich
Darden Cobb
Randy Daudet
Jim DesLaurier
Nader Elhajj
Pat Ford
Kirk Grundahl
Stephen Linch
Rob Madsen
Brian McGloughlin
Kenneth Pagano
Robert Paullus
Mike Pellock
Nabil Rahman
Greg Ralph
Fernando Sesma
Tom Sputo
Steven Walker
Rahim Zadeh

ADTEK Engineers
American Iron and Steel Institute
Super Stud Building Products
ITW Building Components Group
Loadmaster Systems, Inc.
Simpson Strong-Tie
Certified Steel Stud Association
FrameCAD Solutions
Steel Framing Industry Association
SBCA Cold-Formed Steel Council
Telling Industries
Supreme Steel Framing System Association
MBA Building Supplies
Scosta Corporation
National Council of Structural Engineers Associations
Aegis Metal Framing
The Steel Network, Inc.
ClarkDietrich Building Systems
California Expanded Metal Products
Steel Deck Institute
Light Gauge Steel Engineering Group, Inc.
Steel Stud Manufacturers Association

This document is copyrighted by AISI. Any redistribution is prohibited.

xvii

xviii

AISI S240-15

TRUSS DESIGN SUBCOMMITTEE

Bill Babich, Chairman

ITW Building Components Group

Helen Chen, Secretary

American Iron and Steel Institute

Brad Cameron

Cameron & Associates Engineering, LLC

Scott Douglas

National Council of Structural Engineers Associations

Nader Elhajj
Perry Green

FrameCAD Solutions
Bechtel Power Corporation

Kirk Grundahl

SBCA Cold-Formed Steel Council

Jeff Klaiman

ADTEK Engineers

Roger LaBoube

Wei-Wen Yu Center for Cold-Formed Steel Structures

Stephen Linch

Telling Industries

Kenneth Pagano

Scosta Corporation

Anwar Merchant

Keymark

Cris Moen

Virginia Polytechnic Institute and State University

Kenneth Pagano

Scosta Corporation

Mike Pellock

Aegis Metal Framing

Randy Shackelford

Simpson-Strong Tie

Steven Walker
Lei Xu

Light Gauge Steel Engineering Group, Inc.

University of Waterloo

This document is copyrighted by AISI. Any redistribution is prohibited.

North American Standard For Cold-Formed Steel Structural Framing, 2015 Edition

xix

SYMBOLS
Symbol

Definition

Section

Gross cross-sectional area of chord member, in square inches

(mm2)

B5.2.5, B5.4.4.1

Gross area of the clip angle bearing stiffener

B2.5.1

a
a

Distance between center line of braces

Wall aspect ratio

B2.6, B4.5
B5.2.2.3.2.1

Length of the shear wall, in inches (mm)

B5.2.5

Diaphragm depth parallel to direction of load, in inches

(mm)

B5.4.4.1

Effective width determined in accordance with Section B2.1

of AISI S100 [CSA S136] with f=Fy, k=4 and w=Wmin

E4.5.1

Web crippling coefficient

B3.2.5.1

Uplift anchorage force contributed from each level, lbs [kN] B5.2.4.2.2

Uplift anchorage force, lbs [kN]

B5.2.4.2.3

Boundary chord force (tension/compression), lbs [kN]

B5.3.4.2

Shear resistance adjustment factor from Table B5.2.2.2-1.

For intermediate values of opening height ratio and
percentages of full-height sheathing, the shear resistance
adjustment factors are permitted to be determined by
interpolation.

B5.2.2.2, B5.2.4.1.2,
B5.2.4.2.3

Bending coefficient dependent on moment gradient

E4.4.2.2

Web slenderness coefficient

B3.2.5.1

End moment coefficient in interaction formula

E4.4.2.1

Bearing length coefficient

B3.2.5.1

Inside bend radius coefficient

B3.2.5.1

Length of cope

E4.6.2.1

Dead load

B1.2.2.4, B5.2.2.3.3

Depth of C-shape section

B2.6, B4.5

Depth of cope

E4.6.2.1

Modulus of elasticity of steel = 29,500,000 psi (203,000 MPa)

B5.2.5, B5.4.4.1

Design end or slip gap (distance between stud web at end of

stud and track web)

B3.2.5.2.2

This document is copyrighted by AISI. Any redistribution is prohibited.

AISI S240-15

SYMBOLS
Symbol

Definition

Section

Eccentricity of compression force with respect to the

centroid of the full section of the web member

E4.4.4.1

EIw

Sheathing bending rigidity

1.3

Concentrated design load [factored load]

B2.6, B4.5

Furring channels

A5.3.1

B2.6, B4.5

Critical buckling stress

E4.4.2.2

Mean value of the fabrication factor

B5.4.5

Yield strength of clip angle

B2.5.1

Design yield strength of track material

B3.2.5.2.2

Yield strength used for design

B1.2.1.1, B3.3.3.1.1,
B3.3.4.1.1, E4.4.2.2

Specified minimum yield strength

E4.5.1

Yield stress of steel sheet sheathing

B5.2.2.3.2.1

Fuf

Minimum tensile strength of framing materials

B5.2.2.3.2.1

Fush

Tensile strength of steel sheet sheathing

B5.2.2.3.2.1

Fut

Tensile strength of the track

B3.2.5.1

Shear modulus of sheathing material, in pounds per square

inch (MPa)

B5.2.5, B5.4.4.1

Depth of flat portion of stud web measured along plane of

web

B3.2.5.1

Height of the shear wall, ft. [m]

B5.2.1.1, B5.2.1.2,
B5.2.2.1, B5.2.4.2.2,
B5.2.4.2.3

Wall height, in inches (mm)

B5.2.5

Strap braced wall height, feet [m]

B5.3.4.2

Flat width of web of section being coped

E4.6.2.1

Height of a wall pier

B5.2.1.1

Imin

Moment of inertia determined with respect to an axis

parallel to the web of the chord member

E4.6.2.1

This document is copyrighted by AISI. Any redistribution is prohibited.

North American Standard For Cold-Formed Steel Structural Framing, 2015 Edition

xxi

SYMBOLS
Symbol

Definition

Section

Effective length

B3.2.1.1, E4.4.2.1

Effective length factor for torsion

B3.2.1.1, E4.4.2.1,
E4.4.2.2

Effective length factor for buckling about x-axis

B3.2.1.1, E4.4.2.1,
E4.4.2.2

Effective length factor for buckling about y-axis

B3.2.1.1, E4.4.2.1,
E4.4.2.2

Rotational stiffness

B2.2.1.2, B2.3.2.2,
B2.3.3.2, B3.2.1.2,
B3.2.2.2, B4.2.2.2,
B4.2.3.2, 1.1, 1.2, 1.3

Connection rotational restraint

1.3

Sheathing rotational restraint

1.3

Angle or L-header

A5.3.1

Live load

B1.2.2.4

Span length

B3.3.3.1.1

Length of Type I shear wall, feet [m]

B5.2.4.1.1

Length of Type I shear wall including anchor offsets, feet [m]

B5.2.4.2.2

Length of strap braced wall including anchor offsets, feet [m]

B5.3.4.2

Diaphragm length perpendicular to direction of load, in

inches (mm)

B5.4.4.1

Unbraced length of the compression web member

E4.4.4.1

Length of truss

E6.1.1

Leff

Average length between the last rows of fasteners of

adjacent truss members in the connection

E4.5.1

Vertical leg dimension of angle

B3.3.3.1.1, B3.3.3.1.2

Distance between braces

B2.2.1.2, B2.3.2.2,
B2.3.3.2, B3.2.1.2,
B3.2.2.2, B4.2.2.2,
B4.2.3.2

Unbraced length of compression member for torsion

B3.2.1.1, E4.4.2.1,
E4.4.2.2

Unbraced length of compression member for bending

about x-axis

B3.2.1.1, E4.4.2.1,
E4.4.2.2

Unbraced length of compression member for bending

about y-axis

B3.2.1.1, E4.4.2.1,
E4.4.2.2

This document is copyrighted by AISI. Any redistribution is prohibited.

xxii

AISI S240-15

SYMBOLS
Symbol

Definition

Section

L1, L2

One-half joist spacing to the first and second sides

respectively, as illustrated in Figure B8.2-1

1.3

Required flexural strength

B3.3.2.5

Mean value of the material factor

B5.4.5

Nominal flexural strength defined in Section C3.1 of AISI

S100 [CSA S136]

B3.3.2.5

Nominal flexural strength [resistance] defined in Section C3.1

of AISI S100 [CSA S136]

B3.3.2.5

Nominal flexural strength [resistance]

E4.4.2.2

Mng

Gravity nominal flexural strength [moment resistance]

B3.3.3.1.1, B3.3.3.1.2,
B3.3.4.1.1

Mnu

Nominal uplift flexural strength [moment resistance]

B3.3.3.1.2

Mnxo

Nominal flexural strength [resistance] determined at f = Fy

E4.4.2.3

Required flexural strength [moment due to factored loads]

B3.3.2.5

Required flexural strength

E4.4.2.3

Required flexural strength [moment of factored loads]

E4.4.2.3

Distance from shear center to mid-plane of web

B2.6, B4.5

Stud bearing length

B3.2.5.1

Number of chord splices in diaphragm (considering both

diaphragm chords)

B5.4.4.1

Number of connections in the assembly with the same

tributary area

B5.4.5

Required web crippling strength

B3.3.2.5

Required compressive axial strength

E4.4.2.3

End two-flange web crippling capacity of the floor joist

B2.5.1

Required lateral force

B2.6, B4.5

Nominal web crippling strength [resistance]

B3.3.2.3

Nominal web crippling strength determined in accordance

with Section B3.3.2.3

B3.3.2.5

Nominal web crippling strength [resistance] computed by

Section B3.3.2.3
Nominal shear strength [resistance] of screw connections

B3.3.2.5

B5.2.2.3.2.1

This document is copyrighted by AISI. Any redistribution is prohibited.

North American Standard For Cold-Formed Steel Structural Framing, 2015 Edition

xxiii

SYMBOLS
Symbol

Definition

Section

within the effective strip width, We, on the steel sheet

sheathing
Nominal axial strength [resistance] based on Section C4.1 of
AISI S100 [CSA S136]. Only flexural buckling need be
considered.

E4.4.4.1

Nominal axial compressive strength [resistance]

E4.5

Pno

Nominal axial strength [resistance] determined at f = Fy

E4.4.2.3

Pndt

Nominal strength [resistance] of a single deflection track

subjected to transverse loads and connected to its support at
a fastener spacing not greater than the stud spacing

B3.2.5.2.2

Pnst

Nominal strength for the stud-to-track connection when

subjected to transverse loads

B3.2.5.1, B3.2.5.2.1

Pnst

Nominal web crippling strength [resistance]

B3.2.5.2.1

Interior two-flange web crippling capacity of the rim track

B2.5.1

Required web crippling strength [compression force due to

factored loads]

B3.3.2.5

Required compressive axial strength [axial force of factored

loads]

E4.4.2.3

Seismic response modification coefficient

A1.3

Stud inside bend radius

B3.2.5.1

Uplift factor

B3.3.3.1.2

Required concentrated load strength

E4.4.2.3

Modification factor

E4.4.4

Reduction factor

E4.6.2.1

Required concentrated load strength [factored concentrated

load]

E4.4.2.3

RdRo

Seismic force modification factors

A1.3

Nominal interior one-flange loading web crippling strength

[resistance]

E4.4.2.3

Radius of gyration of the full section about the minor axis

E4.4.4.1

Snow load

B1.2.2.4

Stud or joist framing member which has lips

A5.3.1

Center-to-center spacing of studs

B3.2.5.2.2

This document is copyrighted by AISI. Any redistribution is prohibited.

xxiv

AISI S240-15

SYMBOLS
Symbol

Definition

Section

Elastic section modulus of effective section calculated relative

to extreme compression fiber at Fc

E4.4.2.2

Elastic section modulus of effective section calculated relative

to extreme compression fiber at Fy

E4.4.2.2

Sec

Elastic section modulus of the effective section calculated at

f = Fy in the extreme compression fibers

B3.3.3.1.1, B3.3.4.1.1

Nominal shear strength [resistance]

B5.4.5

Specified standard term load based on snow or occupancy

loads acting alone or in combination

B5.2.2.3.3

s
s

Maximum fastener spacing at panel edges, in inches (mm)

Screw spacing on the panel edges

B5.2.5, B5.4.4.1
B5.2.2.3.2.1

T
Tsh
Tf
t
t

Track section
Design thickness of steel sheet sheathing
Minimum design thicknesses of framing members
Design thickness of steel sheet sheathing
Stud design thickness

A5.3.1
B5.2.2.3.2.1
B5.2.2.3.2.1
B5.2.2.3.2.1
B3.2.5.1

Design thickness

B3.3.3.1.2

Design thickness of gusset plate

E4.5.1

Design thickness of section being coped

E4.6.2.1

Design thickness of the C-shape section

B3.3.2.3

Track design thickness

B3.2.5.1, B3.2.5.2.2

Track design thickness

B3.3.2.3, B3.2.5.1

tsheathing

Nominal panel thickness, in inches (mm)

B5.2.5, B5.4.4.1

tstud

Framing designation thickness, in inches (mm)

B5.2.5, B5.4.4.1

Channel or stud framing section which does not have lips

A5.3.1

Shear force in Type I shear wall, lbs [kN]

B5.2.4.1.1, B5.2.4.1.2,
B5.2.4.2.2

Shear force in Type II shear wall, lbs [kN]

B5.2.4.2.3

Total lateral load applied to the shear wall, in pounds (N)

B5.2.5

Shear force in strap braced wall, lbs [KN]

B5.3.4.2

Total lateral load applied to the diaphragm, in pounds (N)

B5.4.4.1

Coefficient of variation of fabrication factor

B5.4.5

This document is copyrighted by AISI. Any redistribution is prohibited.

North American Standard For Cold-Formed Steel Structural Framing, 2015 Edition

xxv

SYMBOLS
Symbol

Definition

Section

Coefficient of variation of material factor

B5.4.5

Nominal strength [resistance] for shear

B5.2.1.2, B5.2.2.1,
B5.2.2.2

Actual calculated coefficient of variation of the test results,

without limit

B5.4.5

Coefficient of variation of the load effect

B5.4.5

Nominal strength [resistance] per unit length as specified in

Section B5.2.2.3, lbs./ft. [kN/m]

B5.2.2.1, B5.2.2.2

Unit shear force, plf [kN/m]

B5.2.4.1.1, B5.2.4.1.2

Shear demand, in pounds per linear inch (N/mm) = V/b

B5.2.5

Shear demand, in pounds per linear inch (N/mm) = V/(2b)

B5.4.4.1

W
we

Wind load
Effective width

B1.2.2.4
B5.2.2.3.2.1

Lesser of the actual gusset plate width or Whitmore section

E4.5.1

Uniform design load [factored load]

B2.6, B4.5

Length of the shear wall, ft. [m]

B5.2.1.1, B5.2.1.2,
B5.2.2.1

Length of a wall pier

B5.2.1.1

wdt

Effective track length

B3.2.5.2.2

wst

20 tt + 0.56

B3.2.5.1

Distance between the ith chord-splice and the nearest

support, in inches (mm)

B5.4.4.1

Distance from concentrated load to brace

B2.6, B4.5

Coefficient for conversion of units

B3.2.5.1, B3.2.5.2.2,
B3.3.2.3

Parameter determined in accordance with Equation

B3.3.2.3-1 or B3.3.2.3-2

B3.3.2.3

Ratio of the average load per fastener based on a nonuniform fastener pattern to the average load per fastener
based on a uniform fastener pattern (= 1 for a uniformly
fastened diaphragm)
Variables

B5.4.4.1

, 1, 2

B5.2.2.3.2.1

This document is copyrighted by AISI. Any redistribution is prohibited.

xxvi

AISI S240-15

SYMBOLS
Symbol

Definition

Section

Factor used on deflection calculation

B5.2.5, B5.4.4.1

Target reliability index

B5.4.5

1, 2, 3

Variables

B5.2.2.3.2.1

Factor used on deflection calculation

Variable

B5.2.5, B5.4.4.1
B5.2.2.3.2.1

Calculated deflection, in inches (mm)

B5.2.5

Deflection of blocked diaphragm determined in accordance

with Eq. B5.4.4-1

B5.4.4.2, B5.4.4,
B5.4.4.1

Deflection of an unblocked diaphragm

B5.4.4.2

Vertical deformation of anchorage/attachment details, in

inches (mm)

B5.2.5

Sum of lengths of Type II shear wall segments, ft. [m]

B5.2.2.2, B5.2.4.1.2,
B5.2.4.2.3

Deformation value associated with ith chord splice, in

inches (mm)

B5.4.4.1

1, 2, 3,
4

Factors used in deflection calculation

B5.2.5, B5.4.4.1

Resistance factor

B3.2.5.1, B3.2.5.2.1,
B3.2.5.2.2, B3.3.2.3,
B3.3.2.5, B3.3.3.1.1,
B3.3.3.1.2, B3.3.4.1.1,
B5.2.3, E4.4.2.3

Resistance factor

B2.5.1, E4.5.1

Resistance factor

B5.2.3, B5.4.3

Safety factor

B3.2.5.1, B3.2.5.2.1,
B3.2.5.2.2, B3.3.2.3,
B3.3.2.5, B3.3.3.1.1,
B3.3.3.1.2, B3.3.4.1.1,
B5.2.3, E4.4.2.3

Safety factor

B2.5.1, E4.5.1

Safety factor

B5.2.3, B5.4.3

This document is copyrighted by AISI. Any redistribution is prohibited.

North American Standard For Cold-Formed Steel Structural Framing, 2015 Edition

xxvii

TABLE OF CONTENTS
NORTH AMERICAN STANDARD
FOR COLD-FORMED STEEL STRUCTURAL FRAMING
Disclaimer ................................................................................................................................................... ii
Preface ......................................................................................................................................................... v
Section Reference Between AISI S240 and AISI S200, S210, S211, S212, S213, and S214................vii
AISI Committee on Framing Standards............................................................................................... xiii
General Provisions Subcommittee ........................................................................................................ xiv
Design Methods Subcommittee ............................................................................................................. xv
Lateral Design Subcommittee ............................................................................................................... xvi
Standard Practices Subcommittee .......................................................................................................xvii
Truss Design Subcommittee ............................................................................................................... xviii
NORTH AMERICAN STANDARD FOR COLD-FORMED STEEL STRUCTURAL FRAMING ...................... 1
A. GENERAL ......................................................................................................................................... 1
A1 Scope...................................................................................................................................................... 1
A2 Definitions ............................................................................................................................................ 1
A2.1 Terms .............................................................................................................................................. 1
A3 Material ................................................................................................................................................. 8
A4 Corrosion Protection ........................................................................................................................... 8
A5 Products ................................................................................................................................................ 9
A5.1 Base Steel Thickness ..................................................................................................................... 9
A5.2 Minimum Flange Width .............................................................................................................. 9
A5.3 Product Designator ...................................................................................................................... 9
A5.4 Manufacturing Tolerances .......................................................................................................... 9
A5.5 Product Identification ................................................................................................................ 11
A5.5.1 Identification of Groups of Like Members ................................................................. 11
A5.5.2 Identification of Individual Framing Members ......................................................... 11
A6 Reference Documents ....................................................................................................................... 11
B. DESIGN ..........................................................................................................................................14
B1 General ................................................................................................................................................ 14
B1.1 Loads and Load Combinations................................................................................................. 14
B1.1.1 Application of Live Load Reduction on Wall Studs ................................................. 14
B1.1.2 Application of Wind Loads on Wall Studs in the United States and Mexico........ 14
B1.2 Design Basis................................................................................................................................. 14
B1.2.1 Floor Joists, Ceiling Joists and Roof Rafters ............................................................... 14
B1.2.2 Wall Studs ....................................................................................................................... 15
B1.2.3 In-Line Framing.............................................................................................................. 16
B1.2.4 Sheathing Span Capacity .............................................................................................. 16
B1.2.5 Load Path ........................................................................................................................ 16
B1.2.6 Principles of Mechanics................................................................................................. 17
B1.3 Built-Up Section Design ............................................................................................................ 17
B1.4 Properties of Sections ................................................................................................................. 17
B1.5 Connection Design ..................................................................................................................... 17
B1.5.1 Screw Connections ......................................................................................................... 18
B1.5.1.1 Steel-to-Steel Screws.......................................................................................... 18
B1.5.1.2 Sheathing Screws ............................................................................................... 18
B1.5.1.3 Spacing and Edge Distance .............................................................................. 18
B1.5.1.4 Gypsum Board ................................................................................................... 18
This document is copyrighted by AISI. Any redistribution is prohibited.

xxviii

AISI S240-15

B1.5.2 Welded Connections...................................................................................................... 18

B1.5.3 Bolts.................................................................................................................................. 18
B1.5.4 Power-Actuated Fasteners ............................................................................................ 18
B1.5.5 Other Connectors ........................................................................................................... 18
B1.5.6 Connection to Other Materials ..................................................................................... 19
B2 Floor and Ceiling Framing ............................................................................................................... 19
B2.1 Scope............................................................................................................................................. 19
B2.2 Floor Joist Design........................................................................................................................ 19
B2.2.1 Bending............................................................................................................................ 19
B2.2.1.1 Lateral-Torsional Buckling ............................................................................... 19
B2.2.1.2 Distortional Buckling ........................................................................................ 19
B2.2.2 Shear ................................................................................................................................ 19
B2.2.3 Web Crippling ................................................................................................................ 20
B2.2.4 Bending and Shear ......................................................................................................... 20
B2.2.5 Bending and Web Crippling......................................................................................... 20
B2.3 Ceiling Joist Design .................................................................................................................... 20
B2.3.1 Tension ............................................................................................................................ 20
B2.3.2 Compression ................................................................................................................... 20
B2.3.2.1 Yielding, Flexural, Flexural-Torsional and Torsional Buckling .................. 20
B2.3.2.2 Distortional Buckling ........................................................................................ 20
B2.3.3 Bending............................................................................................................................ 20
B2.3.3.1 Lateral-Torsional Buckling .............................................................................. 20
B2.3.3.2 Distortional Buckling ....................................................................................... 21
B2.3.4 Shear ................................................................................................................................ 21
B2.3.5 Web Crippling ................................................................................................................ 21
B2.3.6 Axial Load and Bending ............................................................................................... 21
B2.3.7 Bending and Shear ......................................................................................................... 21
B2.3.8 Bending and Web Crippling......................................................................................... 21
B2.4 Floor Truss Design ..................................................................................................................... 21
B2.5 Bearing Stiffeners........................................................................................................................ 22
B2.5.1 Clip Angle Bearing Stiffeners ....................................................................................... 22
B2.6 Bracing Design ............................................................................................................................ 23
B2.7 Floor Diaphragm Design ........................................................................................................... 24
B3 Wall Framing...................................................................................................................................... 24
B3.1 Scope............................................................................................................................................. 24
B3.2 Wall Stud Design ........................................................................................................................ 24
B3.2.1 Available Axial Strength [Factored Resistance] ........................................................ 24
B3.2.1.1 Yielding, Flexural, Flexural-Torsional and Torsional Buckling .................. 24
B3.2.1.2 Distortional Buckling ........................................................................................ 25
B3.2.2 Bending............................................................................................................................ 25
B3.2.2.1 Lateral-Torsional Buckling ............................................................................... 25
B3.2.2.2 Distortional Buckling ........................................................................................ 26
B3.2.3 Shear ................................................................................................................................ 26
B3.2.4 Axial Load and Bending ............................................................................................... 26
B3.2.5 Web Crippling ................................................................................................................ 26
B3.2.5.1 Stud-to-Track Connection for C-Section Studs ............................................. 26
B3.2.5.2 Deflection Track Connection for C-Section Studs......................................... 30
B3.3 Header Design ............................................................................................................................ 31

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xxix

B3.3.1 Back-to-Back Headers.................................................................................................... 31

B3.3.1.1 Bending ............................................................................................................... 31
B3.3.1.2 Shear .................................................................................................................... 31
B3.3.1.3 Web Crippling.................................................................................................... 31
B3.3.1.4 Bending and Shear ............................................................................................ 31
B3.3.1.5 Bending and Web Crippling ............................................................................ 31
B3.3.2 Box Headers .................................................................................................................... 32
B3.3.2.1 Bending ............................................................................................................... 32
B3.3.2.2 Shear .................................................................................................................. 32
B3.3.2.3 Web Crippling.................................................................................................... 32
B3.3.2.4 Bending and Shear ............................................................................................ 32
B3.3.2.5 Bending and Web Crippling ............................................................................ 32
B3.3.3 Double L-Headers .......................................................................................................... 33
B3.3.3.1 Bending ............................................................................................................... 34
B3.3.3.1.1 Gravity Loading ................................................................................... 34
B3.3.3.1.2 Uplift Loading ...................................................................................... 34
B3.3.3.2 Shear .................................................................................................................... 35
B3.3.3.3 Web Crippling.................................................................................................... 35
B3.3.3.4 Bending and Shear ............................................................................................ 35
B3.3.3.5 Bending and Web Crippling ............................................................................ 35
B3.3.4 Single L-Headers ............................................................................................................ 35
B3.3.4.1 Bending ............................................................................................................... 35
B3.3.4.1.1 Gravity Loading ................................................................................... 35
B3.3.4.1.2 Uplift Loading ...................................................................................... 36
B3.3.4.2 Shear .................................................................................................................... 36
B3.3.4.3 Web Crippling.................................................................................................... 36
B3.3.4.4 Bending and Shear ............................................................................................ 36
B3.3.4.5 Bending and Web Crippling ............................................................................ 36
B3.3.5 Inverted L-Header Assemblies .................................................................................... 36
B3.4 Bracing ......................................................................................................................................... 37
B3.4.1 Intermediate Brace Design............................................................................................ 37
B3.5 Serviceability ............................................................................................................................... 37
B4 Roof Framing...................................................................................................................................... 37
B4.1 Scope............................................................................................................................................. 37
B4.2 Roof Rafter Design ..................................................................................................................... 37
B4.2.1 Tension ............................................................................................................................ 37
B4.2.2 Compression ................................................................................................................... 37
B4.2.2.1 Yielding, Flexural, Flexural-Torsional and Torsional Buckling .................. 37
B4.2.2.2 Distortional Buckling ........................................................................................ 37
B4.2.3 Bending............................................................................................................................ 38
B4.2.3.1 Lateral-Torsional Buckling ............................................................................... 38
B4.2.3.2 Distortional Buckling ........................................................................................ 38
B4.2.4 Shear ................................................................................................................................ 38
B4.2.5 Web Crippling ................................................................................................................ 38
B4.2.6 Axial Load and Bending ............................................................................................... 38
B4.2.7 Bending and Shear ......................................................................................................... 39
B4.2.8 Bending and Web Crippling......................................................................................... 39
B4.3 Roof Truss Design ...................................................................................................................... 39

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B4.4 Bearing Stiffeners........................................................................................................................ 39

B4.5 Bracing Design ............................................................................................................................ 39
B4.6 Roof Diaphragm Design ............................................................................................................ 40
B5 Lateral Force-Resisting Systems ...................................................................................................... 40
B5.1 Scope............................................................................................................................................. 40
B5.2 Shear Wall Design ...................................................................................................................... 40
B5.2.1 General ............................................................................................................................ 40
B5.2.1.1 Type I Shear Walls............................................................................................. 40
B5.2.1.2 Type II Shear Walls ........................................................................................... 41
B5.2.2 Nominal Strength [Resistance]..................................................................................... 41
B5.2.2.1 Type I Shear Walls............................................................................................. 41
B5.2.2.2 Type II Shear Walls ........................................................................................... 41
B5.2.2.3 Nominal Strength [Resistance] per Unit Length ........................................... 42
B5.2.2.3.1 General Requirements ......................................................................... 42
B5.2.2.3.2 Steel Sheet Sheathing ........................................................................... 43
B5.2.2.3.2.1 Effective Strip Method ........................................................... 43
B5.2.2.3.3 Wood Structural Panel Sheathing...................................................... 44
B5.2.2.3.4 Gypsum Board Panel Sheathing ........................................................ 45
B5.2.2.3.5 Fiberboard Panel Sheathing ............................................................... 45
B5.2.2.3.6 Combined Systems .............................................................................. 45
B5.2.3 Available Strength [Factored Resistance] ................................................................... 50
B5.2.4 Collectors and Anchorage ............................................................................................ 50
B5.2.4.1 Collectors and Anchorage for In-Plane Shear ............................................... 50
B5.2.4.1.1 Type I Shear Walls ............................................................................... 50
B5.2.4.1.2 Type II Shear Walls .............................................................................. 50
B5.2.4.2 Uplift Anchorage at Wall Ends....................................................................... 50
B5.2.4.2.1 General .................................................................................................. 51
B5.2.4.2.2 Type I Shear Walls ............................................................................... 51
B5.2.4.2.3 Type II Shear Walls .............................................................................. 51
B5.2.4.3 Uplift Anchorage Between Type II Shear Wall Ends ................................... 51
B5.2.5 Design Deflection ........................................................................................................... 51
B5.3 Strap Braced Wall Design .......................................................................................................... 53
B5.3.1 General ............................................................................................................................ 53
B5.3.2 Nominal Strength [Resistance]..................................................................................... 53
B5.3.3 Available Strength [Factored Resistance] ................................................................... 53
B5.3.4 Collectors and Anchorage ............................................................................................ 53
B5.3.4.1 Collectors and Anchorage for In-Plane Shear ............................................... 53
B5.3.4.2 Uplift Anchorage at Wall Ends........................................................................ 53
B5.3.5 Design Deflection ........................................................................................................... 54
B5.4 Diaphragm Design ..................................................................................................................... 54
B5.4.1 General ............................................................................................................................ 54
B5.4.2 Nominal Strength ........................................................................................................... 55
B5.4.3 Available Strength ......................................................................................................... 55
B5.4.4 Design Deflection ........................................................................................................... 55
B5.4.4.1 Blocked Diaphragms ......................................................................................... 56
B5.4.4.2 Unblocked Diaphragms.................................................................................... 56
B5.4.5 Beam Diaphragm Tests for Non-Steel Sheathed Assemblies .................................. 57

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C. INSTALLATION ...............................................................................................................................58
C1 General ................................................................................................................................................ 58
C2 Material Condition ............................................................................................................................ 58
C2.1 Web Holes.................................................................................................................................... 58
C2.2 Cutting and Patching ................................................................................................................. 58
C2.3 Splicing......................................................................................................................................... 58
C3 Structural Framing ............................................................................................................................ 58
C3.1 Foundation .................................................................................................................................. 58
C3.2 Ground Contact .......................................................................................................................... 59
C3.3 Floors ............................................................................................................................................ 59
C3.3.1 Plumbness and Levelness ............................................................................................. 59
C3.3.2 Alignment ....................................................................................................................... 59
C3.3.3 Bearing Width................................................................................................................. 59
C3.3.4 Web Separation .............................................................................................................. 59
C3.4 Walls ............................................................................................................................................. 59
C3.4.1 Straightness, Plumbness and Levelness ..................................................................... 59
C3.4.2 Alignment ....................................................................................................................... 59
C3.4.3 Stud-to-Track Connection ............................................................................................. 59
C3.4.4 Back-to-Back and Box Headers .................................................................................... 60
C3.4.5 Double and Single L-Headers ...................................................................................... 60
C3.4.6 Inverted L-Header Assemblies .................................................................................... 60
C3.5 Roofs and Ceilings...................................................................................................................... 62
C3.5.1 Plumbness and Levelness ............................................................................................. 62
C3.5.2 Alignment ....................................................................................................................... 62
C3.5.3 End Bearing..................................................................................................................... 62
C3.6 Lateral Force-Resisting Systems ............................................................................................... 62
C3.6.1 Shear Walls ..................................................................................................................... 62
C3.6.2 Strap Braced Walls ......................................................................................................... 62
C3.6.3 Diaphragms .................................................................................................................... 62
C4 Connections ........................................................................................................................................ 62
C4.1 Screw Connections ..................................................................................................................... 63
C4.1.1 Steel-to-Steel Screws ...................................................................................................... 63
C4.1.2 Installation ...................................................................................................................... 63
C4.1.3 Stripped Screws .............................................................................................................. 63
C4.2 Welded Connections .................................................................................................................. 63
C5 Miscellaneous ..................................................................................................................................... 63
C5.1 Utilities ......................................................................................................................................... 63
C5.1.1 Holes ................................................................................................................................ 63
C5.1.2 Plumbing ......................................................................................................................... 63
C5.1.3 Electrical .......................................................................................................................... 63
C5.2 Insulation ..................................................................................................................................... 64
C5.2.1 Mineral Fiber Insulation................................................................................................ 64
C5.2.2 Other Insulation ............................................................................................................. 64
D. QUALITY CONTROL AND QUALITY ASSURANCE ...........................................................................65
D1 General ................................................................................................................................................ 65
D1.1 Scope and Limits of Applicability ............................................................................................ 65
D1.2 Responsibilities ........................................................................................................................... 65
D2 Quality Control Programs ................................................................................................................ 65

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AISI S240-15

D3 Quality Control Documents ............................................................................................................. 66

D3.1 Documents to be Submitted ...................................................................................................... 66
D3.1.1 Additional Requirements for Lateral Force-Resisting Systems............................... 66
D3.1.1.1 Component Assemblies .................................................................................... 66
D3.1.1.2 Other Than Component Assemblies............................................................... 66
D3.1.1.3 Exceptions to Sections D3.1.1.1 and D3.1.1.2 ................................................. 66
D3.2 Available Documents ................................................................................................................. 66
D4 Quality Assurance Agency Documents ......................................................................................... 67
D5 Inspection Personnel ......................................................................................................................... 67
D5.1 Quality Control Inspector.......................................................................................................... 67
D5.2 Quality Assurance Inspector..................................................................................................... 68
D6 Inspection Tasks................................................................................................................................. 68
D6.1 General ......................................................................................................................................... 68
D6.2 Quality Control Inspection Tasks............................................................................................. 68
D6.3 Quality Assurance Inspection Tasks........................................................................................ 68
D6.4 Coordinated Inspection ............................................................................................................. 69
D6.5 Material Verification .................................................................................................................. 69
D6.6 Inspection of Welding ................................................................................................................ 70
D6.7 Inspection of Mechanical Fastening......................................................................................... 71
D6.8 Inspection of Cold-Formed Steel Light-Frame Construction ............................................... 72
D6.9 Additional Requirements for Lateral Force-Resisting Systems ........................................... 72
D6.9.1 Fit-up of Welds ............................................................................................................... 73
D7 Nonconforming Material and Workmanship................................................................................ 74
D7.1 Additional Inspections............................................................................................................... 74
D7.2 Rejection of Material .................................................................................................................. 74
E. TRUSSES........................................................................................................................................75
E1 General ................................................................................................................................................ 75
E1.1 Scope and Limits of Applicability ............................................................................................ 75
E2 Truss Responsibilities ....................................................................................................................... 75
E3 Loading ............................................................................................................................................... 75
E4 Truss Design ....................................................................................................................................... 75
E4.1 Materials ...................................................................................................................................... 75
E4.2 Corrosion Protection .................................................................................................................. 75
E4.3 Analysis........................................................................................................................................ 75
E4.4 Member Design........................................................................................................................... 75
E4.4.1 Properties of Sections .................................................................................................... 75
E4.4.2 Compression Chord Members ..................................................................................... 76
E4.4.3 Tension Chord Members .............................................................................................. 79
E4.4.4 Compression Web Members ........................................................................................ 79
E4.4.5 Tension Web Members.................................................................................................. 79
E4.4.6 Eccentricity in Joints ...................................................................................................... 80
E4.5 Gusset Plate Design .................................................................................................................... 80
E4.6 Connection Design ..................................................................................................................... 81
E4.6.1 Fastening Methods......................................................................................................... 81
E4.6.2 Coped Connections for C-Shaped Sections ................................................................ 81
E4.7 Serviceability ............................................................................................................................... 82
E5 Quality Criteria for Steel Trusses .................................................................................................... 82
E5.1 Manufacturing Quality Criteria ............................................................................................... 82

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North American Standard For Cold-Formed Steel Structural Framing, 2015 Edition

xxxiii

E5.2 Member Identification ............................................................................................................... 82

E5.3 Assembly ..................................................................................................................................... 82
E6 Truss Installation ............................................................................................................................... 83
E6.1 Installation Tolerances ............................................................................................................... 83
E6.1.1 Straightness ..................................................................................................................... 83
E6.1.2 Plumbness ....................................................................................................................... 83
E6.1.3 Top Chord Bearing Trusses .......................................................................................... 83
E7 Test-Based Design ............................................................................................................................. 83
F. TESTING .........................................................................................................................................85
F1 General ................................................................................................................................................ 85
F2 Truss Components and Assemblies ................................................................................................ 85
APPENDIX 1, CONTINUOUSLY BRACED DESIGN FOR DISTORTIONAL BUCKLING RESISTANCE.....86
APPENDIX 2, TEST METHODS FOR TRUSS COMPONENTS AND ASSEMBLIES ................................89
2.1 Component Structural Performance Load Test............................................................................. 89
2.1.1 Flexural Test ................................................................................................................................ 89
2.1.1.1 Number of Test Specimens ........................................................................................... 89
2.1.1.2 Materials .......................................................................................................................... 89
2.1.1.3 Test Apparatus ............................................................................................................... 89
2.1.1.4 Load and Deflection Measuring Devices.................................................................... 89
2.1.1.5 Loading Procedures ....................................................................................................... 89
2.1.1.6 Interpretation of Test Results ....................................................................................... 89
2.1.1.7 Report .............................................................................................................................. 89
2.1.2 Compression Test ....................................................................................................................... 90
2.2 Full-Scale Confirmatory Load Test ................................................................................................. 90
2.2.1 Test Specimen ............................................................................................................................. 90
2.2.2 Number of Test Specimens ....................................................................................................... 90
2.2.3 Materials ...................................................................................................................................... 90
2.2.4 Fabrication ................................................................................................................................... 90
2.2.5 Test Apparatus ............................................................................................................................ 90
2.2.6 Load and Deflection Measuring Devices ................................................................................ 91
2.2.7 Loading Procedures ................................................................................................................... 91
2.2.7.1 Tests to Confirm Deflection .......................................................................................... 91
2.2.7.2 Tests to Confirm Available Strength [Factored Resistance] Assumptions ............ 91
2.2.8 Interpretation of Test Results.................................................................................................... 92
2.2.9 Report ........................................................................................................................................... 92
2.3 Full-Scale Structural Performance Load Test ................................................................................ 92
2.3.1 Test Specimen ............................................................................................................................. 92
2.3.2 Number of Test Specimens ....................................................................................................... 92
2.3.3 Materials ...................................................................................................................................... 92
2.3.4 Fabrication ................................................................................................................................... 92
2.3.5 Test Apparatus ............................................................................................................................ 92
2.3.6 Load and Deflection Measuring Devices ................................................................................ 93
2.3.7 Loading Procedures ................................................................................................................... 93
2.3.8 Interpretation of Test Results.................................................................................................... 93
2.3.9 Report ........................................................................................................................................... 94

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This Page is Intentionally Left Blank.

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North American Standard For Cold-Formed Steel Structural Framing, 2015 Edition

NORTH AMERICAN STANDARD

FOR COLD-FORMED STEEL STRUCTURAL FRAMING
A. GENERAL
A1 Scope
A1.1 This Standard applies to the design and installation of structural members and connections
utilized in cold-formed steel light-frame construction applications.
A1.2 The design and installation of cold-formed steel framing for the following systems shall be
in accordance with AISI S100 [CSA S136] and this Standard:
(a) floor and roof systems in buildings,
(b) structural walls in buildings,
(c) shear walls, strap braced walls and diaphragms to resist in-plane lateral loads, and
(d) trusses for load-carrying purposes in buildings.
A1.3 Cold-formed steel structural members and connections in seismic force-resisting systems and
diaphragms shall be designed in accordance with the additional provisions of AISI S400 in
the following cases:
(a) In the U.S. and Mexico, in seismic design categories (SDC) D, E, or F, or wherever the
seismic response modification coefficient, R, used to determine the seismic design forces
is taken other than 3.
(b) In Canada, where the design spectral response acceleration S(0.2) as specified in the
NBCC is greater than 0.12 and the seismic force modification factors, RdRo, used to
determine the seismic design forces, are taken as greater than or equal to 1.56.
A1.4 Cold-formed steel framing for floor and roof systems, and structural walls, as listed in
items A1.2(a) and A1.2(b), are also permitted to be designed solely in accordance with
AISI S100 [CSA S136].
A1.5 Elements not specifically addressed by this Standard shall be constructed in accordance
with applicable building code requirements.
A1.6 This Standard does not preclude the use of other materials, assemblies, structures or
designs not meeting the criteria herein, when the other materials, assemblies, structures
or designs demonstrate equivalent performance for the intended use to those specified in
this Standard. Where there is a conflict between this Standard and other reference
documents, the requirements contained within this Standard shall govern.
A1.7 This Standard includes Chapters A through F and Appendices 1 and 2 in their entirety.
A2 Definitions
A2.1 Terms
Where the following terms appear in this Standard in italics, they shall have the meaning
herein indicated. Terms included in square brackets shall be specific to LSD terminology.
Where a country is indicated in square brackets following the definition, the definition shall
apply only in the country indicated. Terms not defined in Section A2.1 shall have the
ordinary accepted meaning for the intended context.
Adjusted Shear Resistance. In Type II shear walls, the unadjusted shear resistance multiplied by

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AISI S240-15

the shear resistance adjustment factor.

Allowable Strength. Nominal strength divided by the safety factor Rn/. [USA and Mexico]
Applicable Building Code. The building code under which the building is designed.
Approved. Acceptable to the authority having jurisdiction.
ASD (Allowable Strength Design). Method of proportioning structural components such that the
allowable strength equals or exceeds the required strength of the component under the action
of the ASD load combinations. [USA and Mexico]
ASD Load Combination. Load combination in the applicable building code intended for allowable
strength design (allowable stress design). [USA and Mexico]
Authority Having Jurisdiction. An organization, political subdivision, office, or individual
charged with the responsibility of administering and enforcing the provisions of the
applicable building code.
Available Strength. Design strength or allowable strength, as appropriate. [USA and Mexico]
Base Steel Thickness. The thickness of bare steel exclusive of all coatings.
Bearing Stiffener. Additional material that is attached to the web to strengthen the member
against web crippling. Also called a web stiffener.
Blocking. C-shaped member, break shape, flat strap material, or component assemblies attached
to structural members, flat strap or sheathing panels to transfer shear forces or stabilize
members.
Blocking, Panel. Blocking that transmits shear between the panels of a shear wall or diaphragm.
Blocking, Stud. Blocking that provides torsional restraint to the studs in a shear wall.
Bracing. Structural elements that are installed to provide restraint or support (or both) to
other structural members or nonstructural members so that the complete assembly forms a
stable structure.
Ceiling Joist. A horizontal structural member that supports ceiling components and which may
be subject to attic loads.
Chord. Member of a shear wall, strap braced wall or diaphragm that forms the perimeter, interior
opening, discontinuity or re-entrant corner.
Chord Member. A structural member that forms the top or bottom component of a truss.
Chord Splice. The connection region between two truss chord members where there is no change
in slope.
Chord Stud. Axial load-bearing studs located at the ends of Type I shear walls or Type II shear
wall segments or strap braced walls.
Clip Angle. An L-shaped short piece of steel typically used for connections.
Cold-Formed Sheet Steel. Sheet steel or strip steel that is manufactured by (1) press braking
blanks sheared from sheets or cut length of coils or plates, or by (2) continuous roll
forming of cold- or hot-rolled coils of sheet steel; both forming operations are performed
at ambient room temperature, that is, without any addition of heat such as would be
required for hot forming.
Cold-Formed Steel. See Cold-Formed Sheet Steel.
Collector. Also known as a drag strut, a member parallel to the applied load that serves to
transfer forces between diaphragms and members of the lateral force-resisting system or
distributes forces within the diaphragm.
Component. See Structural Component.
Component Assembly. A fabricated assemblage which consists primarily of cold-formed steel
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North American Standard For Cold-Formed Steel Structural Framing, 2015 Edition

structural members that is manufactured by the component manufacturer.

Component Manufacturer. The individual or organization responsible for the manufacturing of
component assemblies for the project. Also referred to as truss manufacturer on projects
involving trusses, but hereinafter will be referred to as component manufacturer.
Connection. Combination of structural elements and joints used to transmit forces between
two or more members.
Connector. A device used to transmit forces between cold-formed steel structural members, or
between a cold-formed steel structural member and another structural element.
Contractor. Owner of the building, or the person that contracts with the owner, who constructs
or manages the construction of the building in accordance with the construction documents.
Also referred to as owners representative for construction, but hereinafter will be referred
to as contractor.
Construction Documents. Written, graphic and pictorial documents prepared or assembled for
describing the design (including the structural system), location and physical
characteristics of the elements of a building necessary to obtain a building permit and
construct a building.
Cripple Stud. A stud that is placed between a header and a window or door head track, a header
and wall top track, or a window sill and a bottom track to provide a backing to attach
finishing and sheathing material.
C-Shape. A cold-formed steel shape used for structural members and nonstructural members
consisting of a web, two (2) flanges and two (2) lips (edge stiffeners).
Curtain Wall. A wall that transfers transverse (out-of-plane) loads and is limited to a
superimposed vertical load, exclusive of sheathing materials, of not more than 100 lb/ft
(1.46 kN/m), or a superimposed vertical load of not more than 200 lbs (0.890 kN).
Deflection Track. A track manufactured with extended flanges and used at the top of a wall to
provide for vertical movement of the structure, independent of the wall stud.
Design Load. Applied load determined in accordance with either LRFD load combinations or
ASD load combinations, whichever is applicable. [USA and Mexico]
Design Strength. Resistance factor multiplied by the nominal strength. [USA and Mexico]
Design Thickness. The steel thickness used in design.
Designation Thickness. The minimum base steel thickness expressed in mils and rounded to a
whole number.
Diaphragm. Roof, floor or other membrane or bracing system that transfers in-plane forces to
the lateral force-resisting system.
Eave Overhang. The horizontal projection of the roof measured from the outside face of
exterior wall framing to the outside edge of the roof.
Edge Stiffener. See Lip.
Factored Load. Product of a load factor and the nominal load [specified load].
Factored Resistance. Product of nominal resistance and appropriate resistance factor. [Canada]
Fiberboard. A fibrous, homogeneous panel made from lignocellulosic fibers (usually wood or
cane) and having a density of less than 31 pounds per cubic foot (pcf) (497 kg/m3) but
more than 10 pcf (160 kg/m3).
Flange. For a C-shape, U-shape or track, that portion of the structural member or nonstructural
member that is perpendicular to the web. For a furring channel, that portion of the
structural member or nonstructural member that connects the webs.

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AISI S240-15

Floor Joist. A horizontal structural member that supports floor loads and superimposed vertical
loads.
Girt. Horizontal structural member that supports wall panels and is primarily subjected to
bending under horizontal loads, such as wind load.
Grade. The designation of the minimum yield strength.
Gusset Plate. A structural member used to facilitate the connection of truss chord or web members
at a heel, ridge, other pitch break, or panel point.
Hat-Shape. A singly symmetric shape consisting of at least two vertical webs and a horizontal
stiffened flange which is used as a chord member in a truss.
Header. A horizontal structural member used over floor, roof or wall openings to transfer loads
around the opening to supporting structural members.
Heel. The connection region between the top and bottom truss chords of a non-parallel chord
truss.
Hold-Down (Tie-Down). A device used to resist overturning forces in a shear wall or strap braced
wall, or uplift forces in a cold-formed steel structural member.
Inspection. When used in conjunction with quality control and quality assurance, it shall mean
the systematic examination and review of the work for compliance with the appropriate
documents, with appropriate subsequent documentation.
Installation Drawings. Drawings that show the location and installation of the cold-formed steel
structural framing. Also referred to as truss placement diagram for truss construction.
Installer. Party responsible for the installation of cold-formed steel light-frame construction.
Jack Stud. A stud that does not span the full height of the wall and provides bearing for
headers.
Joist. A structural member primarily used in floor and ceiling framing.
King Stud. A stud, adjacent to a jack stud, that spans the full height of the wall and supports
vertical and lateral loads.
Lateral Force-Resisting System. The structural elements and connections required to resist
racking and overturning due to wind forces or seismic forces, or other predominantly
horizontal forces, or combination thereof, imposed upon the structure in accordance with
the applicable building code.
Light-Frame Construction. Construction where the vertical and horizontal structural elements
are primarily formed by a system of repetitive cold-formed steel or wood framing members.
Limit States. Those conditions in which a structural member ceases to fulfill the function for
which it was designed. Those states concerning safety are called the ultimate limit states.
The ultimate limit state for strength is the maximum load-carrying capacity. Limit states
that restrict the intended use of a member for reasons other than safety, such as deflection
and vibration, are called serviceability limit states. [Canada]
Lip. That part of a structural or nonstructural member that extends from the flange as a stiffening
element.
Load. Force or other action that results from the weight of building materials, occupants and
their possessions, environmental effects, differential movement, or restrained
dimensional changes.
Load Effect. Forces, stresses, and deformations produced in a structural component by the
applied loads.
Load Factor. Factor that accounts for deviations of the actual load from the nominal load, for

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North American Standard For Cold-Formed Steel Structural Framing, 2015 Edition

uncertainties in the analysis that transforms the load into a load effect, and for the
probability that more than one extreme load will occur simultaneously. [USA and Mexico]
LRFD (Load and Resistance Factor Design). Method of proportioning structural components such
that the design strength equals or exceeds the required strength of the component under the
action of the LRFD load combinations. [USA and Mexico]
LRFD Load Combination. Load combination in the applicable building code intended for strength
design (Load and Resistance Factor Design). [USA and Mexico]
LSD (Limit States Design). Method of proportioning structural components (members,
connectors, connecting elements and assemblages) such that no applicable limit state is
exceeded when the structure is subjected to all appropriate load combinations. [Canada]
Mean Roof Height. The average of the roof eave height and the height to the highest point on
the roof surface, except that eave height shall be used for roof angles less than or equal to
10 degrees (0.18 rad).
Mil. A unit of measurement equal to 1/1000 inch.
Multiple Span. The span made by a continuous member having intermediate supports.
Nominal Load. Magnitude of the load specified by the applicable building code. [USA and
Mexico]
Nominal Resistance (Resistance). Capacity of a structure or component to resist the effects of
loads, determined in accordance with this Standard using specified material strengths and
dimensions. [Canada]
Nominal Strength. Strength of a structure or component (without the resistance factor or safety
factor applied) to resist the load effects, as determined in accordance with this Standard.
[USA and Mexico]
Nonstructural Member. A member in a steel-framed system that is not a part of the gravity
load-resisting system, lateral force-resisting system or building envelope.
Owner. The individual or entity organizing and financing the design and construction of the
project.
Panel Point. The connection region between a web member and chord member in a truss.
Pitch Break. The connection region between two truss chord members where there is a change in
slope, excluding the heel.
Plans. Also referred to as construction drawings. Drawings prepared by the building designer
for the owner of the project. These drawings include but are not limited to floor plans,
framing plans, elevations, sections, details and schedules as necessary to define the
desired construction.
Plan Aspect Ratio. The ratio of the length (longer dimension) to the width (shorter dimension)
of the building.
Punchout. A hole made during the manufacturing process in the web of a steel framing
member.
Purlin. Horizontal structural member that supports roof deck and is primarily subjected to
bending under vertical loads such as snow, wind, or dead loads.
Quality Assurance. Monitoring and inspection tasks performed by a registered design professional,
firm or approved agency other than the component manufacturer or installer to ensure that
the material provided and work performed by the component manufacturer and installer
meet the requirements of the approved construction documents and referenced standards.
Quality assurance includes those tasks designated special inspection by the applicable
building code.
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AISI S240-15

Quality Assurance Inspector. Individual or agency designated to provide quality assurance

inspection for the work being performed.
Quality Control. Controls and inspections implemented by the component manufacturer or
installer to confirm that the material provided and work performed meet the requirements
of the approved construction documents and referenced standards.
Quality Control Inspector. Individual or agency designated to perform quality control inspection
tasks for the work being performed.
Quality Control Program. Program in which the component manufacturer or installer, as
applicable, maintains detailed assembly or installation and inspection procedures to
ensure conformance with the approved installation drawings, plans, specifications and
referenced standards.
Rake Overhang. The horizontal projection of the roof measured from the outside face of a
gable endwall to the outside edge of the roof.
Rational Engineering Analysis. Analysis based on theory that is appropriate for the situation,
any relevant test data, if available, and sound engineering judgment.
Registered Design Professional. Architect or engineer who is licensed to practice their respective
design profession as defined by the legal requirements of the jurisdiction in which the
building is to be constructed.
Repetitive Framing. A framing system where the wall, floor and roof structural members are
spaced no greater than 24 inches (610 mm) on center. Larger spaces are permitted at
openings where the structural loads are transferred to headers or lintels and supporting
studs, joists or rafters.
Required Strength. Forces, stresses, and deformations produced in a structural component,
determined by either structural analysis, for the LRFD or ASD load combinations, as
appropriate, or as specified by this Standard. [USA and Mexico]
Resistance Factor (). Factor that accounts for unavoidable deviations of the actual strength
from the nominal strength [nominal resistance] and for the manner and consequences of
failure.
Ridge. The horizontal line formed by the joining of the top edges of two upward sloping roof
surfaces.
Rim Track. A horizontal structural member that is connected to the end of a floor joist.
Risk Category. A categorization of buildings and other structures for determination of flood,
wind, snow, ice, and earthquake loads based on the risk associated with unacceptable
performance.
Roof Rafter. A horizontal or sloped, structural member that supports roof loads.
Safety Factor (). Factor that accounts for the desired level of safety, including deviations of
the actual load from the nominal load and uncertainties in the analysis that transforms the
load into a load effect, in determining the nominal strength and for the manner and
consequences of failure. [USA and Mexico]
Seismic Design Category (SDC). A classification assigned by the applicable building code to a
structure based upon its risk category and the severity of the design earthquake ground
motion at the site.
Seismic Force-Resisting System. That part of the structural system that has been selected in the
design to provide energy dissipation and the required resistance to seismic forces
prescribed in the applicable building code.
Shear Wall. A wall with structural sheathing attached to cold-formed steel structural members and
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North American Standard For Cold-Formed Steel Structural Framing, 2015 Edition

designed to primarily resist lateral forces parallel to the wall.

Shop Drawings. Drawings for the production of individual component assemblies for the project.
Single Span. The span made by one continuous structural member without any intermediate
supports.
Span. The clear horizontal distance between bearing supports.
Specifications. Written instructions, which, with the plans, define the materials, standards,
design of the products, and workmanship expected on a construction project.
Specified Load. Magnitude of the load specified by the applicable building code, not including load
factors. [Canada]
Static Load. A load or series of loads that are supported by or are applied to a structure so
gradually that forces caused by change in momentum of the load and structural elements
can be neglected and all parts of the system at any instant are essentially in equilibrium.
Steel Sheet Sheathing. A panel of thin flat steel sheet.
Strap. Flat or coiled sheet steel material typically used for bracing or blocking, which transfers
loads by tension or shear.
Strap Braced Wall. A wall with strap bracing attached to cold-formed steel structural members and
designed to primarily resist lateral forces parallel to the wall.
Strap Bracing. Steel straps applied diagonally to form a vertical truss that forms part of the
lateral force-resisting system.
Structural Component. Member, connector, connecting element or assemblage.
Structural Member. A member that resists design loads [factored loads], as required by the
applicable building code, except when defined as a nonstructural member.
Structural Sheathing. The structural sheathing that is capable of distributing loads, bracing
members, and providing additional stability that strengthens the assembly.
Stud. A vertical structural member or nonstructural member in a wall system or assembly.
Track. A structural member or nonstructural member consisting of only a web and two (2) flanges.
Track web depth measurements are taken to the inside of the flanges.
Truss. A coplanar system of structural members joined together at their ends typically to
construct a series of triangles that form a stable beam-like framework.
Truss Design Drawing. Written, graphic and pictorial depiction of an individual truss.
Truss Design Engineer. Person who is licensed to practice engineering as defined by the legal
requirements of the jurisdiction in which the building is to be constructed and who
supervises the preparation of the truss design drawings.
Truss Designer. Person responsible for the preparation of the truss design drawings.
Truss Manufacturer. An individual or organization engaged in the manufacturing of site-built
or in-plant trusses.
Truss Member. A chord member or web member of a truss.
Type I Shear Wall. Wall designed to resist in-plane lateral forces that is fully sheathed and that
is provided with hold-downs at each end of the wall segment.
Type II Shear Wall. Wall designed to resist in-plane lateral forces that is sheathed with wood
structural panels or steel sheet sheathing that contains openings, but which has not been
specifically designed and detailed for force transfer around wall openings. Hold-downs for
Type II shear walls are only required at the ends of the wall.
Type II Shear Wall Segment. Section of shear wall (within a Type II shear wall) with full-height
sheathing (i.e., with no openings) and which meets specific aspect ratio limits.
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AISI S240-15

Wall Pier. A section of a Type I shear wall adjacent to an opening and equal in height to the
opening, which is designed to resist lateral forces in the plane of the wall.
Web. That portion of a structural member or nonstructural member that connects the flanges.
Web Member. A structural member in a truss that is connected to the top and bottom chords, but
is not a chord member.
Wind Exposure. Wind exposure in accordance with the applicable building code.
Wood Structural Panel. A panel manufactured from veneers, wood strands or wafers or a
combination of veneer and wood strands or wafers bonded together with waterproof
synthetic resins or other suitable bonding systems.
Yield Strength. Stress at which a material exhibits a specified limiting deviation from the
proportionality of stress to strain as defined by ASTM.
Z-Shape. A point-symmetric or non-symmetric section that is used as a chord member in a truss.
A3 Material
A3.1 Structural members utilized in cold-formed steel light-frame construction shall be coldformed to shape from sheet steel complying with the requirements of ASTM
A1003/A1003M, subject to the following limitations:
(a) Type H (high ductility): No limitations.
(b) Type L (low ductility): Limited to purlins, girts and curtain wall studs. Additional
country-specific limitations for curtain wall studs are provided in Section A2.3.5 of
AISI S100 [CSA S136].
A3.2 In Canada, structural members are permitted to be cold-formed to shape from sheet steel
complying with the requirements of ASTM A653/A653M Type SS or ASTM
A792/A792M Type SS.
A4 Corrosion Protection
A4.1 Structural members utilized in cold-formed steel light-frame construction shall have a
protective coating as specified in Table A4-1.
Table A4-1
Coating Designations
Coating
Classification

Coating
Designator

Metallic
Coated

CP 60
CP 90

Minimum Coating Requirements

Zinc Coated
2
2
oz/ft (g/m )

Zinc Iron
2
2
oz/ft (g/m )

55% Al-Zinc
2
2
oz/ft (g/m )

Zinc-5%
2
2
oz/ft (g/m )

G60 [Z180]

A60 [ZF180]

AZ50 [AZM150]

CF30 [ZGF90]

G90 [Z275]

Not Applicable

AZ50 [AZM150]

CF45 [ZGF135]

The metallic coated substrate shall meet the requirements of metallic coated.
In addition, the paint film shall have a minimum thickness of 0.5 mil per side
(primer plus topcoat) with a minimum primer thickness of 0.1 mil per side. E
A Zinc-coated steel sheet as described in ASTM A653/A653M.
B Zinc-iron alloy-coated steel sheet as described in ASTM A653/A653M.
C 55% Aluminum-zinc alloy-coated steel sheet as described in ASTM A792/A792M.
D Zinc-5% aluminum alloy-coated steel sheet as described in ASTM A875/A875M.
E In accordance with the requirements of ASTM A1003/A1003M.

Painted
Metallic

A4.1.1 In Canada, structural members utilized in cold-formed steel light-frame construction shall
have a metallic coating of G60 [Z180] complying with the requirements of ASTM
A653/A653M or AZ50 [AZM150] complying with the requirements of ASTM
A792/A792M.
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North American Standard For Cold-Formed Steel Structural Framing, 2015 Edition

A4.2 Additional corrosion protection shall not be required on edges of metallic-coated steel
framing members, where shop or field cut, punched or drilled.
A4.3 Unless additional corrosion protection is provided, framing members shall be located
within the building envelope and shielded from direct contact with moisture from the
ground or the exterior climate.
A4.4 Dissimilar metals shall not be used in direct contact with cold-formed steel framing
members unless approved for that application.
A4.5 Cold-formed steel framing members shall not be embedded in concrete unless approved for
that application.
A4.6 Fasteners shall have a corrosion-resistant treatment, or be manufactured from material
not susceptible to corrosion.
A5 Products
A5.1 Base Steel Thickness
The material thickness of framing members, in their end-use, shall meet or exceed the
minimum base steel thickness values given in the approved construction documents. In no case
shall the minimum base steel thickness be less than 95% of the design thickness.
A5.2 Minimum Flange Width
Where intended for sheathing attachment, C-shape members shall have a minimum flange
width of 1-1/4 inch (31.8 mm). For track members, the minimum flange width shall be 3/4
inch (19.1 mm).
A5.3 Product Designator
A5.3.1 A four-part product designator that identifies the size (both web depth and flange
width), type, and thickness shall be used for reference to structural members. The
product designator as described (i.e., based on U.S. Customary units) shall be used for
either U.S. Customary or SI Metric units. The product designator shall consist of the
following sequential codes:
(a) A three- or four-digit numeral indicating member web depth in 1/100 inch.
(b) A letter indicating member type, in accordance with the following:
S = Stud or joist framing member which has lips
T = Track section
U = Channel or stud framing section which does not have lips
F = Furring channels
L = Angle or L-header
(c) A three-digit numeral indicating flange width in 1/100 inch, followed by a dash.
(d) A two- or three-digit numeral indicating designation thickness.
A5.3.2 The material grade used in design shall be identified on the construction documents
and when ordering the material.
A5.4 Manufacturing Tolerances
Structural members utilized in cold-formed steel light-frame construction shall comply with the
manufacturing tolerances listed in Table A5-1, as illustrated in Figure A5-1. All
measurements shall be taken not less than 1 ft (305 mm) from the end of the member.
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AISI S240-15

Table A5-1
Manufacturing Tolerances for Structural Members
Dimension1

Item Checked

Length

Web Depth

C
D
E

1
2
3

Flare
Overbend
Hole Center
Width
Hole Center
Length

Studs, in. (mm)

Tracks, in. (mm)

+3/32 (2.38)
-3/32 (2.38)
+1/32 (0.79)
-1/32 (0.79)
+1/16 (1.59)
-1/16 (1.59)
+1/16 (1.59)
-1/16 (1.59)
+1/4 (6.35)
-1/4 (6.35)
+1/16 (1.59)
-1/16 (1.59)

+ 1/2 (12.7)
-1/4 (6.35)
+1/32 (0.79)
+1/8 (3.18)
+0 (0)
-3/32 (2.38)
NA
NA
NA
NA
+1/16 (1.59)
-1/16 (1.59)
1/32 per ft (2.60 per m)
1/2 max (12.7)

Crown

Camber

1/8 per 10 ft (3.13 per 3 m)

Bow

1/8 per 10 ft (3.13 per 3 m)

Twist

Flange
Width

Stiffening Lip
Length

1/32 per ft (2.60 per m)

1/2 max (12.7)
+1/8 (3.18)
-1/16 (1.59)
+1/8 (3.18)
-1/32 (0.79)

1/32 per ft (2.60 per m)

1/2 max (12.7)
1/32 per ft (2.60 per m)
1/2 max (12.7)
+1/4 (6.35)
-1/16 (1.59)
NA

All measurements are taken not less than 1 ft (305 mm) from the end.
Outside dimension for stud; inside for track.
1/8 inch per 10 feet represents L/960 maximum for overall camber and bow. Thus, a 20-foot-long member has
1/4 inch permissible maximum; a 5-foot-long member has 1/16-inch permissible maximum.

K
Stiffening Lip Length
J Flange Width

Figure A5-1 Manufacturing Tolerances for Structural Members

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North American Standard For Cold-Formed Steel Structural Framing, 2015 Edition

A5.5 Product Identification

Framing members used in cold-formed steel light-frame construction shall be identified in
accordance with the requirements of this section.
A5.5.1 Identification of Groups of Like Members
Groups of like members shall be marked with a label, or a tag attached thereto.
Marking shall include the roll-formers identification (name, logo, or initials), length,
quantity, and roll-formers member designator including member depth, flange size, and
minimum steel thickness in mils or inches exclusive of protective coating.
A5.5.2 Identification of Individual Framing Members
A5.5.2.1 In the United States and Mexico, in addition to the marking referenced in
A5.5.1, individual framing members shall have a legible label, stencil, or
embossment, at a maximum distance of 96 in. (2440 mm) on center, on the member,
with the following minimum information:
(a) The rollformers identification (i.e., name, logo, or initials).
(b) The minimum steel thickness, in mils or inches, exclusive of protective coating.
(c) The minimum yield strength in kips per square inch [megapascals].
(d) The appropriate protective coating designator in accordance with Section A4.
A5.5.2.2 In Canada, in addition to the marking referenced in A5.5.1, individual framing
members shall have a legible label, stencil, or embossment, at a maximum distance
of 96 in. (2440 mm) on center, on the member, with the following minimum
information:
(a) The manufacturers identification (name, logo, or initials); and
(b) The minimum steel thickness (in mils, inches or millimeters) exclusive of
protective coatings.
A6 Reference Documents
The following documents or portions thereof are referenced within this Standard and shall
be considered as part of the requirements of this document.
1. American Society of Civil Engineers, Reston, VA
ASCE 7-10 Including Supplement No. 1, Minimum Design Loads for Buildings and Other
Structures.
2. American Iron and Steel Institute, Washington, DC
AISI S100-12, North American Specification for the Design of Cold-Formed Steel Structural
Members
AISI S202-15, Code of Standard Practice for Cold-Formed Steel Structural Framing
AISI S901-13, Rotational-Lateral Stiffness Test Method for Beam-to-Panel Assemblies
AISI S902-13, Stub-Column Test Method for Effective Area of Cold-Formed Steel Columns
AISI S903-13, Standard Methods for Determination of Uniform and Local Ductility
AISI S904-13, Standard Test Methods for Determining the Tensile and Shear Strength of Screws
AISI S905-13, Test Standard for Cold-Formed Steel Connections
AISI S907-13, Test Standard for Cantilever Test Method for Cold-Formed Steel Diaphragms
AISI S909-13, Standard Test Method for Determining the Web Crippling Strength of Cold-Formed

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AISI S240-15

Steel Beams
AISI S910-13, Test Method for Distortional Buckling of Cold-Formed Steel Hat-Shaped Compression
Members
AISI S911-13, Method for Flexural Testing of Cold-Formed Steel Hat-Shaped Beams
AISI S913-13, Test Standard for Hold-Downs Attached to Cold-Formed Steel Structural Framing
AISI S914-15, Test Standard for Joist Connectors Attached to Cold-Formed Steel Structural Framing
AISI S915-15, Test Standard for Through-The-Web Punchout Cold-Formed Steel Wall Stud
Bridging Connectors
ASTM International, West Conshohocken, PA
ASTM A653/A653M-15, Standard Specification for Steel Sheet, Zinc-Coated (Galvanized) or ZincIron Alloy-Coated (Galvannealed) by the Hot-Dip Process
ASTM A792/A792M-10, Standard Specification for Steel Sheet, 55% Aluminum-Zinc AlloyCoated by the Hot-Dip Process
ASTM A875/A875M-13, Standard Specification for Steel Sheet, Zinc-5% Aluminum Alloy-Coated
by the Hot-Dip Process
ASTM A1003/A1003M-15, Standard Specification for Steel Sheet, Carbon, Metallic- and
Nonmetallic-Coated for Cold-Formed Framing Members
ASTM C208-12, Standard Specification for Cellulosic Fiber Insulating Board
ASTM C95415, Standard Specification for Steel Drill Screws for the Application of Gypsum Panel
Products or Metal Plaster Bases to Steel Studs From 0.033 in. (0.84 mm) to 0.112 in. (2.84 mm) in
Thickness
ASTM C100214, Standard Specification for Steel Self-Piercing Tapping Screws for the Application
of Gypsum Panel Products or Metal Plaster Bases to Wood Studs or Steel Studs
ASTM C1396/C1396M14a, Standard Specification for Gypsum Board
ASTM C1513-13, Standard Specification for Steel Tapping Screws for Cold-Formed Steel Framing
Connections
ASTM E455-11, Standard Method for Static Load Testing of Framed Floor or Roof Diaphragm
Constructions for Buildings
ASTM E2126-11, Standard Test Methods for Cyclic (Reversed) Load Test for Shear Resistance of
Vertical Elements of the Lateral Force Resisting Systems for Buildings
American Welding Society, Miami, FL
AWS B5.1, Specification for the Qualification of Welding Inspectors, 2003 Edition
AWS D1.3, Structural Welding Code-Sheet Steel, 2008 Edition
CSA Group, Mississauga, Ontario, Canada
CSA O325-07 (R2012), Construction Sheathing
CAN/CSA-S136-12, North American Specification for the Design of Cold-Formed Steel Structural
Members
CSA O121-08 (R2013), Douglas Fir Plywood
CSA O151-09 (R2014), Canadian Softwood Plywood
CSA O325-07(R2012), Construction Sheathing
CSA O437-93 (R2011), Standards on OSB and Waferboard
Department of Commerce Voluntary Product Standard, administered by NIST,
Gaithersburg, MD
DOC PS 1-09, Structural Plywood

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North American Standard For Cold-Formed Steel Structural Framing, 2015 Edition

DOC PS 2-10, Performance Standard for Wood-Based Structural-Use Panels

7. National Research Council of Canada, Ottawa, Ontario, Canada
NBCC 2010, National Building Code of Canada, 2010 Edition

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AISI S240-15

B. DESIGN
B1 General
The provisions in Section B1 shall be used in conjunction with the requirements in Sections
B2 through B5, as applicable.
B1.1 Loads and Load Combinations
Buildings or other structures and all parts therein shall be designed in accordance with
the applicable building code to support all loads that are expected during its life. In the absence
of an applicable building code, the loads, forces, and combinations of loads shall be in accordance
with accepted engineering practice for the location under consideration as specified by the
applicable sections of ASCE 7, Minimum Design Loads for Buildings and Other Structures in the
United States and Mexico, or the National Building Code of Canada in Canada.
B1.1.1 Application of Live Load Reduction on Wall Studs
For the purpose of calculating the design axial load on a wall using floor live load
reduction requirements in accordance with the applicable building code, the tributary area of
the wall shall be limited to the floor area assigned to the individual wall framing members.
B1.1.2 Application of Wind Loads on Wall Studs in the United States and Mexico
In the United States and Mexico, the design of the wall studs shall be based on the
following design wind loads:
(a) Combined bending and axial load effect based on Main Wind Force-Resisting System
(MWFRS) wind loads.
(b) Bending load effect based on Components and Cladding (C&C) wind loads.
(c) Deflection limits based on 42% of Components and Cladding (C&C) wind loads with no
axial loads.
B1.2 Design Basis
The proportioning, designing and detailing of cold-formed steel light-frame lateral forceresisting systems, trusses, structural members, connections and connectors shall be in accordance
with AISI S100 [CSA S136], and the reference documents except as modified or supplemented
by the requirements of this Standard.
B1.2.1 Floor Joists, Ceiling Joists and Roof Rafters
B1.2.1.1 Floor joists, ceiling joists and roof rafters shall be designed either on the basis of
discretely braced design or on the basis of continuously braced design, in accordance
with the following:
(a) Discretely Braced Design. Floor and roof assemblies using discretely braced
design shall be designed neglecting the structural bracing and composite-action
contribution of attached sheathing or deck. Discretely braced design shall
include assemblies where the sheathing or deck is not attached directly to
structural members.
(b) Continuously Braced Design. Unless noted otherwise in Section B2 or B4, the
continuously braced design requirements of this Standard shall be limited to

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North American Standard For Cold-Formed Steel Structural Framing, 2015 Edition

floor joists, ceiling joists and roof rafters that comply with all of the following
conditions:
(1) Maximum web depth = 14 inches (356 mm)
(2) Maximum design thickness = 0.1242 inches (3.155 mm)
(3) Minimum design yield strength, Fy = 33 ksi (230 MPa)
(4) Maximum design yield strength, Fy = 50 ksi (345 MPa)
B1.2.1.2 Where continuously braced design is used, the construction documents shall
identify the sheathing or deck as a structural element.
B1.2.1.3 A web with one or more holes shall be designed in accordance with AISI S100
[CSA S136], or reinforced in accordance with an approved design or as specified by a
registered design professional.
B1.2.2 Wall Studs
B1.2.2.1 Wall studs shall be designed either on the basis of all steel design or on the basis
of sheathing braced design, in accordance with the following:
(a) All Steel Design. Wall stud assemblies using all steel design shall be designed
neglecting the structural bracing and composite-action contribution of the
attached sheathings.
(b) Sheathing Braced Design. Wall stud assemblies using sheathing braced design
shall have sheathing attached to both flanges of the wall stud or sheathing
attached to the one flange and discrete bracing to the other flange. The stud shall
be connected to the bottom and top track or other horizontal member(s) of the
wall to provide lateral and torsional support to the wall stud in the plane of the
wall. Wall studs with sheathing attached to both sides that is not identical shall
be designed based on the assumption that the weaker of the two sheathings is
attached to both sides.
B1.2.2.2 When sheathing braced design is used, the construction documents shall identify
the sheathing as a structural element.
B1.2.2.3 For curtain wall studs, the combination of sheathing attached to one side of the
wall stud and discrete bracing for the other flange is permitted. The spacing of
discrete bracing shall be no greater than 8 ft (2.44 m) on center. For design, the
nominal flexural strength [resistance] shall be determined by AISI S100 Section C3.1.
When the compression flange has sheathing attached, AISI S100 Section C3.1.1 is
permitted. When the compression flange does not have sheathing attached, AISI S100
Section C3.1.2 shall apply. In both cases, AISI S100 Section C3.1.4 for distortional
buckling shall also be considered.
B1.2.2.4 In the United States and Mexico, when sheathing braced design is used, the
wall studs shall also be evaluated without the sheathing bracing for the following load
combination:
1.2D + (0.5L or 0.2S) + 0.2W
(Eq. B1.2.2-1)
where
D = Dead load
L = Live load
S = Snow load
W = Wind load
B1.2.2.5 In Canada, the provisions for sheathing braced design shall be in accordance

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AISI S240-15

with a theory, tests, or rational engineering analysis and shall comply with Chapter C
of AISI S100 [CSA S136], as applicable.
B1.2.2.6 A web with one or more holes shall be designed in accordance with AISI S100
[CSA S136].
B1.2.3 In-Line Framing
B1.2.3.1 Each joist, rafter, truss, and structural wall stud (above or below) shall be aligned
vertically in accordance with the limits depicted in Figure B1.2.3-1.
B1.2.3.2 The alignment tolerance shall not be required to be met when a structural load
distribution member is specified in accordance with the approved construction
documents.

Figure B1.2.3-1 In-Line Framing

B1.2.4 Sheathing Span Capacity

B1.2.4.1 Floor joist and floor truss spacing shall be limited by the span capacity of the
floor structural sheathing material.
B1.2.4.2 Wall stud spacing shall be limited by the span capacity of the wall structural
sheathing material.
B1.2.4.3 The spacing of roof and ceiling framing members shall be limited by the span
capacity of the ceiling or roof structural sheathing material.
B1.2.5 Load Path
A continuous load path to the foundation shall be provided for the uplift, shear, and

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North American Standard For Cold-Formed Steel Structural Framing, 2015 Edition

compression forces due to lateral wind forces, seismic forces, or other predominantly
horizontal forces, or combinations thereof, imposed upon the structure in accordance with
the applicable building code. Elements resisting forces contributed by multiple stories shall be
designed for the sum of forces contributed by each story in conformance to applicable
building code.
B1.2.6 Principles of Mechanics
Where cold-formed steel structural members and connections are not required to be
designed in accordance with the additional provisions of Section A1.3, the provisions of
this section are permitted for lateral force-resisting systems.
B1.2.6.1 The shear resistance of shear walls, strap braced walls and diaphragms is permitted
to be determined by principles of mechanics using values of fastener strength,
sheathing shear resistance, and strap strength, as applicable.
B1.2.6.2 When determined by the principles of mechanics, the nominal strength [nominal
resistance] defines the maximum resistance that the diaphragm, shear wall, or strap
braced wall is capable of developing.
B1.2.6.3 Required strength [effect of factored loads] shall be determined in accordance with
the force requirements in the applicable building code.
B1.2.6.4 When determined by the principles of mechanics, values for systems defined in
this Standard shall be scaled to the values in this Standard.
B1.3 Built-Up Section Design
Built-up sections shall be evaluated in accordance with Section D1 of AISI S100 [CSA
S136] and the additional requirements of Sections B1.3.1 and B1.3.2, as applicable.
B1.3.1 For either all steel design or sheathing braced design, the available strength [factored
resistance] of built-up sections shall be determined in accordance with Section D1.2 of
AISI S100 [CSA S136].
Exception: Where a built-up axial load bearing section comprised of two studs oriented
back-to-back forming an I-shaped cross-section is seated in a track in accordance
with the requirements of Section C3.4.3 and the top and bottom end bearing detail
of the studs consists of support by steel or concrete components with adequate
strength and stiffness to preclude relative end slip of the two built-up stud
sections, the compliance with the end connection provisions of AISI S100 Section
D1.2(b) is not required.
B1.3.2 When the connection requirements of Section D1.2 of AISI S100 [CSA S136] or the
exception permitted in B1.3.1 are not met, the available strength [factored resistance] of
built-up sections shall be equal to the sum of the available strengths [factored resistances]
of the individual members of the built-up cross-section.
B1.4 Properties of Sections
The properties of sections shall be full cross-section properties, except where use of a
reduced cross-section or effective design width is required by AISI S100 [CSA S136].
B1.5 Connection Design
Connections using screws, welds, bolts, or power-actuated fasteners shall be designed in
accordance with AISI S100 [CSA S136] and the additional requirements of this Standard. For
connections using other fastener types, design values [factored resistances] shall be determined
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AISI S240-15

by testing in accordance with Section F1 of AISI S100 [CSA S136].

B1.5.1 Screw Connections
B1.5.1.1 Steel-to-Steel Screws
Screw fasteners for steel-to-steel connections shall be in compliance with ASTM C1513
or the approved construction documents.
B1.5.1.2 Sheathing Screws
Screw fasteners for structural sheathing to steel connections shall be in compliance with
ASTM C1513 or the approved construction documents.
B1.5.1.3 Spacing and Edge Distance
B1.5.1.3.1 For screw fasteners in steel-to-steel connections to be considered fully
effective, the minimum edge distance shall be 3 times the nominal diameter.
Exception: Where the edge is parallel to the direction of the applied force, the
minimum edge distance of screw fasteners shall be 1.5 times the nominal
diameter.
B1.5.1.3.2 For screw fasteners in steel-to-steel connections to be considered fully
effective, the minimum center-to-center spacing shall be 3 times the nominal
diameter.
Exception: Where the center-to-center spacing of screw fasteners in steel-to-steel
connections is less than 3 times the nominal diameter but greater than or equal
to 2 times the nominal diameter, screw fasteners shall be considered 80
percent effective.
B1.5.1.4 Gypsum Board
Screw fasteners for gypsum board to steel connections shall be bugle head style in
compliance with ASTM C954, ASTM C1002, or ASTM C1513, as applicable.
B1.5.2 Welded Connections
Welded connections shall be in accordance with AISI S100 [CSA S136] and AWS D1.3.
The design capacity of welds shall be in accordance with AISI S100 [CSA S136].
B1.5.3 Bolts
Bolted cold-formed steel connections shall be designed and installed in accordance with
AISI S100 [CSA S136].
B1.5.4 Power-Actuated Fasteners
Cold-formed steel connections using power-actuated fasteners shall be designed and
installed in accordance with AISI S100 [CSA S136].
B1.5.5 Other Connectors
Other types of connections (e.g., rivet fasteners and clinch joining) shall be designed,
fabricated and installed in accordance with the design requirements as set forth by the
approved construction documents and the fastener manufacturers requirements.

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North American Standard For Cold-Formed Steel Structural Framing, 2015 Edition

B1.5.6 Connection to Other Materials

Bolts, nails, anchor bolts or other fasteners used to connect cold-formed steel framing to
wood, masonry, concrete or other steel components shall be designed and installed in
accordance with the applicable building code or the approved construction documents.
B2 Floor and Ceiling Framing
The requirements in Section B2 shall be used in conjunction with the requirements in
Section B1, as applicable.
B2.1 Scope
Sections B2.2 through B2.7 are applicable to floor and ceiling systems that utilize cold-formed
steel structural members.
B2.2 Floor Joist Design
Floor joists shall be designed in accordance with the requirements of this section.
B2.2.1 Bending
The available bending strength [factored resistance] of floor joists shall be the lesser of the
strengths determined in accordance with Sections B2.2.1.1 and B2.2.1.2.
B2.2.1.1 Lateral-Torsional Buckling
Floor joists shall be designed either on the basis of discretely braced design or on the
basis of continuously braced design, in accordance with the following:
(a) Discretely Braced Design. For discretely braced design, flexure shall be evaluated in
accordance with Section C3.1.2 of AISI S100 [CSA S136].
(b) Continuously Braced Design. For continuously braced design, where structural
sheathing or steel deck is attached to the compression flange of the floor joist in
accordance with Section B2.6(1) and the tension flange is braced in accordance with
Section B2.6(2), flexure shall be evaluated in accordance with Section C3.1.1 of AISI
S100 [CSA S136].
B2.2.1.2 Distortional Buckling
Floor joists shall be designed either on the basis of discretely braced design or on the
basis of continuously braced design, in accordance with the following:
(a) Discretely Braced Design. For discretely braced design, flexure shall be evaluated in
accordance with Section C3.1.4 of AISI S100 [CSA S136]. If the discrete bracing
restricts rotation of the compression flange about the web/flange juncture, the distance
between braces shall be used as Lm when applying AISI S100 [CSA S136].
(b) Continuously Braced Design. For continuously braced design, flexure shall be
evaluated in accordance with Section C3.1.4 of AISI S100 [CSA S136]. The rotational
stiffness, k, provided by the sheathing or deck to the floor joist shall be determined
in accordance with Appendix 1.
B2.2.2 Shear
Shear shall be evaluated in accordance with Section C3.2 of AISI S100 [CSA S136].

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AISI S240-15

B2.2.3 Web Crippling

Web crippling shall be evaluated in accordance with Section C3.4 of AISI S100 [CSA
S136], unless a bearing stiffener is used in accordance with the requirements of Section
B2.5.1.
B2.2.4 Bending and Shear
The combination of flexure and shear shall be evaluated in accordance with Section
C3.3 of AISI S100 [CSA S136].
B2.2.5 Bending and Web Crippling
The combination of flexure and web crippling shall be evaluated in accordance with
Section C3.5 of AISI S100 [CSA S136], unless a bearing stiffener is used in accordance with
the requirements of Section B2.5.1.
B2.3 Ceiling Joist Design
Ceiling joists shall be designed in accordance with the requirements of this section.
B2.3.1 Tension
Tension shall be evaluated in accordance with Section C2 of AISI S100 [CSA S136].
B2.3.2 Compression
The available compression strength [factored resistance] of ceiling joists shall be the lesser
of the strengths determined in accordance with Sections B2.3.2.1 and B2.3.2.2.
B2.3.2.1 Yielding, Flexural, Flexural-Torsional and Torsional Buckling
Compression shall be evaluated in accordance with Section C4.1 of AISI S100 [CSA
S136].
B2.3.2.2 Distortional Buckling
Ceiling joists shall be designed either on the basis of discretely braced design or on
the basis of continuously braced design, in accordance with the following:
(a) Discretely Braced Design. For discretely braced design, compression shall be
evaluated in accordance with Section C4.2 of AISI S100 [CSA S136]. If the discrete
bracing restricts rotation of the compression flange about the web/flange juncture, the
distance between braces shall be used as Lm when applying AISI S100 [CSA S136].
(b) Continuously Braced Design. For continuously braced design, compression alone
shall be evaluated in accordance with Section C4.2 of AISI S100 [CSA S136]. The
rotational stiffness, k, provided by the sheathing or deck to the ceiling joist shall be
determined in accordance with Appendix 1.
B2.3.3 Bending
The available flexural strength [resistance] of ceiling joists shall be the lesser of the
strengths determined in accordance with Sections B2.3.3.1 and B2.3.3.2.
B2.3.3.1 Lateral-Torsional Buckling
Ceiling joists shall be designed either on the basis of discretely braced design or on
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North American Standard For Cold-Formed Steel Structural Framing, 2015 Edition

the basis of continuously braced design, in accordance with the following:

(a) Discretely Braced Design. For discretely braced design, flexure shall be evaluated in
accordance with Section C3.1.2 of AISI S100 [CSA S136].
(b) Continuously Braced Design. For continuously braced design, where structural
sheathing or steel deck is attached to the compression flange of the ceiling joist in
accordance with Section B2.6 (1) and the tension flange is braced in accordance with
Section B2.6(2), flexure for gravity loading shall be evaluated in accordance with
Section C3.1.1 of AISI S100 [CSA S136] and flexure for uplift loading shall be
evaluated in accordance with Sections C3.1.2 and D6.1.1 of AISI S100 [CSA S136].
B2.3.3.2 Distortional Buckling
Ceiling joists shall be designed either on the basis of discretely braced design or on
the basis of continuously braced design, in accordance with the following:
(a) Discretely Braced Design. For discretely braced design, flexure shall be evaluated in
accordance with Section C3.1.4 of AISI S100 [CSA S136]. If the discrete bracing
restricts rotation of the compression flange about the web/flange juncture, the distance
between braces shall be used as Lm when applying AISI S100 [CSA S136].
(b) Continuously Braced Design. For continuously braced design, flexure shall be
evaluated in accordance with Section C3.1.4 of AISI S100 [CSA S136]. The rotational
stiffness, k, provided by the sheathing or deck to the ceiling joist shall be determined
in accordance with Appendix 1.
B2.3.4 Shear
Shear shall be evaluated in accordance with Section C3.2 of AISI S100 [CSA S136].
B2.3.5 Web Crippling
Web crippling shall be evaluated in accordance with Section C3.4 of AISI S100 [CSA
S136], unless a bearing stiffener is used in accordance with the requirements of Section
B2.5.1.
B2.3.6 Axial Load and Bending
The combination of axial load and bending shall be evaluated in accordance with
Section C5 of AISI S100 [CSA S136].
B2.3.7 Bending and Shear
The combination of flexure and shear shall be evaluated in accordance with Section
C3.3 of AISI S100 [CSA S136].
B2.3.8 Bending and Web Crippling
The combination of flexure and web crippling shall be evaluated in accordance with
Section C3.5 of AISI S100 [CSA S136], unless a bearing stiffener is used in accordance with
the requirements of Section B2.5.1.
B2.4 Floor Truss Design
Floor trusses shall be designed in accordance with Chapter E.

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AISI S240-15

B2.5 Bearing Stiffeners

Bearing stiffeners, other than clip angle bearing stiffeners, shall be designed in accordance
with Section C3.7 of AISI S100 [CSA S136]. Clip angle bearing stiffeners, as permitted in Section
B2.2.3, shall be designed in accordance with Section B2.5.1.
B2.5.1 Clip Angle Bearing Stiffeners
The nominal web crippling strength [resistance] of a floor joist connected to a rim track
using a clip angle bearing stiffener shall be determined in accordance with the following:
Pn = 0.9 (Pj + Pt + 0.5AgFy)
(Eq. B2.5.1-1)
where
Pj = Nominal end two-flange web crippling strength [resistance] of the floor joist
determined in accordance with Section C3.4.1 of AISI S100 [CSA S136]
Pt = Nominal interior two-flange web crippling strength [resistance] of the rim track
determined in accordance with Section C3.4.1 of AISI S100 [CSA S136]
Ag = Gross area of the clip angle bearing stiffener
Fy = Yield strength of clip angle
The available strength [factored resistance] shall be determined using the safety factor ()
or the resistance factor () as follows:
c = 1.80 for ASD
c = 0.85 for LRFD
c = 0.70 for LSD
Equation B2.5.1-1 shall be valid for the range of parameters listed in Table B2.5.1-1, as
illustrated in Figure B2.5-1.
Width of
Bearing
Stiffener
1 (25.4 mm)
(maximum)
Depth of
Bearing
Stiffener
1 (25.4 mm)
(maximum)
Three (3) Equally Spaced Screws
Figure B2.5-1 Fastening of Clip Angle Bearing Stiffener

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North American Standard For Cold-Formed Steel Structural Framing, 2015 Edition

Table B2.5.1-1
Parameters for Equation B2.5.1-1
Parameter

Minimum

Maximum

0.0451 (1.146 mm)

0.1017 (2.583 mm)

Design Yield Strength

33 ksi (228 MPa)

50 ksi (345 MPa)

Nominal Depth of Joist

8 (203 mm)

12 (305 mm)

1 (38.1 mm)

n/a

1x 1 (38.1 mm x 38.1 mm)

0.0312 (0.792 mm)

0.0713 (1.811 mm)

33 ksi (228 MPa)

50 ksi (345 MPa)

Joist depth minus 3/8 (9.5 mm)

n/a

Floor Joist and Rim Track:

Design Thickness

Bearing Width
Clip Angle Bearing Stiffener:
Size
Design Thickness
Design Yield Strength
Length
Installation:

No. 8 for angle design thickness

less than or equal to 0.0566

Screw Size

(1.438 mm), and

n/a

No. 10 for thicker angles

3 screws connecting legs of
bearing stiffener to joist and rim
track web, in accordance with
Figure B2.5-1

Fasteners

n/a

B2.6 Bracing Design

Bracing members shall be designed either on the basis of discretely braced design or on
the basis of continuously braced design, in accordance with the following:
(a) Discretely Braced Design. For discretely braced design, bracing members shall be
designed in accordance with Section D3 of AISI S100 [CSA S136].
(b) Continuously Braced Design. For continuously braced design, bracing members shall be
designed in accordance with Section D3 of AISI S100 [CSA S136], unless the following
requirements, as applicable, are met:
(1) The sheathing or deck shall consist of a minimum of 3/8 inch (9.5 mm) wood
structural sheathing that complies with DOC PS 1, DOC PS 2, CSA O437 or CSA O325,
or steel deck with a minimum profile depth of 9/16 in. (14.3 mm) and a minimum
thickness of 0.0269 in. (0.683 mm). The sheathing or deck shall be attached with
minimum No. 8 screws at a maximum 12 inches (305 mm) on center.
(2) Floor joists and ceiling joists with simple or continuous spans that exceed 8 feet (2.44
m) shall have the tension flanges laterally braced. Each intermediate brace shall be
spaced at 8 feet (2.44 m) maximum and shall be designed to resist a required lateral
force, PL, determined in accordance with the following:
For uniform loads:
PL = 1.5(m/d) F
where
m = Distance from shear center to mid-plane of web
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(Eq. B2.6-1)

AISI S240-15

d = Depth of C-shape section

F = wa
w = Uniform design load [factored load]
a = Distance between center line of braces
For concentrated loads:
If x 0.3a:
PL = 1.0(m/d) F
If 0.3a < x < 1.0a:
PL = 1.4(m/d)(1-x/a) F
where
m = Distance from shear center to mid-plane of web
d = Depth of C-shape section
F = Concentrated design load [factored load]
x = Distance from concentrated load to brace
a = Distance between center line of braces

(Eq. B2.6-2)
(Eq. B2.6-3)

B2.7 Floor Diaphragm Design

Diaphragms shall be designed in accordance with Section B5.
B3 Wall Framing
The requirements in Section B3 shall be used in conjunction with the requirements in
Section B1, as applicable.
B3.1 Scope
Sections B3.2 through B3.5 are applicable to wall systems that utilize cold-formed steel
structural members.
B3.2 Wall Stud Design
Wall studs shall be designed in accordance with the requirements of this section.
B3.2.1 Available Axial Strength [Factored Resistance]
The available axial strength [factored resistance] of wall stud shall be the lesser of the
available strengths [factored resistance] obtained by Sections B3.2.1.1 and B3.2.1.2.
B3.2.1.1 Yielding, Flexural, Flexural-Torsional and Torsional Buckling
Wall studs shall be designed either on the basis of all steel design or on the basis of
sheathing braced design with both ends of the stud connected to restrain rotation about
the longitudinal stud axis and horizontal displacement perpendicular to the stud axis, in
accordance with the following:
(a) All Steel Design. For all steel design of wall studs in compression, Sections C4.1 and
D4.1 of AISI S100 [CSA S136] shall define the available axial strength [factored
resistance]. The effective length, KL, shall be determined by rational engineering
analysis or testing, or in the absence of such analysis or tests, Kx, Ky and Kt shall be
taken as unity. The unbraced length with respect to the major axis, Lx, shall be taken
as the distance between end supports of the member, while unbraced lengths Ly and
Lt shall be taken as the distance between braces.

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North American Standard For Cold-Formed Steel Structural Framing, 2015 Edition

(b) Sheathing Braced Design. For sheathing braced design of wall studs in compression,
the available axial strength [factored resistance] shall be determined in accordance with
Section C4.1 of AISI S100 [CSA S136]. The unbraced length with respect to the major
axis, Lx, shall be taken as the distance between end supports of the member. The
unbraced length with respect to the minor axis, Ly, and the unbraced length for
torsion, Lt, shall be taken as twice the distance between sheathing connectors. The
buckling coefficients Kx, Ky, and Kt shall be taken as unity.
To prevent failure of the sheathing-to-wall stud connection, where identical gypsum
sheathing is attached to both sides of the wall stud with screws spaced at a maximum
of 12 inches (305 mm) on center, the maximum axial nominal load [specified load] in the
wall stud shall be limited to the values given in Table B3.2-1.
Table B3.2-1
Maximum Axial Nominal Load [Specified Load]
Limited by Gypsum Sheathing-to-Wall Stud Connection Capacity
Maximum Nominal [Specified]
Gypsum Sheathing
Screw Size
Stud Axial Load
1/2 inch (12.7 mm)
1/2 inch (12.7 mm)
5/8 inch (15.9 mm)
5/8 inch (15.9 mm)

No. 6
No. 8
No. 6
No. 8

5.8 kips (25.8 kN)

6.7 kips (29.8 kN)
6.8 kips (30.2 kN)
7.8 kips (34.7 kN)

B3.2.1.2 Distortional Buckling

Wall studs shall be designed either on the basis of all steel design or on the basis of
sheathing braced design, in accordance with the following:
(a) All Steel Design. For all steel design, compression shall be evaluated in accordance
with Section C4.2 of AISI S100 [CSA S136]. If the discrete bracing restricts rotation of
both flanges about the web/flange juncture, the distance between braces shall be used
as Lm when applying AISI S100 [CSA S136].
(b) Sheathing Braced Design. For sheathing braced design, compression shall be
evaluated in accordance with Section C4.2 of AISI S100 [CSA S136]. The rotational
stiffness, k, provided by the sheathing or deck to the wall stud shall be determined
in accordance with Appendix 1.
B3.2.2 Bending
The available flexural strength [factored resistance] of wall stud shall be the lesser of the
strengths [resistance] obtained by Sections B3.2.2.1 and B3.2.2.2.
B3.2.2.1 Lateral-Torsional Buckling
Wall studs shall be designed either on the basis of all steel design or on the basis of
sheathing braced design, in accordance with the following:
(a) All Steel Design. For all steel design, Section C3.1.2 of AISI S100 [CSA S136] shall
define the available flexural strength [factored resistance].
(b) Sheathing Braced Design. For sheathing braced design, and assuming full rotational
restraint provided by the sheathing, Section C3.1.1 of AISI S100 [CSA S136] shall
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AISI S240-15

define the available flexural strength [factored resistance].

B3.2.2.2 Distortional Buckling
Wall studs shall be designed either on the basis of all steel design or on the basis of
sheathing braced design, in accordance with the following:
(a) All Steel Design. For all steel design, flexure shall be evaluated in accordance with
Section C3.1.4 of AISI S100 [CSA S136]. If the discrete bracing restricts rotation of the
compression flange about the web/flange juncture, the distance between braces shall
be used as Lm when applying AISI S100 [CSA S136].
(b) Sheathing Braced Design. For sheathing braced design, flexure shall be evaluated in
accordance with Section C3.1.4 of AISI S100 [CSA S136]. The rotational stiffness, k,
provided by the sheathing or deck to the compression flange of the wall stud shall be
determined in accordance with Appendix 1.
B3.2.3 Shear
The available shear strength [factored resistance] shall be determined in accordance with
Section C3.2 of AISI S100 [CSA S136].
B3.2.4 Axial Load and Bending
The combination of axial load and bending shall be evaluated in accordance with
Section C5 of AISI S100 [CSA S136].
B3.2.5 Web Crippling
The available web crippling strength [factored resistance] shall be determined in
accordance with Section C3.4 of AISI S100 [CSA S136], or shall be determined in
accordance with Section B3.2.5.1 for C-section stud-to-track connections and Section B3.2.5.2
for C-section stud-to-deflection track connections.
B3.2.5.1 Stud-to-Track Connection for C-Section Studs
The available web crippling strength [factored resistance] of C-Section stud-to-track
connections are permitted to be determined in accordance with Items (a) to (c), as
applicable:
(a) For single curtain wall studs where both stud flanges are connected to the track flanges,
the nominal strength [resistance], Pnst, shall be determined in accordance with Eq.
B3.2.5.1-1. For members consisting of two studs, Pnst is the sum of the individual stud
web capacities with the stud design thickness, t, taken as the thickness of one web.

R
N
h

1 + C N
1 C h
Pnst = Ct 2 Fy 1 C R

t
t
t

where
C = Web crippling coefficient listed in Table B3.2.5.1-1
CR = Inside bend radius coefficient
= 0.19
CN = Bearing length coefficient
= 0.74

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(Eq. B3.2.5.1-1)

North American Standard For Cold-Formed Steel Structural Framing, 2015 Edition

Ch = Web slenderness coefficient

= 0.019
R
= Stud inside bend radius
N = Stud bearing length
= 1.25 inch (32 mm)
h
= Depth of flat portion of stud web measured along plane of web
t
= Stud design thickness
The available strength [factored resistance] shall be determined using the safety factor ()
or the resistance factor () as follows:
= 1.70 for ASD for single stud interior configuration
= 1.90 for ASD for all other configurations listed in Table B3.2.5.1-1

= 0.90 for LRFD for single stud interior configuration

= 0.85 for LRFD for all other configurations listed in Table B3.2.5.1-1
= 0.75 for LSD for single stud interior configuration
= 0.70 for LSD for all other configurations listed in Table B3.2.5.1-1
Equation B3.2.5.1-1 shall be valid for the range of parameters listed in Table B3.2.5.1-2.
Table B3.2.5.1-1
Web Crippling Coefficients
Configuration

Location

Web Crippling Coefficient, C

Single stud

Interior

3.70

Single stud with

reinforcing lips facing
opening

At a wall opening

2.78

Single stud with stud

web facing opening

At a wall opening

1.85

Toe-to-toe
double studs

Interior

7.40

Toe-to-toe
double studs

At an opening

5.55

Back-to-back
double studs

Interior

7.40

Back-to-back
double studs

At an opening

7.40

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AISI S240-15

Table B3.2.5.1-2
Parameters for Equation B3.2.5.1-1
Parameter

Minimum

Maximum

No. 8 for 0.0451 in. (1.146 mm) and

thinner stud design thickness
No. 10 for 0.0452 to 0.0566 in. (1.147
to 1.438 mm) stud design thickness

Screw Size

n/a

No. 12 for 0.0567 in. ( 1.439 mm) and

thicker stud design thickness
Stud Section:
Design Thickness
Design Yield Strength
Nominal Depth

0.0346 inch (0.88 mm)

0.0770 inch (1.96 mm)

33 ksi (228 MPa)

50 ksi (345 MPa)

3.50 inch (88.9 mm)

6.0 inch (152.4 mm)

0.0346 inch (0.88 mm)

0.0770 inch (1.96 mm)

33 ksi (228 MPa)

50 ksi (345 MPa)

Track Section:
Design Thickness
Design Yield Strength
Nominal Depth

3.50 inch (88.9 mm)

6.0 inch (152.4 mm)

Nominal Flange Width

1.25 inch (31.8 mm)

2.375 inch (60.3 mm)

(b) For single curtain wall studs that are not adjacent to wall openings and where both
stud flanges are connected to the track flanges and the track thickness is less than the
stud thickness, the nominal strength [resistance], Pnst, shall be the lesser value
determined in accordance with Equation B3.2.5.1-1 or B3.2.5.1-2.
(Eq. B3.2.5.1-2)
Pnst = 0.6 tt wst Fut
where:
= Track design thickness
tt
wst = 20 tt + 0.56

= Coefficient for conversion of units

= 1.0 when tt is in inches
= 25.4 when tt is in mm
Fut = Tensile strength of the track
Pnst = Nominal strength [resistance] for the stud-to-track connection when subjected
to transverse loads
The available strength [factored resistance] shall be determined using the safety factor ()
or the resistance factor () as follows:
= 1.70 for ASD

= 0.90 for LRFD

= 0.80 for LSD
Equation B3.2.5.1-2 shall be valid for the range of parameters listed in
Table B3.2.5.1-3.

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North American Standard For Cold-Formed Steel Structural Framing, 2015 Edition

Table B3.2.5.1-3
Parameters for Equation B3.2.5.1-2
Parameter

Minimum

Maximum

No. 8

n/a

0.0346 inch (0.88 mm)

0.0770 inch (1.96 mm)

33 ksi (228 MPa)

50 ksi (345 MPa)

3.50 inch (88.9 mm)

6.0 inch (152.4 mm)

0.0346 inch (0.88 mm)

0.0770 inch (1.96 mm)

33 ksi (228 MPa)

50 ksi (345 MPa)

Nominal Depth

3.50 inch (88.9 mm)

6.0 inch (152.4 mm)

Nominal Flange Width

1.25 inch (31.8 mm)

2.375 inch (60.3 mm)

Screw Size
Stud Section:
Design Thickness
Design Yield Strength
Nominal Depth
Track Section:
Design Thickness
Design Yield Strength

(c) For curtain wall jamb studs made up of two studs connected back-to-back where both
stud flanges are connected to the track flanges and the track thickness is the same as the
stud thickness, the nominal strength [resistance], Pnst, is the lesser value determined in
accordance with Equation B3.2.5.1-1 or B3.2.5.1-3.
(Eq. B3.2.5.1-3)
Pnst = 15.2 tt2 Fut
where
tt = Track design thickness
Fut = Tensile strength of the track
The available strength [factored resistance] shall be determined using the safety factor ()
or the resistance factor () as follows:
= 2.10 for ASD
= 0.75 for LRFD
= 0.65 for LSD
Equation B3.2.5.1-3 shall be valid for the range of parameters listed in
Table B3.2.5.1-4.
Table B3.2.5.1-4
Parameters for Equation B3.2.5.1-3
Parameter

Minimum

Maximum

No. 10

n/a

0.0346 inch (0.88 mm)

0.0770 inch (1.96 mm)

33 ksi (228 MPa)

50 ksi (345 MPa)

3.50 inch (88.9 mm)

6.0 inch (152.4 mm)

0.0346 inch (0.88 mm)

0.0770 inch (1.96 mm)

33 ksi (228 MPa)

50 ksi (345 MPa)

Nominal Depth

3.50 inch (88.9 mm)

6.0 inch (152.4 mm)

Nominal Flange Width

1.25 inch (31.8 mm)

Screw Size
Stud Section:
Design Thickness
Design Yield Strength
Nominal Depth
Track Section:
Design Thickness
Design Yield Strength

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AISI S240-15

(d) For curtain wall studs that are not adjacent to wall openings and do not have both
stud flanges connected to the track flanges and the track thickness is greater than or
equal to the stud thickness, nominal strength [resistance], Pnst shall equal Pn, along
with and , as determined by Section C3.4.1 of AISI S100 [CSA S136]. For two studs
connected back-to-back, the two members shall be considered individually as single
web members.
(e) For curtain wall studs that are adjacent to wall openings and do not have both stud
flanges connected to the track flanges and the track thickness is greater than or equal to
the stud thickness, nominal strength [resistance], Pnst shall equal 0.5Pn, along with
and , as determined by Section C3.4.1 of AISI S100 [CSA S136]. For two studs
connected back-to-back, the two members shall be considered individually as single
web members.
B3.2.5.2 Deflection Track Connection for C-Section Studs
B3.2.5.2.1 For curtain wall studs used in deflection track connections, the nominal web
crippling strength [resistance], Pnst and the and factors shall be determined by
Section C3.4.1 of AISI S100 [CSA S136]. The bearing length used in these
calculations shall not exceed the minimum engagement between the stud and the
track or 1 inch (25.4 mm).
B3.2.5.2.2 The nominal strength [resistance] of a single deflection track subjected to
transverse loads and connected to its support at a fastener spacing not greater than
the stud spacing shall be determined in accordance with Eq. B3.2.5.2-1.
Pndt =

w dt t t 2 Fy

where
wdt =
=
S
=
=
tt
Fy =
e
=

(Eq. B3.2.5.2-1)

Effective track length

0.11(2)(e0.5/tt1.5) + 5.5 S
(Eq. B3.2.5.2-2)
Center-to-center spacing of studs
Track design thickness
Design yield strength of track material
Design end or slip gap (distance between stud web at end of stud and
track web)

= Coefficient for conversion of units

= 1.0 when e, tt and S are in inches
= 25.4 when e, tt and S are in mm
The available strength [factored resistance] shall be determined using the safety factor
() or the resistance factor () as follows:
= 2.80 for ASD

= 0.55 for LRFD

= 0.45 for LSD
Equation B3.2.5.2-1 shall be valid for the range of parameters listed in Table
B3.2.5.2-1. Additionally, the horizontal distance from the web side of the stud to the
terminating end of the track shall not be less than one-half the effective track length
wdt.

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North American Standard For Cold-Formed Steel Structural Framing, 2015 Edition

Table B3.2.5.2-1
Parameters for Equation B3.2.5.2-1
Parameter

Minimum

Maximum

No. 10

n/a

0.0451 inch (1.14 mm)

0.0713 inch (1.81 mm)

33 ksi (228 MPa)

50 ksi (345 MPa)

3.50 inch (88.9 mm)

6.0 inch (152.4 mm)

Screw Size
Stud Section:
Design Thickness
Design Yield Strength
Nominal Depth

1.625 inch (41.3 mm)

2.50 inch (63.5 mm)

Stud Spacing

Nominal Flange Width

12 inch (305 mm)

24 inch (610 mm)

Stud Bearing Length

inch (19.1 mm)

n/a

0.0451 inch (1.14 mm)

0.0713 inch (1.81 mm)

33 ksi (228 MPa)

50 ksi (345 MPa)

Nominal Depth

3.50 inch (88.9 mm)

6.0 inch (152.4 mm)

Nominal Flange Width

2.00 inch (50.8 mm)

3.00 inch (76.3 mm)

Track Section:
Design Thickness
Design Yield Strength

B3.3 Header Design

B3.3.1 Back-to-Back Headers
The requirements of this section shall be limited to back-to-back header beams that are
installed using cold-formed steel C-shape sections in accordance with Section C3.4.4.
B3.3.1.1 Bending
Bending shall be evaluated in accordance with Section C3.1.1 of AISI S100 [CSA
S136].
B3.3.1.2 Shear
Shear shall be evaluated in accordance with Section C3.2 of AISI S100 [CSA S136].
B3.3.1.3 Web Crippling
Web crippling shall be evaluated in accordance with Section C3.4 of AISI S100 [CSA
S136]. For back-to-back header beams, the coefficients for built-up sections in Table
C3.4.1-1 of AISI S100 [CSA S136] shall be used.
B3.3.1.4 Bending and Shear
The combination of bending and shear shall be evaluated in accordance with Section
C3.3 of AISI S100 [CSA S136].
B3.3.1.5 Bending and Web Crippling
Webs of back-to-back header beams subjected to a combination of bending and web
crippling shall be designed in accordance with Section C3.5 of AISI S100 [CSA S136]. For
back-to-back header beams, AISI S100 [CSA S360] Sections C3.5.1 (b) for ASD and
C3.5.2 (b) for LRFD and LSD shall be used.
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AISI S240-15

B3.3.2 Box Headers

The requirements of this section shall be limited to box header beams that are installed
using cold-formed steel C-shape sections in accordance with Section C3.4.4.
B3.3.2.1 Bending
Bending shall be evaluated in accordance with Section C3.1.1 of AISI S100 [CSA
S136].
B3.3.2.2 Shear
Shear shall be evaluated in accordance with Section C3.2 of AISI S100 [CSA S136].
B3.3.2.3 Web Crippling
Web crippling shall be evaluated in accordance with Section C3.4 of AISI S100 [CSA
S136]. For box header beams, the equations for shapes having single webs shall be used.
The nominal web crippling strength [resistance], Pn, for an interior one-flange loading
condition, with the applicable or factor specified below, is permitted to be
multiplied by , where accounts for the increased strength due to the track and is
specified as follows:
= Parameter determined in accordance with equation B3.3.2.3-1 or B3.3.2.3-2
The available strength [factored resistance] shall be determined using the safety factor ()
or the resistance factor () as follows:
= 1.80 for ASD
= 0.85 for LRFD
= 0.80 for LSD
Where the track section design thickness 0.0346 in. (0.879 mm), the track flange width
1 in. (25.4 mm), the C-shape section depth 12 in. (305 mm) and the C-shape section
design thickness 0.0346 in. (0.879 mm):
t
(Eq. B3.3.2.3-1)
=
2.3 t 1.0
tc
where
tt = 0.0346 in. (0.879 mm)
tc = Design thickness of the C-shape section
Where the limits of Equation B3.3.2.3-1 are not met:
=1.0

(Eq. B3.3.2.3-2)

B3.3.2.4 Bending and Shear

The combination of bending and shear shall be evaluated in accordance with Section
C3.3 of AISI S100 [CSA S136].
B3.3.2.5 Bending and Web Crippling
Webs of box header beams subjected to a combination of bending and web crippling
shall be determined in accordance with either Section C3.5 of AISI S100 [CSA S136] or
the following equations:

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North American Standard For Cold-Formed Steel Structural Framing, 2015 Edition

(a) For ASD:

P
M
1.5
+

Pn M n

(Eq. B3.3.2.5-1)

where
P = Required web crippling strength
M = Required flexural strength
Pn = Nominal web crippling strength determined in accordance with Section
B3.3.2.3
Mn = Nominal flexural strength defined in Section C3.1 of AISI S100 [CSA S136]
The available strength [factored resistance] shall be determined using the safety factor ()
as follows:
= 1.85

(b) For LRFD and LSD:

Pu M u
+
1.5
Pn M n

(Eq. B3.3.2.5-2)
where
Pu = Required web crippling strength [compression force due to factored loads]
Mu = Required flexural strength [moment due to factored loads]
Pn = Nominal web crippling strength [resistance] computed by Section
B3.3.2.3
Mn = Nominal flexural strength [resistance] defined in Section C3.1 of AISI S100
[CSA S136]
The available strength [factored resistance] shall be determined using the resistance factor
() as follows:
= 0.85 for LRFD
= 0.80 for LSD

B3.3.3 Double L-Headers

The requirements of this section shall be limited to double L-headers that are installed
using two cold-formed steel angles in accordance with Section C3.4.5 and meet all of the
following conditions:
(a) Minimum top flange width = 1.5 inches (38.1 mm)
(b) Maximum vertical leg dimension = 10 inches (254 mm)
(c) Minimum base steel thickness = 0.033 inches (0.838 mm)
(d) Maximum design thickness = 0.0713 inches (1.829 mm)
(e) Minimum design yield strength, Fy = 33 ksi (230 MPa)
(f) Maximum design yield strength, Fy = 50 ksi (345 MPa)
(g)
(h)
(i)
(j)

Cripple stud located at all load points

Minimum bearing length 1.5 inches (38.1 mm) at load points
Minimum wall width = 3.5 inches (88.9 mm)
Maximum span = 16 ft.-0 in. (4.88 m)

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AISI S240-15

B3.3.3.1 Bending
The available flexural strength [factored resistance] of double L-headers shall be
determined in accordance with this section.
B3.3.3.1.1 Gravity Loading
The gravity nominal flexural strength [moment resistance], Mng, shall be determined as
follows:
when L/Lh 10
(Eq. B3.3.3.1.1-1)
Mng = Sec Fy
when L/Lh < 10 and Lh > 8 in. (203 mm) (Eq. B3.3.3.1.1-2)
= 0.9 Sec Fy
The available strength [factored resistance] shall be determined using the safety factor
() or the resistance factor () as follows:
For Lh 8 in. (203 mm):
= 1.67 (ASD)
= 0.90 (LRFD)
= 0.85 (LSD)
For Lh > 8 in. (203 mm):
= 2.25 (ASD)
= 0.70 (LRFD)
= 0.65 (LSD)
where
Fy = Yield strength used for design
Sec = Elastic section modulus of the effective section calculated at f = Fy in the
extreme compression fibers
L = Span length
Lh = Vertical leg dimension of angle
B3.3.3.1.2 Uplift Loading
The nominal uplift flexural strength [moment resistance], Mnu, shall be determined
as follows:
(Eq. B3.3.3.1.2-1)
Mnu = R Mng
The available strength [factored resistance] shall be determined using the safety factor
() or the resistance factor () as follows:
= 2.0 (ASD)

= 0.80 (LRFD)
= 0.75 (LSD)
where
Mng = Gravity nominal flexural strength [moment resistance] determined by Eq.
B3.3.3.1.2-1
R
= Uplift factor
= 0.25 for Lh/t 150
= 0.20 for Lh/t 170
= For 150 < Lh/t < 170 use linear interpolation
Lh = Vertical leg dimension of the angle
= Design thickness
t
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North American Standard For Cold-Formed Steel Structural Framing, 2015 Edition

B3.3.3.2 Shear
Shear need not be evaluated for the design of double L-header beams that are
fabricated and installed in accordance with this Standard.
B3.3.3.3 Web Crippling
Web crippling need not be evaluated for the design of double L-header beams that
are fabricated and installed in accordance with this Standard.
B3.3.3.4 Bending and Shear
The combination of bending and shear need not be evaluated for the design of
double L-header beams fabricated and installed in accordance with this Standard.
B3.3.3.5 Bending and Web Crippling
The combination of bending and web crippling need not be evaluated for the design
of double L-header beams fabricated and installed in accordance with this Standard.
B3.3.4 Single L-Headers
The requirements of this section shall be limited to single L-headers that are installed
using one cold-formed steel angle in accordance with Section C3.4.5 and meet all of the
following conditions:
(a) Minimum top flange width = 1.5 inches (38.1 mm)
(b) Maximum vertical leg dimension = 8 inches (203 mm)
(c) Minimum base steel thickness = 0.033 inches (0.838 mm)
(d) Maximum design thickness = 0.0566 inches (1.448 mm)
(e) Minimum design yield strength, Fy = 33 ksi (230 MPa)
(f) Maximum design yield strength, Fy = 50 ksi (345 MPa)
(g)
(h)
(i)
(j)

Cripple stud located at all load points

Minimum bearing length 1.5 inches (38.1 mm) at load points
Minimum wall width = 3.5 inches (88.9 mm)
Maximum span = 4-0 (1.219 m)

B3.3.4.1 Bending
The available flexural strength [factored resistance] of single L-headers shall be
determined in accordance with this section.
B3.3.4.1.1 Gravity Loading
The gravity nominal flexural strength [resistance], Mng, shall be determined as
follows:
when Lh 6 in. (152 mm)
(Eq. B3.3.4.1.1-1)
Mng = Sec Fy
= 0.9 Sec Fy
when 6 in. (152 mm) < Lh 8 in. (203 mm) (Eq. B3.3.4.1.1-1)
The available strength [factored resistance] shall be determined using the safety factor
() or the resistance factor () as follows:
= 1.67 (ASD)

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AISI S240-15

= 0.90 (LRFD)
= 0.85 (LSD)
where
Fy = Yield strength used for design
Sec = Elastic section modulus of the effective section calculated at f = Fy in the
extreme compression fibers

B3.3.4.1.2 Uplift Loading

[Reserved]
B3.3.4.2 Shear
Shear need not be evaluated for the design of single L-header beams that are
fabricated and installed in accordance with this Standard.
B3.3.4.3 Web Crippling
Web crippling need not be evaluated for the design of single L-header beams that are
fabricated and installed in accordance with this Standard.
B3.3.4.4 Bending and Shear
The combination of bending and shear need not be evaluated for the design of single
L-header beams fabricated and installed in accordance with this Standard.
B3.3.4.5 Bending and Web Crippling
The combination of bending and web crippling need not be evaluated for the design
of single L-header beams fabricated and installed in accordance with this Standard.
B3.3.5 Inverted L-Header Assemblies
B3.3.5.1 The requirements of this section shall be limited to inverted double or single
L-header assemblies satisfying the limitations specified in Section B3.3.3 for double
L-headers and B3.3.4 for single L-headers, respectively. The installation of inverted
L-header assemblies shall be in accordance with C3.4.6.
B3.3.5.2 For double inverted L-header assemblies, the nominal flexural strength [moment
resistance] of the combined L-header assembly (i.e., double L-headers plus inverted
double L-headers) shall be determined by summing the gravity and uplift nominal
flexural strengths [moment resistances] as determined in accordance with Section
B3.3.3.1.
B3.3.5.3 For single inverted L-header assemblies, the nominal flexural strength [moment
resistance] of the combined L-header assembly (i.e., a single L-header plus an inverted
single L-header) shall be based on the gravity nominal flexural strength [moment
resistance] as determined in accordance with Section B3.3.4.1.
B3.3.5.4 Shear, web crippling, bending and shear, and bending and web crippling need
not be evaluated for the design of inverted L-headers fabricated and installed in
accordance with this Standard.

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North American Standard For Cold-Formed Steel Structural Framing, 2015 Edition

B3.4 Bracing
B3.4.1 Intermediate Brace Design
B3.4.1.1 For bending members, each intermediate brace shall be designed in accordance
with Section D3.2.1 of AISI S100 [CSA S136].
B3.4.1.2 For axial loaded members, each intermediate brace shall be designed for 2% of
the design compression force in the member.
B3.4.1.3 For combined bending and axial loads, each intermediate brace shall be
designed for the combined brace force determined in accordance with Section D3.2.1
of AISI S100 [CSA S136] and 2% of the design compression force in the member.
B3.5 Serviceability
Serviceability limits shall be chosen based on the intended function of the wall system,
and shall be evaluated using load and load combinations in accordance with Section B1.1.
B4 Roof Framing
The requirements in Section B4 shall be used in conjunction with the requirements in
Section B1, as applicable.
B4.1 Scope
Sections B4.2 through B4.6 are applicable to roof systems that utilize cold-formed steel
structural members.
B4.2 Roof Rafter Design
Roof rafters shall be designed in accordance with the requirements of this section.
B4.2.1 Tension
Tension shall be evaluated in accordance with Section C2 of AISI S100 [CSA S136].
B4.2.2 Compression
The available compression strength [resistance] of roof rafters shall be the lesser values
obtained from Sections B4.2.2.1 and B4.2.2.2.
B4.2.2.1 Yielding, Flexural, Flexural-Torsional and Torsional Buckling
Compression shall be evaluated in accordance with Section C4.1 of AISI S100 [CSA
S136].
B4.2.2.2 Distortional Buckling
Roof rafters shall be designed either on the basis of discretely braced design or on the
basis of continuously braced design, in accordance with the following:
(a) Discretely Braced Design. For discretely braced design, compression shall be
evaluated in accordance with Section C4.2 of AISI S100 [CSA S136]. If the discrete
bracing restricts rotation of the compression flange about the web/flange juncture, the
distance between braces shall be used as Lm when applying AISI S100 [CSA S136].
(b) Continuously Braced Design. For continuously braced design, compression shall be
evaluated in accordance with Section C4.2 of AISI S100 [CSA S136]. The rotational
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AISI S240-15

stiffness, k, provided by the sheathing or deck to the roof rafter shall be determined
in accordance with Appendix 1.
B4.2.3 Bending
The available flexural strength [resistance] of roof rafters shall be the lesser values obtained
from Sections B4.2.3.1 and B4.2.3.2.
B4.2.3.1 Lateral-Torsional Buckling
Roof rafters shall be designed either on the basis of discretely braced design or on the
basis of continuously braced design, in accordance with the following:
(a) Discretely Braced Design. For discretely braced design, flexure shall be evaluated in
accordance with Section C3.1.2 of AISI S100 [CSA S136].
(b) Continuously Braced Design. For continuously braced design, where structural
sheathing or steel deck is attached to the compression flange of the roof rafter in
accordance with Section B4.5(1) and the tension flange is braced in accordance with
Section B4.5(2), flexure for gravity loading shall be evaluated by using Section C3.1.1
of AISI S100 [CSA S136] and flexure for uplift loading shall be evaluated in
accordance with Sections C3.1.2 and D6.1.1 of AISI S100 [CSA S136]. Where structural
sheathing or steel deck is attached to both flanges of the roof rafter in accordance with
Section B4.5(1), flexure for gravity or uplift loading shall be evaluated in accordance
with Section C3.1.1 of AISI S100 [CSA S136].
B4.2.3.2 Distortional Buckling
Roof rafters shall be designed either on the basis of discretely braced design or on the
basis of continuously braced design, in accordance with the following:
(a) Discretely Braced Design. For discretely braced design, flexure alone shall be
evaluated in accordance with Section C3.1.4 of AISI S100 [CSA S136]. If the discrete
bracing restricts rotation of the compression flange about the web/flange juncture, the
distance between braces shall be used as Lm when applying AISI S100 [CSA S136].
(b) Continuously Braced Design. For continuously braced design, flexure shall be
evaluated in accordance with Section C3.1.4 of AISI S100 [CSA S136]. The rotational
stiffness, k, provided by the sheathing or deck to the roof rafter shall be determined
in accordance with Appendix 1.
B4.2.4 Shear
Shear shall be evaluated in accordance with Section C3.2 of AISI S100 [CSA S136].
B4.2.5 Web Crippling
Web crippling shall be evaluated in accordance with Section C3.4 of AISI S100 [CSA
S136], unless a bearing stiffener is used in accordance with the requirements of Section B4.4.
B4.2.6 Axial Load and Bending
The combination of axial load and bending shall be evaluated in accordance with
Section C5 of AISI S100 [CSA S136].

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North American Standard For Cold-Formed Steel Structural Framing, 2015 Edition

B4.2.7 Bending and Shear

The combination of flexure and shear shall be evaluated in accordance with Section
C3.3 of AISI S100 [CSA S136].
B4.2.8 Bending and Web Crippling
The combination of flexure and web crippling shall be evaluated in accordance with
Section C3.5 of AISI S100 [CSA S136], unless a bearing stiffener is used in accordance with
the requirements of Section B4.4.
B4.3 Roof Truss Design
Roof trusses shall be designed in accordance with Chapter E.
B4.4 Bearing Stiffeners
Bearing stiffeners shall be designed in accordance with Section C3.7 of AISI S100 [CSA
S136].
B4.5 Bracing Design
Bracing members shall be designed in accordance with Section D3 of AISI S100 [CSA
S136], unless bracing is provided satisfying the following requirements:
(a) In continuously braced design, the sheathing or deck shall consist of a minimum of 3/8
inch (9.5 mm) wood structural sheathing that complies with DOC PS 1, DOC PS 2, CSA
O437 or CSA O325, or steel deck with a minimum profile depth of 9/16 in. (14.3 mm) and
a minimum thickness of 0.0269 in. (0.683 mm). The sheathing or deck shall be attached
with minimum No. 8 screws at a maximum 12 inches (305 mm) on center.
(b) In continuously braced design, roof rafters with simple or continuous spans that exceed 8
feet (2.44 m) shall have the tension flanges laterally braced. Each intermediate brace shall
be spaced at 8 feet (2.44 m) maximum and shall be designed to resist a required lateral
force, PL, determined in accordance with the following:
(1) For uniform loads:
PL = 1.5(m/d) F
where
m = Distance from shear center to mid-plane of web
d = Depth of C-shape section
F = wa
w = Uniform design load [factored load]
a = Distance between center line of braces
(2) For concentrated loads:
If x 0.3a
PL = 1.0(m/d) F
If 0.3a < x < 1.0a
PL = 1.4(m/d)(1-x/a) F
where
m = Distance from shear center to mid-plane of web
d = Depth of C-shape section
F = Concentrated design load [factored load]

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(Eq. B4.5-1)

(Eq. B4.5-2)
(Eq. B4.5-3)

AISI S240-15

x = Distance from concentrated load to brace

a = Distance between center line of braces
B4.6 Roof Diaphragm Design
Diaphragms shall be designed in accordance with Section B5.4.
B5 Lateral Force-Resisting Systems
The requirements in Section B5 shall be used in conjunction with the requirements in
Section B1, as applicable.
B5.1 Scope
Sections B5.2 through B5.5 are applicable to buildings that utilize cold-formed steel
structural members for lateral force-resisting system framing.
User Note:

See Section A1.3 for applicability of this section to cold-formed steel structural members
and connections in seismic force-resisting systems.
B5.2 Shear Wall Design
Shear walls shall be designed as either Type I shear walls or Type II shear walls in accordance
with the requirements of this section and shall be installed in accordance with the
requirements of Section C3.6.1.
User Note:
See Section A1.3 for applicability of this section to cold-formed steel structural members and
connections in seismic force-resisting systems.

B5.2.1 General
Type I shear walls shall be fully sheathed with steel sheet sheathing, wood structural panels,
gypsum board panels, or fiberboard panels with hold-downs at each end. Type I shear walls
sheathed with steel sheet sheathing or wood structural panels are permitted to have openings
where details are provided to account for force transfer around openings. Type I shear walls
shall conform to the additional requirements of Sections B5.2.1.1.
Type II shear walls shall be sheathed with steel sheet sheatthing or wood structural panels
with a Type II shear wall segment at each end. Openings are permitted to occur beyond the
ends of the Type II shear wall; however, the width of such openings shall not be included in
the length of the Type II shear wall. Type II shear walls shall conform to the additional
requirements of Section B5.2.1.2.
B5.2.1.1 Type I Shear Walls
Type I shear walls shall conform to the following requirements:
(a) The height-to-length aspect ratio (h/w) of a Type I shear wall does not exceed the
values in Tables B5.2.2.3-1 through B5.2.2.3-4.
(b) The length of a Type I shear wall is not less than 24 inches (610 mm).
(c) The height-to-length aspect ratio (hp/wp) of a wall pier in a Type I shear wall with
openings is limited to a maximum of 2:1, where the height of a wall pier (hp) is
defined as the height of the opening adjacent to the sheathed wall and the length of a
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North American Standard For Cold-Formed Steel Structural Framing, 2015 Edition

wall pier (wp) is the sheathed length of the wall pier adjacent to the opening.
(d) The length of a wall pier (wp) in a Type I shear wall with openings is not less than 24
inches (610 mm).
B5.2.1.2 Type II Shear Walls
(a)
(b)
(c)

(d)
(e)
(f)

Type II shear walls shall conform to the following requirements:

The height-to-length aspect ratio (h/w) of a Type II shear wall segment does not exceed
the values in Tables B5.2.2.3-1 through B5.2.2.3-2.
For a Type II shear wall, the nominal strength [resistance] for shear, Vn, is based upon a
screw spacing of not less than 4 inches (100 mm) on center.
Where horizontal out-of-plane offset irregularities occur in a Type II shear wall,
portions of the wall on each side of the offset irregularity are designated as separate
Type II shear walls.
Collectors for shear transfer are provided for the full length of the Type II shear wall.
Type II shear walls have uniform top-of-wall and bottom-of-wall elevations.
Type II shear wall height, h, does not exceed 20 feet (6.1 m).

B5.2.2 Nominal Strength [Resistance]

B5.2.2.1 Type I Shear Walls
The nominal strength [resistance] for shear, Vn, shall be determined in accordance with
the following:
For h/w 2,
(Eq. B5.2.2-1)
Vn = vnw
where
h = Height of the shear wall, ft. [m].
w = Length of the shear wall, ft. [m].
vn = Nominal strength [resistance] per unit length as specified in Section B5.2.2.3,
lbs./ft. [kN/m].
Where permitted in Tables B5.2.2.3-1, B5.2.2.3-2 and Section B5.2.2.3.2.1, the nominal
strength [resistance] for shear, Vn, for height-to-length aspect ratios (h/w) greater than
2:1, but not exceeding 4:1, shall be determined in accordance with the following:
For 2 < h/w 4,
(Eq. B5.2.2-2)
Vn = vnw(2w/h)
B5.2.2.2 Type II Shear Walls
The nominal strength [resistance] for shear, Vn, shall be determined in accordance with
the following:
(Eq. B5.2.2-3)
Vn = CavnLi
where
Ca = Shear resistance adjustment factor from Table B5.2.2.2-1. For intermediate
values of opening height ratio and percentages of full-height sheathing, the
shear resistance adjustment factors are permitted to be determined by
interpolation.

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AISI S240-15

vn = Nominal strength [resistance] per unit length as specified in Section B5.2.2.3,

lbs./ft. [kN/m].
Li = Sum of lengths of Type II shear wall segments, ft. [m].
The percent of full-height sheathing shall be calculated as the sum of lengths (Li) of
Type II shear wall segments divided by the total length of the Type II shear wall including
openings.
The maximum opening height ratio shall be calculated by dividing the maximum
opening clear height by the shear wall height, h.
Table B5.2.2.2-1
Shear Resistance Adjustment Factor, Ca

Percent Full-Height Sheathing

10%
20%
30%
40%
50%
60%
70%
80%
90%
100%

1/3

Maximum Opening Height Ratio

1/2
2/3
5/6

1.00
1.00
1.00
1.00
1.00
1.00
1.00
1.00
1.00
1.00

Shear Resistance Adjustment Factor

0.69
0.53
0.43
0.71
0.56
0.45
0.74
0.59
0.49
0.77
0.63
0.53
0.80
0.67
0.57
0.83
0.71
0.63
0.87
0.77
0.69
0.91
0.83
0.77
0.95
0.91
0.87
1.00
1.00
1.00

0.36
0.38
0.42
0.45
0.50
0.56
0.63
0.71
0.83
1.00

B5.2.2.3 Nominal Strength [Resistance] per Unit Length

B5.2.2.3.1 General Requirements
Type I shear walls and Type II shear walls shall conform to the following
requirements:
(a) Wall studs and track are ASTM A1003 Structural Grade 33 (Grade 230) Type H
steel for members with a designation thickness of 33 and 43 mils, and ASTM A1003
Structural Grade 50 (Grade 340) Type H steel for members with a designation
thickness equal to or greater than 54 mils.
(b) Studs are C-shape members with a minimum flange width of 1-5/8 in. (41.3 mm),
minimum web depth of 3-1/2 in. (89 mm) and minimum edge stiffener of 3/8 in.
(9.5 mm).
(c) Track has a minimum flange width of 1-1/4 in. (31.8 mm) and a minimum web
depth of 3-1/2 in. (89 mm).
(d) Screws for structural members are a minimum No. 8 and are in accordance with
ASTM C1513.
(e) Panels less than 12 inches (305 mm) wide are not used.
(f) Maximum stud spacing is 24 inches (610 mm) on center.
(g) All sheathing edges are attached to structural members or panel blocking, unless
otherwise specified.
(h) Where used as panel blocking, flat strap is a minimum thickness of 33 mils with a
minimum width of 1-1/2 inches (38.1 mm).
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North American Standard For Cold-Formed Steel Structural Framing, 2015 Edition

B5.2.2.3.2 Steel Sheet Sheathing

The nominal strength [resistance] per unit length for assemblies with steel sheet
sheathing and panel blocking shall be as specified in Table B5.2.2.3-1 or determined in
accordance with Section B5.2.2.3.2.1.
The nominal strength [resistance] per unit length for unblocked assemblies with
panel edges overlapped and attached to each other with screw spacing as required for
panel edges in lieu of panel blocking shall be as specified in Table B5.2.2.3-1 multiplied
by 0.70.
Tabulated values in Table B5.2.2.3-1 shall be applicable for any load duration.
Systems tabulated in Table B5.2.2.3-1 shall conform to the following additional
requirements:
(a) Steel sheet sheathing has a minimum designation thickness as specified in Table
B5.2.2.3-1 and complies with ASTM A1003 Structural Grade 33 (Grade 230) Type
H.
(b) In Canada, steel sheet sheathing is connected without horizontal joints.
(c) Screws used to attach steel sheets are a minimum No. 8 and are in accordance with
ASTM C1513.
B5.2.2.3.2.1 Effective Strip Method
The effective strip method is permitted to be used only in the United States and
Mexico. The nominal shear strength [resistance] per unit length for assemblies with
steel sheet sheathing shall be determined in accordance with the following:
Vn = minimum( 1.23Pn cos , 1.23w e tFy cos )
(Eq. B5.2.2.3.2.1-1)
where
Pn = Nominal shear strength [resistance] of screw connections within the
effective strip width, We, on the steel sheet sheathing

= Arctan(h/w)
(Eq. B5.2.2.3.2.1-2)
t
= Design thickness of steel sheet sheathing
Fy = Yield stress of steel sheet sheathing
we = wmax
when 0.0819
(Eq. B5.2.2.3.2.1-3)
= wmax
when > 0.0819
(Eq. B5.2.2.3.2.1-4)
where
(Eq. B5.2.2.3.2.1-5)
wmax = w/sin

1 0.55( 0.08)0.12

0.12
a a
= 1.736 1 22
1 2 3 a
where
1 =
=
2 =
=
1 =

Fush/45
Fush/310.3
Fuf/45
Fuf/310.3
tsh/0.018

(Eq. B5.2.2.3.2.1-6)
(Eq. B5.2.2.3.2.1-7)

(For Fush in ksi)

(For Fush in MPa)
(For Fuf in ksi)
(For Fuf in MPa)
(For tsh in inches)

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(Eq. B5.2.2.3.2.1-8)
(Eq. B5.2.2.3.2.1-9)
(Eq. B5.2.2.3.2.1-10)
(Eq. B5.2.2.3.2.1-11)
(Eq. B5.2.2.3.2.1-12)

AISI S240-15

= tsh/0.457 (For tsh in mm)

(Eq. B5.2.2.3.2.1-13)
2 = tf/0.018
(For tf in inches)
(Eq. B5.2.2.3.2.1-14)
(For tf in mm)
(Eq. B5.2.2.3.2.1-15)
= tf/0.457
3 = s/6
(For s in inches)
(Eq. B5.2.2.3.2.1-16)
= s/152.4
(For s in mm)
(Eq. B5.2.2.3.2.1-17)
Fush= Tensile strength of steel sheet sheathing
Fuf = Minimum tensile strength of framing materials
Tsh = Design thickness of steel sheet sheathing
Tf = Minimum design thicknesses of framing members
s = Screw spacing on the panel edges
a = Wall aspect ratio (h:w)
= h/w
(Eq. B5.2.2.3.2.1-18)
B5.2.2.3.2.1.1 The effective strip method is permitted to be used within the
following range of parameters:
(a) Designation thickness of stud, track, and stud blocking: 33 mils (0.838 mm)
to 54 mils (1.37 mm).
(b) Designation thickness of steel sheet sheathing: 18 mils (0.457 mm) to 33 mils
(0.838 mm).
(c) Screw spacing at panel edges: 2 in. (50.8 mm) to 6 in. (152 mm).
(d) Height-to-width aspect ratio (h:w): 1:1 to 4:1.
(e) Sheathing screw shall be minimum No. 8.
(f) Yield stress of steel sheet sheathing shall not be greater than 50 ksi (345
MPa).
See Section B5.2.2.1 for Type I shear wall height-to-length aspect ratios (h/w)
greater than 2:1, but not exceeding 4:1, for additional requirements.
B5.2.2.3.3 Wood Structural Panel Sheathing
The nominal strength [resistance] per unit length for assemblies with wood structural
panel sheathing and panel blocking shall be as specified in Table B5.2.2.3-2.
In the United States and Mexico, increases in the nominal strengths [resistances] in
Table B5.2.2.3-2, as allowed by other standards, shall not be permitted.
Tabulated values in Table B5.2.2.3-2 shall be applicable for short-term load
duration only (wind or seismic loads). In the United States and Mexico, for loads of
normal or permanent load duration as defined by the AWC NDS, the values shall be
multiplied by 0.63 (normal) or 0.56 (permanent). In Canada, for loads of permanent
term load duration (dead), the values shall be multiplied by 0.56. For standard term
load duration (snow and occupancy), the values shall be multiplied by 0.80. For other
permanent and standard load combinations where the specified dead load is greater
than the specified standard term load, the values shall be multiplied by a factor equal
to 0.8 0.43 log (D/ST) 0.56, where D = specified dead load and ST = specified
standard term load based on snow or occupancy loads acting alone or in combination.
Systems tabulated in Table B5.2.2.3-2 shall conform to the following additional
requirements:
(a) Wood structural panel sheathing is manufactured using exterior glue and complies
with the following, as applicable:

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North American Standard For Cold-Formed Steel Structural Framing, 2015 Edition

(1) In the United States and Mexico, DOC PS 1 or PS 2.

(2) In Canada, CSA O121, O151 or CAN/CSA O325.0.
(b) Wood structural panels are applied either parallel to or perpendicular to studs.
(c) Screws used to attach wood structural panels are a minimum No. 8 with a minimum
head diameter of 0.285 inch (7.24 mm) and are in accordance with ASTM C1513.
B5.2.2.3.4 Gypsum Board Panel Sheathing
The nominal strength [resistance] per unit length for assemblies with gypsum board
panel sheathing and panel blocking shall be as specified in Table B5.2.2.3-3.
The nominal strength [resistance] per unit length for unblocked assemblies shall be
as specified in Table B5.2.2.3-3 multiplied by 0.35.
Tabulated values in Table B5.2.2.3-3 shall be applicable for short-term load
duration only (wind or seismic loads).
Systems tabulated in Table B5.2.2.3-3 shall conform to the following additional
requirements:
(a) Gypsum board panels comply with ASTM C1396/C1396M.
(b) Gypsum board panels are applied perpendicular to studs with panel blocking
behind the horizontal joint and with stud blocking between the first two end studs,
at each end of the wall, or applied vertically with all edges attached to structural
members.
(c) Screws used to attach gypsum board are a minimum No. 6 and are in accordance
with ASTM C954 or ASTM C1002, as applicable.
B5.2.2.3.5 Fiberboard Panel Sheathing
The nominal strength [resistance] per unit length for assemblies with fiberboard panel
sheathing and panel blocking shall be as specified in Table B5.2.2.3-4.
Tabulated values in Table B5.2.2.3-4 shall be applicable for short-term load
duration only (wind loads only).
Systems tabulated in Table B5.2.2.3-4 shall conform to the following additional
requirements:
(a) Fiberboard panels comply with ASTM C208.
(b) Fiberboard is applied perpendicular to studs with panel blocking behind the
horizontal joint and with stud blocking between the first two end studs, at each end
of the wall, or applied vertically with all edges attached to structural members.
(c) Screws used to attach fiberboard are a minimum No. 8 and are in accordance with
ASTM C1513. Head style is selected to provide a flat bearing surface in contact
with the sheathing with a head diameter not less than 0.43 inches (10.9 mm).
Screws are driven so that their flat bearing surface is flush with the surface of the
sheathing.
B5.2.2.3.6 Combined Systems
For a Type I shear wall sheathed with the same material and fastener spacing on
opposite faces of the same wall, the nominal strength [resistance] of the complete wall
based on Tables B5.2.2.3-1 through B5.2.2.3-4 shall be determined by adding the
nominal strength [resistance] from the two opposite faces together.
For a Type I shear wall having more than a single sheathing material or fastener
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AISI S240-15

spacing, the nominal strength [resistance] of the complete wall based on Tables B5.2.2.31 through B5.2.2.3-4 shall not be permitted to be determined by adding the nominal
strength [resistance] from the different individual walls; rather, it shall be determined
in accordance with the following:
(a) For a Type I shear wall having more than a single sheathing material or fastener
configuration along one face of the same wall line, the nominal strength [resistance]
shall be taken either assuming the weaker (lower nominal strength [resistance])
material or fastener configuration exists for the entire length of the wall, or the
stronger (higher nominal strength [resistance]) material or fastener configuration
exists for its own length, whichever is greater.
(b) In the United States and Mexico, for a Type I shear wall sheathed with 15/32 in.
structural 1 sheathing (4-ply) or 7/16 in. rated sheathing (OSB) on one side with
screw spacing at 6 inches (150 mm) o.c. edge and 12 inches (300 mm) o.c. field and
with 1/2 in. gypsum board on the opposite side with screw spacing at 7 in. (178
mm) o.c. edge and 7 in. (178 mm) o.c. field, the nominal strengths in Table B5.2.2.3-2
are permitted to be increased by 30 percent.
(c) For other cases of a Type I shear wall having more than a single sheathing material
or fastener configuration on opposite faces of the wall, the nominal strength
[resistance] shall be taken either assuming the weaker material or fastener
configuration exists for both faces of the wall, or the stronger material or fastener
configuration exists for its own face alone, whichever is greater.

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North American Standard For Cold-Formed Steel Structural Framing, 2015 Edition

Table B5.2.2.3-1
Unit Nominal Shear Strength [Resistance] (vn) 1, 2

For Shear Walls with Steel Sheet Sheathing on One Side of Wall

United States and Mexico

(Pounds Per Foot)

Sheathing
0.018
steel sheet
0.027
steel sheet
0.030
steel sheet

0.033
steel sheet

Fastener Spacing at Panel

Edges/Field
(inches)

Max.
Aspect
Ratio
(h/w)

Stud
Blocking
Required

Designation
Thickness of
Stud, Track and
Blocking (mils)

Required
Sheathing
Screw Size

6/12

4/12

3/12

2/12

2:1

485

33 (min.)

4:1 3

1,000

1085

1170

43 (min.)

4:1 3

645

710

780

845

33 (min.)

4:1 3

795

960

1005

1055

33 (min.)

4:1 3

910

1015

1040

1070

43 (min.)

4:1 3

1355

Yes

43 (min.)

4:1 3

1035

1145

1225

1300

33 (min.)

4:1 3

1055

1170

1235

1305

43 (min.)

4:1 3

1505

Yes

43 (min.)

4:1 3

1870

54 (min.)

4:1 3

2085

Yes

54 (min.)

Stud
Blocking
Required

Designation
Thickness of
Stud, Track and
Blocking (mils)

Required
Sheathing
Screw Size

Canada
(kN/m)

Sheathing

0.46 mm
steel sheet
0.68 mm
steel sheet
0.76 mm
steel sheet
0.84 mm
steel sheet

Max.
Aspect
Ratio
(h/w)

Fastener Spacing at Panel

Edges/Field
(mm)
150/
300

100/
300

75/
300

50/
300

2:1

4.1

33 (min)

2:1

4.5

6.0

6.8

7.5

43 (min)

2:1

7.4

9.7

11.6

13.5

Yes

43 (min)

2:1

6.5

7.2

7.9

8.7

33 (min)

4:1 3

8.9

10.6

11.6

12.5

43 (min)

2:1

11.7

14.3

Yes

43 (min)

2:1

19.9

23.3

Yes

54 (min)

4:1 3

10.7

12.0

13.0

14.0

43 (min)

1. For SI: 1 = 25.4 mm, 1 foot = 0.305 m, 1 lb = 4.45 N.

2. See Section B5.2.2.3.6 for requirements for sheathing applied to both sides of wall.
3. See Section B5.2.2.1 for Type I shear wall height-to-length aspect ratios (h/w) greater than 2:1, but not exceeding 4:1.

This document is copyrighted by AISI. Any redistribution is prohibited.

AISI S240-15

Table B5.2.2.3-2
Unit Nominal Shear Strength [Resistance] (vn) 1, 2

For Shear Walls with Wood Structural Panel Sheathing on One Side of Wall

United States and Mexico

(Pounds Per Foot)

Maximum
Aspect
Ratio
(h/w)

Sheathing

Fastener Spacing at Panel Edges/Field

(inches)
6/12

4/12

3/12

2/12

Designation
Thickness of
Stud, Track
and
Blocking
(mils)

15/32 structural 1 (4-ply)

2:1

1065

1410

1735

1910

43 (min.)

7/16 rated sheathing (OSB)

7/16 rated sheathing (OSB)
oriented perpendicular to
framing
7/16 rated sheathing (OSB)

2:1

910

1410

1735

1910

33 (min.)

2:1

1020

33 (min.)

4:1 3

1025

1425

1825

33 (min.)

Canada
(kN/m)
Maximum
Aspect
Ratio
(h/w)

Sheathing

Fastener Spacing at Panel Edges/Field

(mm)
150/300

100/300

75/300

Designation
Thickness of
Stud, Track
and
Blocking
(mils)

9.5 mm CSP Sheathing

4:1 3

8.5

11.8

14.2

43 (min.)

12.5 mm CSP Sheathing

4:1 3

9.5

13.0

19.4

43 (min.)

12.5 mm DFP Sheathing

4:1 3

11.6

17.2

22.1

43 (min.)

9 mm OSB 2R24/W24

4:1 3

9.6

14.3

18.2

43 (min.)

11 mm OSB 1R24/2F16/W24

4:1 3

9.9

14.6

18.5

43 (min.)

1. For SI: 1 = 25.4 mm, 1 foot = 0.305 m, 1 lb = 4.45 N.

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North American Standard For Cold-Formed Steel Structural Framing, 2015 Edition

Table B5.2.2.3-3
Unit Nominal Shear Strength [Resistance] (vn) 1, 2

For Shear Walls with Gypsum Board Panel Sheathing on One Side of Wall

United States and Mexico

(Pounds Per Foot)

Maximum
Aspect
Ratio
(h/w)

Sheathing

gypsum board

2:1

Fastener Spacing at Panel Edges/Field

(inches)
8/12

4/12

7/7

4/4

230

295

290

425

Designation
Thickness of
Stud, Track
and
Blocking
(mils)
33 (min)

Canada
(kN/m)
Maximum
Aspect
Ratio
(h/w)

Sheathing

12.5 mm gypsum board

2:1

Fastener Spacing at Panel Edges/Field

(mm)
200/300

150/300

100/300

2.7

3.1

3.4

Designation
Thickness of
Stud, Track
and
Blocking
(mils)
33 (min)

1. For SI: 1 = 25.4 mm, 1 foot = 0.305 m, 1 lb = 4.45 N.

2. See Section B5.2.2.3.6 for requirements for sheathing applied to both sides of wall.

Table B5.2.2.3-4
Unit Nominal Shear Strength [Resistance] (vn) 1, 2

For Shear Walls with Fiberboard Panel Sheathing on One Side of Wall

United States and Mexico

(Pounds Per Foot)

Sheathing

fiberboard

Maximum
Aspect
Ratio
(h/w)
1:1

Fastener Spacing at Panel Edges/Field

(inches)
4/6

3/6

2/6

425

615

670

Designation
Thickness of
Stud, Track
and
Blocking
(mils)
33 (min)

Canada
(kN/m)

Sheathing

12.5 mm fiberboard

Maximum
Aspect
Ratio
(h/w)
1:1

Fastener Spacing at Panel Edges/Field

(mm)
100/150

75/150

50/150

5.0

7.2

7.8

1. For SI: 1 = 25.4 mm, 1 foot = 0.305 m, 1 lb = 4.45 N.

2. See Section B5.2.2.3.6 for requirements for sheathing applied to both sides of wall.

This document is copyrighted by AISI. Any redistribution is prohibited.

Designation
Thickness of
Stud, Track
and
Blocking
(mils)
33 (min)

AISI S240-15

B5.2.3 Available Strength [Factored Resistance]

The available strength [factored resistance] (vVn for LRFD and LSD or Vn/v for ASD)
shall be determined from the nominal strength [resistance] using the applicable safety factors
() or resistance factors () given in this section in accordance with the applicable design
method ASD, LRFD, or LSD as follows:
v = 2.00 for ASD
v = 0.65 for LRFD
v = 0.70 for LSD (except gypsum and fiberboard sheathed walls)
v = 0.60 for LSD (gypsum and fiberboard sheathed walls)
B5.2.4 Collectors and Anchorage
Design of collectors and anchorage for shear walls shall conform to the requirements of
this section.
B5.2.4.1 Collectors and Anchorage for In-Plane Shear
Collectors and anchorage for in-plane shear shall be designed in accordance with this
section.
B5.2.4.1.1 Type I Shear Walls
The unit shear force, v, transmitted into the top and out of the base of the Type I
shear wall shall be determined in accordance with the following:
V
v=
(Eq. B5.2.4-1)
L
where
v = Unit shear force, plf [kN/m]
V = Shear force determined in accordance with applicable ASD, LRFD or LSD
load combinations in Type I shear wall, lbs [kN]
L = Length of Type I shear wall, feet [m]
B5.2.4.1.2 Type II Shear Walls
The unit shear force, v, transmitted into the top and out of the base of the Type II
shear wall segments, and into collectors connecting Type II shear wall segments, shall be
determined in accordance with the following:
V
v=
(Eq. B5.2.4-2)
Ca Li
where
v = Unit shear force, plf [kN/m]
V = Shear force determined in accordance with applicable ASD, LRFD or LSD
load combinations in Type II shear wall, lbs [kN]
Ca = Shear resistance adjustment factor from Table B5.2.2.2-1
Li = Sum of Lengths of Type II shear wall segments, feet [m]

B5.2.4.2 Uplift Anchorage at Wall Ends

Uplift anchorage at shear wall ends shall be designed in accordance with this section.

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North American Standard For Cold-Formed Steel Structural Framing, 2015 Edition

B5.2.4.2.1 General
Where uplift anchorage resists the overturning load from the story or stories
above, the anchorage shall be sized for the anchorage force resulting from the lateral
forces at its level plus the story or stories above.
Hold-downs shall be designed to resist the sum of both shear wall overturning and
roof uplift, as applicable.
Uplift anchorage forces are permitted to be reduced to account for dead load in
accordance with the applicable building code.
B5.2.4.2.2 Type I Shear Walls
Anchorage for uplift forces due to overturning shall be provided at each end of
the Type I shear wall. The uplift anchorage force contributed from each level shall be
determined in accordance with the following:
Vh
(Eq. B5.2.4-3)
C=
L
where
C = Uplift anchorage force contributed from each level, lbs [kN]
V = Shear force determined in accordance with applicable ASD, LRFD or LSD
load combinations in Type I shear wall, lbs [kN]
h = Shear wall height, feet [m]
L = Length of Type I shear wall including anchor offsets, feet [m]
B5.2.4.2.3 Type II Shear Walls
Anchorage for uplift forces due to overturning shall be provided at each end of
the Type II shear wall. For each level, the uplift anchorage force contributed shall be
determined in accordance with the following:
Vh
(Eq. B5.2.4-4)
C=
Ca Li
where
C = Uplift anchorage force contributed from each level, lbs [kN]
V = Shear force determined in accordance with applicable ASD, LRFD or LSD
load combinations in Type II shear wall, lbs [kN]
h = Shear wall height, feet [m]
Ca = Shear resistance adjustment factor from Table B5.2.2.2-1
Li = Sum of lengths of Type II shear wall segments, feet [m]

B5.2.4.3 Uplift Anchorage Between Type II Shear Wall Ends

In addition to the requirements of Section B5.2.4.2, Type II shear wall bottom plates at
full-height sheathing locations shall be anchored for a uniform uplift force equal to the
unit shear force, v, determined in accordance with Section B5.2.4.1 plus any applicable
roof uplift forces.
B5.2.5 Design Deflection
The deflection of a blocked Type I shear wall with steel sheet sheathing or wood structural
panel sheathing shown in Tables B5.2.2.3-1 and B5.2.2.3-2 is permitted to be calculated in
accordance with the following:
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AISI S240-15
2

v
2 vh 3
vh
h
+ 1 2
+ 1 5 / 4 2 3 4 + v
Gt sheathing
b
3E s A c b
b

(Eq. B5.2.5-1)

where
Ac = Gross cross-sectional area of chord member, in square inches (mm2)
b
= Length of the shear wall, in inches (mm)
Es = Modulus of elasticity of steel
= 29,500,000 psi (203,000 MPa)
G = Shear modulus of sheathing material, in pounds per square inch (MPa)
h
= Wall height, in inches (mm)
s
= Maximum fastener spacing at panel edges, in inches (mm)
tsheathing = Nominal panel thickness, in inches (mm)
tstud = Framing designation thickness, in inches (mm)
v
= Shear demand, in pounds per linear inch (N/mm)
= V/b
(Eq. B5.2.5-2)
V = Total lateral load applied to the shear wall, in pounds (N)

= 67.5 for plywood other than Canadian Soft Plywood (CSP),

= 55 for OSB and CSP for U.S. Customary units (lb/in1.5)
= 2.35 for plywood other than CSP,
= 1.91 for OSB and CSP for SI units (N/mm1.5)
= 29.12(tsheathing/0.018)
for sheet steel (for tsheathing in inches) (lb/in1.5)
(Eq. B5.2.5-3a)
for sheet steel (for tsheathing in mm) (N/mm1.5)
= 1.01(tsheathing/0.457)
(Eq. B5.2.5-3b)

= Calculated deflection, in inches (mm)

v = Vertical deformation of anchorage/attachment details, in inches (mm)

= 1.85 for plywood other than CSP, 1.05 for OSB and CSP
= 0.075 (tsheathing/0.018) for sheet steel (for tsheathing in inches)
(Eq. B5.2.5-4a)
= 0.075(tsheathing/0.457) for sheet steel (for tsheathing in mm)
(Eq. B5.2.5-4b)
(Eq. B5.2.5-5)
1 = s/6 (for s in inches) and s/152.4 (for s in mm)
2 = 0.033/tstud (for tstud in inches) and
(Eq. B5.2.5-6a)
= 0.838/tstud (for tstud in mm)
(Eq. B5.2.5-6b)
3
4

( h / b)
2
= 1 for wood structural panels

(Eq. B5.2.5-7)

33
(for Fy in ksi)
Fy

(Eq. B5.2.5-8a)

227.5
(for Fy in MPa) for sheet steel
Fy

(Eq. B5.2.5-8b)

The deflection of a Type I shear wall with gypsum panel sheathing or fiberboard
sheathing or Type II shear wall shall be determined by principles of mechanics considering
the deformation of the sheathing and its attachment, chord studs and hold-downs.

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North American Standard For Cold-Formed Steel Structural Framing, 2015 Edition

B5.3 Strap Braced Wall Design

Strap braced walls shall be designed in accordance with the requirements of this section
and shall be installed in accordance with the requirements of Section C3.6.2.
User Note:

See Section A1.3 for applicability of this section to cold-formed steel structural members
and connections in seismic force-resisting systems.
B5.3.1 General
The height-to-length aspect ratio of a strap braced wall shall not exceed 2:1 unless a
rational engineering analysis is performed which includes joint flexibility and end moments
in the design of the chord studs.
B5.3.2 Nominal Strength [Resistance]
The nominal strength [resistance] for the strap, connections, and chord studs shall be
determined in accordance with AISI S100.
B5.3.3 Available Strength [Factored Resistance]
The available strength [factored resistance] for the strap, connections, and chord studs shall
be determined in accordance with AISI S100.
B5.3.4 Collectors and Anchorage
Design of collectors and anchorage for strap braced walls shall conform to the
requirements of this section.
B5.3.4.1 Collectors and Anchorage for In-Plane Shear
Collectors and anchorage shall be designed to transmit the shear force into the top
and out of the base of the strap braced wall.
B5.3.4.2 Uplift Anchorage at Wall Ends
Where uplift anchorage resists the overturning load from the story or stories above,
the anchorage shall be sized for the anchorage force at its level plus the anchorage force
of the story or stories above.
Hold-downs shall be designed to resist the sum of both strap braced wall overturning
and roof uplift, as applicable.
Uplift anchorage forces are permitted to be reduced to account for dead load in
accordance with the applicable building code.
Anchorage for uplift forces due to overturning shall be provided at each end of the
strap braced wall. Uplift anchorage and boundary chord forces shall be determined in
accordance with the following:
Vh
(Eq. B5.3.4.2-1)
C=
L
where
C = Boundary chord force (tension/compression), lbs [kN]
V = Shear force determined in accordance with applicable ASD, LRFD or LSD load
combinations in strap braced wall, lbs [kN]
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AISI S240-15

h = Strap braced wall height, feet [m]

L = Length of strap braced wall including anchor offsets, feet [m]
B5.3.5 Design Deflection
The deflection of a strap braced wall shall be determined by principles of mechanics
considering the deformation of the strap, chord studs and hold-downs.
B5.4 Diaphragm Design
Diaphragms shall be designed based on principles of mechanics in accordance with Section
B1.2.6 or tests in accordance with Section B5.4.5. Alternatively, in the United States and
Mexico, diaphragms sheathed with wood structural panels are permitted to be designed as either
blocked diaphragms or unblocked diaphragms in accordance with the requirements of Sections
B5.4.1 through B5.4.4 and shall be installed in accordance with the requirements of Section
C3.6.3.
B5.4.1 General
Diaphragms shall conform to the following requirements:
(a) The aspect ratio (length/width) of the diaphragm does not exceed 4:1 for blocked
diaphragms and 3:1 for unblocked diaphragms.
(b) Joists and track are ASTM A1003 Structural Grade 33 (Grade 230) Type H steel for
members with a designation thickness of 33 and 43 mils, and ASTM A1003 Structural
Grade 50 (Grade 340) Type H steel for members with a designation thickness equal to or
greater than 54 mils.
(c) The minimum designation thickness of structural members is 33 mils.
(d) Joists are C-shape members with a minimum flange width of 1-5/8 in. (41.3 mm),
minimum web depth of 3-1/2 in. (89 mm) and minimum edge stiffener of 3/8 in. (9.5
mm).
(e) Track has a minimum flange width of 1-1/4 in. (31.8 mm) and a minimum web depth of
3-1/2 in. (89 mm).
(f) Screws for structural members are a minimum No. 8 and are in accordance with ASTM
C1513.
(g) Wood structural panel sheathing is manufactured using exterior glue and complies with
DOC PS 1 or PS 2.
(h) Screws used to attach wood structural panels are minimum No. 8 where structural
members have a designation thickness of 54 mils or less and No. 10 where structural
members have a designation thickness greater than 54 mils and are in accordance with
ASTM C1513.
(i) Screws in the field of the panel are attached to intermediate supports at a maximum 12inch (305 mm) spacing along the structural members.
(j) Panels less than 12 inches (305 mm) wide are not used.
(k) Maximum joist spacing is 24 inches (610 mm) on center.
(l) Where diaphragms are designed as blocked, all panel edges are attached to structural
members or panel blocking.
(m) Where used as panel blocking, flat strap is a minimum thickness of 33 mils with a
minimum width of 1-1/2 inches (38.1 mm).

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North American Standard For Cold-Formed Steel Structural Framing, 2015 Edition

B5.4.2 Nominal Strength

The nominal strength per unit length for blocked and unblocked assemblies shall be as
specified in Table B5.4.2-1.
Tabulated values in Table B5.4.2-1 are applicable for short-term load duration only
(wind or seismic loads). For loads of normal or permanent load duration as defined by the
AWC NDS, the values shall be multiplied by 0.75 (normal) or 0.67 (permanent).
Table B5.4.2-1
Nominal Shear Strength (Rn) per Unit Length for Diaphragms With Wood Structural Panel Sheathing 1
United States and Mexico
(Pounds Per Foot)

Sheathing

Thickness

Blocked

Unblocked

Screw spacing at diaphragm

boundary edges and at all
continuous panel edges (in.)

Screws spaced maximum of 6 in. on

all supported edges

2.5

Load
perpendicular to
unblocked
edges and
continuous
panel joints

3/8

768

1022

1660

2045

685

510

7/16

768

1127

1800

2255

755

565

15/32

925

1232

1970

2465

825

615

3/8

690

920

1470

1840

615

460

7/16

760

1015

1620

2030

680

505

15/32

832

1110

1770

2215

740

555

(in.)

Screw spacing at all

other panel edges (in.)

Structural I

C-D, C-C and other

graded wood
structural panels
1.

All other
configurations

For SI: 1 in. = 25.4 mm, 1 foot = 0.305 m, 1 lb = 4.45 N.

B5.4.3 Available Strength

The available strength (vVn for LRFD or Vn/v for ASD) shall be determined from the
nominal strength using the applicable safety factors () or resistance factors () given in this
section in accordance with the applicable design method ASD or LRFD, as follows:
v = 2.00 (ASD)
v = 0.65 (LRFD)
B5.4.4 Design Deflection
The deflection of a blocked diaphragm with wood structural panel sheathing shown in
Table B5.4.2-1 is permitted to be calculated in accordance with Section B5.4.4.1. The
deflection of an unblocked diaphragm with wood structural panel sheathing shown in Table
B5.4.2-1 is permitted to be calculated in accordance with Section B5.4.4.2.

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AISI S240-15

B5.4.4.1 Blocked Diaphragms

The deflection of a blocked diaphragm, b, is permitted to be determined in
accordance with the following:
n

ci X i

v
j=1
0.052 vL3
vL
b =
+ 1 2
+ 1 5 / 4 2 (a ) +
Gt sheathing
EsA c b
2b
2b

(Eq. B5.4.4-1)

where
Ac = Gross cross-sectional area of chord member, in square inches (mm2)
b
= Diaphragm depth parallel to direction of load, in inches (mm)
Es = Modulus of elasticity of steel
= 29,500,000 psi (203,000 MPa)
G = Shear modulus of sheathing material, in pounds per square inch (MPa)
L
= Diaphragm length perpendicular to direction of load, in inches (mm)
n
= Number of chord splices in diaphragm (considering both diaphragm chords)
s
= Maximum fastener spacing at panel edges, in inches (mm)
tsheathing= Nominal panel thickness, in inches (mm)
tstud = Nominal framing thickness, in inches (mm)
v
= Shear demand, in pounds per linear inch (N/mm)
= V/(2b)
(Eq. B5.4.4-2)
V = Total lateral load applied to the diaphragm, in pounds (N)
Xi = Distance between the ith chord-splice and the nearest support, in inches
(mm)

= Ratio of the average load per fastener based on a non-uniform fastener

pattern to the average load per fastener based on a uniform fastener pattern
(= 1 for a uniformly fastened diaphragm)

= 67.5 for plywood other than Canadian Soft Plywood (CSP)

= 55 for OSB and CSP for U.S. Customary units (lb/in1.5)
= 2.35 for plywood other than CSP
= 1.91 for OSB for SI units (N/mm1.5)
b = Calculated deflection, in inches (mm)
ci = Deformation value associated with ith chord splice, in inches (mm)

= 1.85 for plywood other than CSP

= 1.05 for OSB and CSP
(Eq. B5.4.4-3a)
1 = s/6 (for s in inches)
= s/152.4 (for s in mm)
(Eq. B5.4.4-3b)
(Eq. B5.4.4-4a)
2 = 0.033/tstud (for tstud in inches)
(Eq. B5.4.4-4b)
= 0.838/tstud (for tstud in mm)
B5.4.4.2 Unblocked Diaphragms
The deflection of an unblocked diaphragm, ub, is permitted to be determined in
accordance with the following:
(Eq. B5.4.4-5)
ub = 2.50 b

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North American Standard For Cold-Formed Steel Structural Framing, 2015 Edition

where
b = Deflection of blocked diaphragm determined in accordance with Eq. B5.4.4-1
B5.4.5 Beam Diaphragm Tests for Non-Steel Sheathed Assemblies
For buildings with the maximum aspect ratio of 4:1 and having cold-formed steel roof or
floor assemblies having non-steel sheathing, the in-plane diaphragm nominal shear strength
[resistance], Sn, shall be in accordance with Table B5.4.2-1 where applicable or shall be
established by test in accordance with ASTM E455 and AISI S100 Section F1.1(a).
When the failure mode of the assembly is identified to be in the cold-formed steel
members or sheathing-to-steel fasteners, safety factors shall not be less than and resistance
factors shall not be greater than those prescribed by Section B5.2.3 when determined in
accordance with the procedures of AISI S100 Section F1.1 with the following definitions of
the variables:
o = Target reliability index
= 2.5 for USA and Mexico and
= 3.0 for Canada
Fm = Mean value of the fabrication factor
= 1.0
Mm= Mean value of the material factor
= 1.1
VM = Coefficient of variation of material factor
= 0.10
VF = Coefficient of variation of fabrication factor
= 0.10
VQ = Coefficient of variation of the load effect
= 0.21
VP = Actual calculated coefficient of variation of the test results, without limit
n = Number of connections in the assembly with the same tributary area
When the failure mode of the assembly is identified to be in the sheathing material, a
safety factor of 2.8 and resistance factor of 0.6 shall be used.

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AISI S240-15

C. INSTALLATION
C1 General
Structural members and connections shall be installed in accordance with the requirements of
this section, as applicable.
C2 Material Condition
The following requirements shall apply to structural members, connectors, hold-downs and
mechanical fasteners:
(a) Structural members, connectors, hold-downs and mechanical fasteners shall be as specified by
the approved construction documents.
(b) Damaged structural members, connectors, hold-downs and mechanical fasteners shall be
replaced or repaired in accordance with an approved design or as specified by a registered
design professional.
C2.1 Web Holes
Holes in webs of framing members shall be in conformance with AISI S100 [CSA S136], the
approved construction documents, or shall be reinforced or patched in accordance with an
approved design as specified by a registered design professional.
C2.2 Cutting and Patching
C2.2.1 All cutting of framing members shall be done by sawing, abrasive cutting,
shearing, plasma cutting or other approved methods acceptable to the registered design
professional.
C2.2.2 Cutting or notching of structural members, including flanges and lips of joists, studs,
headers, rafters, and ceiling joists, shall be permitted with an approved design or as
specified by a registered design professional.
C2.2.3 Patching of cuts and notches shall be permitted with an approved design or as
specified by a registered design professional.
C2.3 Splicing
Splicing of joists, studs and other structural members shall be permitted with an approved
design or as specified by a registered design professional.
C3 Structural Framing
Structural members shall be installed in accordance with the requirements of this section, as
applicable.
C3.1 Foundation
The foundation shall be level and free from defects beneath structural walls. If the
foundation is not level, provisions shall be made to provide a uniform bearing surface with a
maximum 1/4 inch (6.4 mm) gap between the bottom track or rim track and the foundation.
This shall be accomplished through the use of load bearing shims or grout provided between
the underside of the wall bottom track or rim track and the top of the foundation wall or slab
at stud or joist locations.

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North American Standard For Cold-Formed Steel Structural Framing, 2015 Edition

C3.2 Ground Contact

Framing shall not be in direct contact with the ground unless permitted by an approved
design. Framing not in direct contact with the ground shall be installed at a height above the
ground in accordance with the applicable building code.
C3.3 Floors
C3.3.1 Plumbness and Levelness
Floor joists and floor trusses shall be installed plumb and level, except where designed
as sloping members.
C3.3.2 Alignment
Floor joists and floor trusses shall comply with the in-line framing requirements of
Section B1.2.3 and floor sheathing span capacity requirements of Section B1.2.4, as
applicable.
C3.3.3 Bearing Width
Floor joists and floor trusses shall be installed with full bearing over the width of the
bearing wall beneath, a minimum 1-1/2 inch (38 mm) bearing end, or in accordance with
an approved design or as specified by a registered design professional.
C3.3.4 Web Separation
Floor joist webs shall not be in direct contact with rim track webs.
C3.4 Walls
C3.4.1 Straightness, Plumbness and Levelness
Wall studs shall be installed plumb and walls shall be level in accordance with ASTM
C1007, except where designed as sloping members.
C3.4.2 Alignment
Structural wall studs shall comply with the in-line framing requirements of Section
B1.2.3 and wall sheathing span capacity requirements of Section B1.2.4, as applicable.
C3.4.3 Stud-to-Track Connection
The connection between the stud flange and the track flange shall meet the requirements
of Section B3.2.5 and shall permit both ends of the wall stud to be connected to the track to
restrain rotation about the longitudinal wall stud axis and horizontal displacement
perpendicular to the wall stud axis. Further, the maximum gap between the end of the stud
and the track web shall also comply with the following, as applicable:
(a) Ends of axial load bearing wall studs 54 mils and less shall have square end cuts and
shall be seated tight against the track with a gap that does not exceed 1/8 in. (3.2 mm)
between the end of the wall framing member and the web of the track. For thicknesses
of the stud or track greater than 54 mil (0.054 inches (1.37mm)), the maximum end gap
shall be specified by the registered design professional.
(b) Ends of curtain wall studs shall have square end cuts and shall be seated in the track with

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AISI S240-15

a gap that does not exceed 1/4 in. (6.4 mm) between the end of the wall stud and the
web of the track, unless otherwise accepted by a registered design professional.
C3.4.4 Back-to-Back and Box Headers
Back-to-back and box headers designed in accordance with this Standard shall be
installed in accordance with Figures C3.4.4-1 and C3.4.4-2, respectively. For box headers, it
is permitted to connect track flanges to the webs of C-shape sections using 1-inch (25.4 mm)
fillet welds spaced at 24 inches (610 mm) on center in lieu of No. 8 screws.

Figure C3.4.4-1 Back-to-Back Header

Figure C3.4.4-2 Box Header

C3.4.5 Double and Single L-Headers

Double and single L-headers designed in accordance with this Standard shall be
installed in accordance with Figures C3.4.5-1 and C3.4.5-2, respectively.
C3.4.6 Inverted L-Header Assemblies
Inverted double or single L-headers designed in accordance with this Standard shall be
installed in accordance with the following:
(1) The horizontal leg of the inverted L-header shall be coped to permit the vertical leg to
lap over at least one bearing stud at each end. The horizontal leg after coping shall be
within 1/2 inch (12.7 mm) of the bearing stud at each end.
(2) The horizontal leg of the inverted L-header shall be attached to the head track at each
end and at 12 inches (304.8 mm) on center with minimum #8 screws.
(3) The vertical leg of the inverted L-header shall be attached to at least one bearing stud at
each end and each cripple stud with a minimum No. 8 screw top and bottom. The top
screw in the vertical leg of the inverted L-header shall be located not more than 1 inch
(25.4 mm) from the top edge of the vertical leg.

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North American Standard For Cold-Formed Steel Structural Framing, 2015 Edition

For SI: 1 inch = 25.4 mm

Figure C3.4.5-1 Double L-Header

For SI: 1 inch = 25.4 mm

Figure C3.4.5-2 Single L-Header

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AISI S240-15

C3.5 Roofs and Ceilings

C3.5.1 Plumbness and Levelness
Roof and ceiling framing members shall be installed plumb and level, except where
designed as sloping members.
C3.5.2 Alignment
Roof and ceiling framing members shall comply with the in-line framing requirements
of Section B1.2.3 and roof sheathing span capacity requirements of Section B1.2.4, as
applicable.
C3.5.3 End Bearing
Ceiling joists and roof trusses shall be installed with full bearing over the width of the
bearing wall beneath, or a minimum 1-1/2 inch (38 mm) bearing end condition, or in
accordance with an approved design or as specified by a registered design professional.
C3.6 Lateral Force-Resisting Systems
C3.6.1 Shear Walls
The installation of shear walls designed in accordance with this Standard shall conform
to the following requirements:
(a) Fasteners along the edges in shear panels are placed from panel edges not less than the
following, as applicable:
(1) In the United States and Mexico, 3/8 in. (9.5 mm).
(2) In Canada, 12.5 mm (1/2 in.).
(b) Where used as panel blocking with steel sheet sheathing, flat strap is installed on top of or
below the sheathing. Where used as panel blocking with other than steel sheet sheathing,
flat strap is installed below the sheathing.
(c) Where panel blocking is used with other than steel sheet sheathing, the screws are installed
through the sheathing to the panel blocking.
C3.6.2 Strap Braced Walls
No additional provisions.
C3.6.3 Diaphragms
The installation of diaphragms sheathed with wood structural panels and designed in
accordance with this Standard shall conform to the following requirements:
(a) Fasteners along the edges in shear panels are placed from panel edges not less than 3/8
in. (9.5 mm).
(b) Where used as panel blocking, flat strap is installed below the sheathing.
(c) Where panel blocking is used, the screws are installed through the sheathing to the panel
blocking.
C4 Connections
Connections shall be installed in accordance with the requirements of this section, as
applicable.
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North American Standard For Cold-Formed Steel Structural Framing, 2015 Edition

C4.1 Screw Connections

C4.1.1 Steel-to-Steel Screws
Use of a larger-than-specified screw size is permitted if the installation is in accordance
with the minimum design spacing and edge distance.
C4.1.2 Installation
C4.1.2.1 Screw fasteners shall extend through the steel connection with a minimum of
three (3) exposed threads.
C4.1.2.2 Screw fasteners shall penetrate individual components of connections without
causing permanent separation between components.
C4.1.3 Stripped Screws
C4.1.3.1 Stripped screw fasteners in direct tension shall not be considered effective.
C4.1.3.2 Stripped screw fasteners in shear shall only be considered effective when the
number of stripped screw fasteners considered effective does not exceed 25% of the
total number of screw fasteners considered effective in the connection.
C4.2 Welded Connections
Welded areas shall be protected with an approved treatment to retain the corrosion
resistance of the welded area.
C5 Miscellaneous
Utilities and insulation shall be installed in accordance with the requirements of this section,
as applicable.
C5.1 Utilities
C5.1.1 Holes
C5.1.1.1 Holes shall comply with the requirements specified in Section C2.1.
C5.1.1.2 Penetrations of floor, wall and ceiling/roof assemblies which are required to
have a fire resistance rating shall be protected in accordance with the approved
construction documents.
C5.1.2 Plumbing
All piping shall be provided with an isolative non-corrosive system to prevent galvanic
action or abrasion between framing members and piping.
C5.1.3 Electrical
Wiring not enclosed in metal conduit shall be separated from the framing members by
nonconductive, noncorrosive grommets or by other approved means.

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AISI S240-15

C5.2 Insulation
C5.2.1 Mineral Fiber Insulation
Mineral fiber insulation (e.g., rock wool, glass fiber, etc.) for installation within cavities
of framing members shall be full-width type insulation and shall be installed in accordance
with the applicable building code and insulation manufacturers requirements. Compression
of the insulation is permitted to occur at the open side of the C-shaped framing member.
C5.2.2 Other Insulation
Other types of insulation (e.g., foams, loose fill, etc.) for installation within cavities of
framing members shall be installed in accordance with the applicable building code and
insulation manufacturers requirements. The width of insulation shall be dimensionally
compatible with the cold-formed steel framing.

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North American Standard For Cold-Formed Steel Structural Framing, 2015 Edition

D. QUALITY CONTROL AND QUALITY ASSURANCE

D1 General
D1.1 Scope and Limits of Applicability
Chapter D provides minimum requirements for quality control and quality assurance for
material control, component manufacturing, and installation for cold-formed steel light-frame
construction. Minimum observation and inspection tasks deemed necessary to ensure quality
cold-formed steel light-frame construction are specified.
D1.2 Responsibilities
Quality control as specified in this chapter shall be provided by the component manufacturer
and installer, as applicable. Quality assurance as specified in this chapter shall be provided by
others where required by the authority having jurisdiction, the applicable building code, the
owner, or the registered design professional.
D2 Quality Control Programs
D2.1 The component manufacturer shall establish and maintain quality control procedures and
perform inspections to ensure that the work is in accordance with this Standard and the
shop drawings.
D2.2 The installer shall establish and maintain quality control procedures and perform
inspections to ensure that the work is in accordance with this Standard and the construction
documents.
D2.3 Product identification shall comply with the requirements of Section A5.5, and shall be
monitored by the component manufacturers and installers quality control inspectors, as
applicable.
D2.4 Where part of a component assembly, the component manufacturers quality control inspector
shall perform inspections of the following items, as applicable:
(a) Cold-formed steel structural members and connectors in accordance with Section D6.5.
(b) Shop welding in accordance with Section D6.6.
(c) Mechanical fastening in accordance with Section D6.7.
D2.5 The installers quality control inspector shall perform inspections of the following, as
applicable:
(a) Cold-formed steel structural members and connectors that are not part of a component
assembly in accordance with Section D6.5.
(b) Field welding in accordance with Section D6.6.
(c) Mechanical fastening that is not part of a component assembly in accordance with
Section D6.7.
(d) Installation of cold-formed steel light-frame construction in accordance with Section D6.8.
(e) Installation of cold-formed steel lateral force-resisting systems in accordance with Section
D6.9.
(f) Damage to cold-formed steel structural members and connectors, including component
assemblies damaged during or after delivery to the project.

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AISI S240-15

D3 Quality Control Documents

D3.1 Documents to be Submitted
The component manufacturer and installer shall submit the following documents to the
registered design professional and contractor for review prior to the installation of the cold-formed
steel light-frame construction:
(a) Shop drawings, unless shop drawings have been furnished by others.
(b) Installation drawings, unless installation drawings have been furnished by others.
(c) Product data sheets, catalogue data or independent evaluation reports on cold-formed
steel structural members, including material, corrosion protection, base steel thickness, and
dimensions. Alternatively, material, corrosion protection, base steel thickness, and
dimensions shall be shown on the installation drawings.
(d) Product data sheets, catalogue data or independent evaluation reports on connectors
and mechanical fasteners.
D3.1.1 Additional Requirements for Lateral Force-Resisting Systems
D3.1.1.1 Component Assemblies
For component assemblies, the component manufacturer shall submit the following
additional documents, as applicable, to the registered design professional and contractor for
approval prior to the installation of the cold-formed steel lateral force resisting system
elements:
(a) Welding procedure specifications.
(b) Mechanical fastener installation procedures.
(c) Product data sheets, catalogue data or independent evaluation reports on hold-downs.
D3.1.1.2 Other Than Component Assemblies
For other than component assemblies, the installer shall submit the following additional
documents, as applicable, to the registered design professional and contractor for approval
prior to the installation of the cold-formed steel lateral force-resisting system elements:
(a) Welding procedure specifications.
(b) Mechanical fastener installation procedures.
(c) Product data sheets, catalogue data or independent evaluation reports on hold-downs.
D3.1.1.3 Exceptions to Sections D3.1.1.1 and D3.1.1.2
The additional requirements in Section D3.1.1.1 and Section D3.1.1.2 are not required
for cold-formed steel lateral force-resisting systems where either of the following apply:
(a) The sheathing of the shear wall is gypsum board or fiberboard.
(b) The sheathing is wood structural sheathing or steel sheet sheathing on only one side of
the shear wall or diaphragm assembly and the fastener spacing of the sheathing is
more than 4 inches (102 mm) on center (o.c.).
D3.2 Available Documents
Unless required for submittal by the registered design professional, the following documents,
as applicable and upon request, shall be made available by the component manufacturer or installer,

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North American Standard For Cold-Formed Steel Structural Framing, 2015 Edition

as applicable, in electronic or printed form to the registered design professional and contractor for
review prior to installation of the cold-formed steel light-frame construction:
(a) Manufacturers installation instructions for connectors, hold-downs and mechanical
fasteners.
(b) Manufacturers product data sheets or catalog data for welding consumables, filler
metals and fluxes that include the product, limitations of use, recommended or typical
welding parameters, and storage and exposure requirements.
(c) Welding procedure specifications.
(d) Procedure qualification records for welding procedure specifications that are not
prequalified in accordance with AWS D1.3, as applicable.
(e) Welding personnel performance qualification records and continuity records.
(f) Component manufacturers and installers written quality control program(s) that include
material control procedures, inspection procedures, and nonconformance procedures.
(g) Component manufacturers and installers quality control inspector qualifications.
D4 Quality Assurance Agency Documents
The agency responsible for quality assurance shall submit the following documents to the
authority having jurisdiction, registered design professional and owner, as applicable:
(a) Quality assurance agencys written practices for the monitoring and control of the agencys
operations. The written practice shall include:
(1) The agencys procedures for the selection and administration of inspection personnel,
describing the training, experience and examination requirements for qualification
and certification of inspection personnel.
(2) The agencys inspection procedures, including general inspection, material controls,
and visual welding inspection.
(b) Qualifications of management designated for the project.
(c) Qualification records for inspectors designated for the project.
D5 Inspection Personnel
D5.1 Quality Control Inspector
D5.1.1 A quality control inspector shall be designated as the person with overall responsibility
for quality control. It is permitted to delegate specific quality control tasks to qualified
personnel.
D5.1.2 Quality control welding inspection personnel shall be qualified in accordance with the
component manufacturers or installers quality control program, as applicable, and in
accordance with one of the following:
(a) Associate Welding Inspector (AWI) or higher as defined in AWS B5.1.
(b) Qualified by training or experience, or both, in cold-formed steel light-frame
construction component manufacturing, installation, inspection, or testing and
competent to perform inspection of the work.
D5.1.3 Quality control mechanical fastener inspection personnel shall be qualified in
accordance with the installers quality control program on the basis of training and
experience in installation of similar fasteners and shall be competent to perform
inspection of the work.

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AISI S240-15

D5.2 Quality Assurance Inspector

D5.2.1 The approved quality assurance inspector shall be designated as the person with overall
responsibility for quality assurance. The approved quality assurance inspector is permitted to
delegate specific quality assurance tasks to qualified personnel.
D5.2.2 Quality assurance welding inspection personnel shall be qualified in accordance with
the quality assurance agencys written practice and with either of the following:
(a) Welding Inspector (WI) or higher as defined in AWS B5.1, except Associate
Welding Inspectors (AWI) shall be permitted to be used under the direct
supervision of WIs or higher who are on the premises and available when weld
inspection is being conducted; or
(b) Qualified by training or experience, or both, in cold-formed steel light-frame
construction installation, inspection or testing and competent to perform inspection of
the work.
D5.2.3 Quality assurance mechanical fastener inspection personnel shall be qualified in
accordance with the quality assurance agencys written practice on the basis of training
and experience in inspection of similar fasteners.
D6 Inspection Tasks
D6.1 General
Inspection tasks and documentation for quality control and quality assurance shall be in
accordance with the tables in Sections D6.5, D6.6, D6.7, D6.8, and D6.9. These tables specify
distinct inspection tasks as follows:
(a) Observe. Observe shall mean to perform inspection of these items on an intermittent basis.
Operations that do not interfere with the ability to perform inspection of these items need not be
delayed pending these inspections. Frequency of observations shall be adequate to confirm
that the work has been performed in accordance with the applicable documents.
(b) Perform. Perform shall mean to execute these tasks prior to final acceptance for each item or
element.
(c) Document. Within the listed tasks, document shall mean the inspector shall prepare reports
or other written documentation indicating that the work has or has not been performed in
accordance with the construction documents.
D6.2 Quality Control Inspection Tasks
D6.2.1 Quality control inspection tasks shall be performed by the component manufacturers or
installers quality control inspector, as applicable, in accordance with Sections D6.6
through D6.10. Tasks in the tables in Sections D6.5 through D6.9 listed for QC shall be
those inspections performed by the quality control inspector to ensure that the work is
performed in accordance with the construction documents.
D6.2.2 Quality control inspection shall utilize the following, as applicable: construction
documents, installation drawings, shop drawings, plans, specifications or referenced standards.
D6.3 Quality Assurance Inspection Tasks
D6.3.1 Quality assurance inspection of the component assemblies shall be made at the component
manufacturers plant. The quality assurance inspector shall schedule this work to minimize
interruptions to the work of the component manufacturer.
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North American Standard For Cold-Formed Steel Structural Framing, 2015 Edition

D6.3.2 Quality assurance inspection of the cold-formed steel light-frame construction shall be
made at the project site. The contractor shall schedule this work with the quality
assurance inspector and the installer to minimize interruptions to the work of the installer.
D6.3.3 The quality assurance inspector shall review the materials test reports and
certifications listed in Section D3.2 for compliance with the construction documents.
D6.3.4 Quality assurance tasks shall be performed by the quality assurance inspector, in
accordance with Sections D6.5 through D6.9. Tasks in the tables in Sections D6.5
through D6.9 listed for QA shall be those inspections performed by the quality assurance
inspector to ensure that the work is performed in accordance with the construction
documents.
D6.3.5 Concurrent with the submittal of reports to the authority having jurisdiction, registered
design professional and owner, as applicable, the quality assurance inspector shall submit to
the contractor and the installer lists of nonconforming items.
D6.4 Coordinated Inspection
D6.4.1 Where a task is noted to be performed by both quality assurance and quality control, it
is permitted to coordinate inspection function between the quality control inspector and
quality assurance inspector so that the inspection functions are performed by only one
party when approved in advance by the owner, registered design professional, and
authority having jurisdiction.
D6.4.2 Where quality assurance tasks are performed only by the quality control inspector,
each inspection shall be documented in a report and the quality assurance inspector shall
periodically review the work of the quality control inspector at an interval acceptable to
the owner, registered design professional, and authority having jurisdiction.
D6.5 Material Verification
D6.5.1 The component manufacturers quality control inspector shall perform inspections of the
cold-formed steel structural members and connectors used in component assemblies to verify
compliance with the details shown on the shop drawings.
D6.5.2 The installers quality control inspector shall perform inspections of the cold-formed steel
structural members and connectors that are not part of a component assembly to verify
compliance with the details shown on the installation drawings.
D6.5.3 The quality assurance inspector shall perform verifications and inspections, as
applicable, to verify compliance with the construction documents and this Standard.
D6.5.4 Inspection tasks shall be in accordance with Tables D6.5-1 and D6.5-2.

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AISI S240-15

Table D6.5-1
Material Verification Tasks
Prior to Assembly or Installation
Task

Verify compliance of cold-formed steel structural members:

- Product identification (Section A5.5)

Perform

Verify compliance of connectors

Perform

Document acceptance or rejection of cold-formed steel

structural members and connectors

Not
Required 1

Perform

Documentation tasks for quality control should be as defined by the applicable quality control program of the
component manufacturer or installer.

Table D6.5-2
Material Verification Tasks
After Assembly or Installation
Task

Verify compliance of cold-formed steel structural members:

- Product identification (Section A5.5)

Perform

Verify compliance of connectors

Perform

Document acceptance or rejection of cold-formed steel

structural members and connectors

Not
Required 1

Perform

Documentation tasks for quality control should be as defined by the applicable quality control program of the
component manufacturer or installer.

D6.6 Inspection of Welding

D6.6.1 Observation of welding operations and visual inspection of in-process and
completed welds shall be the primary method to confirm that the materials, procedures
and workmanship are in conformance with the construction documents and AWS D1.3.
D6.6.2 Welding inspection tasks shall be in accordance with Tables D6.6-1, D6.6-2 and
D6.6-3.
Table D6.6-1
Inspection or Execution Tasks
Prior to Welding
Task

Welding procedure specifications available

Observe

Manufacturer certifications for welding consumables available

Observe

Material identification (type/grade)

Observe

Check welding equipment

Observe

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North American Standard For Cold-Formed Steel Structural Framing, 2015 Edition

Table D6.6-2
Inspection or Execution Tasks
During Welding
Task

Use of qualified welders

Observe

Control and handling of welding consumables

Observe

Environmental conditions (wind speed, moisture, temperature)

Observe

Welding procedure specifications followed

Observe

Table D6.6-3
Inspection or Execution Tasks
After Welding
Task

Verify compliance of welds

Perform

Welds meet visual acceptance criteria

Perform

Verify repair activities

Perform

Document acceptance or rejection of welded connections

Not
Required 1

Perform

Documentation tasks for quality control should be as defined by the applicable quality control program of the
component manufacturer or installer.

D6.7 Inspection of Mechanical Fastening

D6.7.1 Observation of mechanical fastening operations and visual inspection of in-process
and completed connections shall be the primary method to confirm that the materials,
procedures and workmanship are in conformance with the construction documents and
manufacturers installation instructions.
D6.7.2 Mechanical fastening inspection tasks shall be in accordance with Tables D6.7-1,
D6.7-2 and D6.7-3.
Table D6.7-1
Inspection or Execution Tasks
Prior to Mechanical Fastening
Task

Mechanical fastener manufacturer installation instructions

available for mechanical fasteners

Observe

Proper tools available for mechanical fastener installation

Observe

Proper storage for mechanical fasteners

Observe

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AISI S240-15

Table D6.7-2
Inspection or Execution Tasks
During Mechanical Fastening
Task

Mechanical fasteners are positioned as required

Observe

Mechanical fasteners are installed in accordance with

manufacturers instructions

Observe

Table D6.7-3
Inspection or Execution Tasks
After Mechanical Fastening
Task
A

Verify compliance of mechanical fasteners

Perform

Repair activities

Perform

Document acceptance or rejection of mechanically fastened

connections

Not
Required 1

Perform

Documentation tasks for quality control should be as defined by the applicable quality control program of the
component manufacturer or installer.

D6.8 Inspection of Cold-Formed Steel Light-Frame Construction

D6.8.1 The component manufacturers quality control inspector shall perform inspections of the
component assemblies to verify compliance with the details shown on the shop drawings.
D6.8.2 The installers quality control inspector shall perform inspections of the field-installed
cold-formed steel structural members, component assemblies and connectors to verify
compliance with the details shown on the installation drawings.
D6.8.3 The quality assurance inspector shall perform verifications and inspections, as
applicable, to verify compliance with the construction documents.
D6.8.4 Inspection tasks shall be in accordance with Table D6.8-1.
Table D6.8-1
Inspection or Execution Tasks
After Installation of Cold-Formed Steel Light-Frame Construction
Task
QC
A

Verify compliance of cold-formed steel light-frame construction

Document acceptance or rejection of cold-formed steel lightframe construction

Perform

Not
Required 1

Perform

Documentation tasks for quality control should be as defined by the applicable quality control program of the
component manufacturer or installer.

D6.9 Additional Requirements for Lateral Force-Resisting Systems

Additional inspection tasks for cold-formed steel lateral force-resisting systems shall be in
accordance with Tables D6.9-1 through D6.9-5.
Exception: The requirements in Section D6.9 are not required for cold-formed steel lateral forceresisting systems where either of the following apply:
(a) The sheathing of the shear wall is gypsum board or fiberboard.
(b) The sheathing is wood structural sheathing or steel sheet sheathing on only one side of
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North American Standard For Cold-Formed Steel Structural Framing, 2015 Edition

the shear wall or diaphragm assembly and the fastener spacing of the sheathing is more
than 4 inches (102 mm) on center (o.c.).
D6.9.1 Fit-Up of Welds
In Table D6.9-2, following performance of the inspection task for 10 welds made by a
given welder, with the welder demonstrating understanding of requirements and
possession of skills, the Perform designation of this task shall be reduced to Observe.
Table D6.9-1
Additional Inspection or Execution Tasks
Prior to Installation of Cold-Formed Steel Lateral Force-Resisting Systems
Task
QC

Verify compliance of shear wall and diaphragm sheathing,

diagonal strap bracing, and hold-downs

Document acceptance or rejection of shear wall and diaphragm

sheathing, diagonal strap bracing, and hold-downs

Perform

Not
Required 1

Perform

Documentation tasks for quality control should be as defined by the applicable quality control program of the
component manufacturer or installer.

Table D6.9-2
Additional Inspection or Execution Tasks
Prior to Welding of Cold-Formed Steel Lateral Force-Resisting Systems
Task
QC

1
2

Welder identification system 1

Observe

Fit-up of welds (alignment, gaps, condition of steel surfaces)

Perform/
Observe 2

Observe

A system maintained by the component manufacturer or installer, as applicable, by which a welder who has welded a
joint or member can be identified.
See Section D6.9.1.

Table D6.9-3
Additional Inspection or Execution Tasks
Prior to Mechanical Fastening of Cold-Formed Steel Lateral Force-Resisting Systems
Task
QC
QA
A

Proper fasteners selected

Observe

Proper installation procedure selected

Observe

Connecting elements meet applicable requirements

Observe

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AISI S240-15

Table D6.9-4
Additional Inspection or Execution Tasks
During Mechanical Fastening of Cold-Formed Steel Lateral Force-Resisting Systems
Task
QC
QA
A

For screw connections, joint brought tight (e.g., clamped) to

avoid gaps between plies

Observe

For screw connections, tool adjusted to avoid stripped and

overdriven fasteners

Observe

For post-installed connections to concrete, installation in

accordance with manufacturers instructions

Perform

Table D6.9-5
Additional Inspection or Execution Tasks
After Installation of Cold-Formed Steel Lateral Force-Resisting Systems
Task
QC

Verify compliance of cold-formed steel lateral force-resisting

system installation

Document acceptance or rejection of installation of cold-formed

steel lateral force-resisting system

Perform

Not
Required 1

Perform

Documentation tasks for quality control should be as defined by the applicable quality control program of the
component manufacturer or installer.

D7 Nonconforming Material and Workmanship

D7.1 Additional Inspections
In the event that observations determine that the materials and/or workmanship are not
in conformance with the applicable documents, additional inspections, as specified by the
quality control program or registered design professional, shall be performed to determine the
extent of non-conformance.
D7.2 Rejection of Material
D7.2.1 Identification and rejection of materials and workmanship not in conformance with
the construction documents is permitted at any time during progress of or following the
completion of the work. However, this provision shall not relieve the owner or the
inspector of the obligation for timely, in-sequence inspections.
D7.2.2 Nonconforming material and workmanship shall be brought to the immediate
attention of the contractor and the installer.
D7.2.3 Nonconforming material or workmanship shall be brought into conformance, or
made suitable for its intended purpose, as determined by the registered design
professional.

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North American Standard For Cold-Formed Steel Structural Framing, 2015 Edition

E. TRUSSES
E1 General
Cold-formed steel trusses shall be designed in accordance with the requirements of this
chapter, as applicable.
E1.1 Scope and Limits of Applicability
E1.1.1 Chapter E shall apply to design, manufacturing, quality criteria, installation and
testing as they relate to the design of cold-formed steel trusses.
E1.1.2 The responsibilities specified in Section E2 are not intended to preclude alternate
provisions as agreed upon by the parties involved.
E2 Truss Responsibilities
Truss responsibilities shall be in accordance with Section I1 of AISI S202.
E3 Loading
[Reserved]
E4 Truss Design
Except as modified or supplemented in this Standard, strength determinations shall be in
accordance with AISI S100 [CSA S136].
E4.1 Materials
Sheet steel materials utilized in steel truss construction shall comply with ASTM
A1003/A1003M Type H or ASTM A653/A653M Type SS, HSLAS, or HSLAS-F. Cold-formed
steel welded tubing utilized in steel truss construction shall comply with ASTM A500.
E4.2 Corrosion Protection
Truss members, including gusset plates, shall have corrosion protection as required in
accordance with Section A4.
E4.3 Analysis
In lieu of a rational engineering analysis to define joint flexibility, the following analysis
modeling assumptions shall be used:
(1) Chord members are continuous, except at the heel, pitch breaks, and chord splices where
members are assumed to have pinned connections.
(2) Web members are assumed to have pinned connections at each end.
Use of a specific joint stiffness other than the complete rotational freedom of a pin for a
connection is permitted if the connection is designed for the forces resulting from a structural
analysis with this specific joint stiffness.
E4.4 Member Design
E4.4.1 Properties of Sections
For C-shapes and other simple cross-section geometries, the properties of sections shall

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AISI S240-15

be determined in accordance with conventional methods of structural design rational

engineering analysis. Properties shall be based on full cross-section properties, except where
use of a reduced cross-section or effective design width is required by AISI S100 [CSA
S136]. For other cross-section geometries, properties shall be based on tests in accordance
with Appendix 2.1.
E4.4.2 Compression Chord Members
The compression chord member shall be evaluated for axial load alone using Section C4
of AISI S100 [CSA S136], bending in accordance with Section C3.1 of AISI S100 [CSA S136],
and combined axial load and bending in accordance with Section C5.2 of AISI S100 [CSA
S136].
E4.4.2.1 For axial load strength [resistance] determination, the effective length, KL, shall
be determined by rational engineering analysis, testing, or the following design
assumptions as applicable:
(a) For C-shape chord members with the x-axis as the axis of symmetry: Lx shall be
equal to the distance between panel points, and Cm shall be taken as 0.85, unless
an analysis is performed to justify another value. Where the chord member is
continuous over at least one intermediate panel point and where sheathing is
directly attached to the chord member, Kx shall be taken as 0.75. Otherwise, Kx
shall be taken as unity. As an alternative, Lx shall be the distance between
points of contraflexure with Cm and Kx taken as unity. Where sheathing is
attached to the chord member, Ly shall be equal to the distance between
sheathing connectors and Ky shall be taken as 0.75. Where purlins are attached
to the chord member, Ly shall be the distance between purlins with Ky equal to
unity. Lt shall be equal to the distance between panel points. Where the chord
member is continuous over at least one intermediate panel point between the heel
and pitch break and where sheathing is directly attached to the chord member, Kt
shall be taken as 0.75. Otherwise, Kt shall be taken as unity. As an alternate, Lt
shall be the distance between points of contraflexure with Kt taken as unity.
where
Cm =
Kt =
Kx =
Ky =
Lt =
Lx =
Ly =

End moment coefficient in interaction formula

Effective length factor for torsion
Effective length factor for buckling about x-axis
Effective length factor for buckling about y-axis
Unbraced length of compression member for torsion
Unbraced length of compression member for bending about x-axis
Unbraced length of compression member for bending about y-axis

(b) For hat-shapes with the x-axis as the axis of symmetry: Where sheathing is
attached to the chord member, Lx shall be equal to the distance between
sheathing connectors and Kx shall be taken as 0.75. Where purlins are attached
to the chord member, Lx shall be the distance between purlins with Kx equal to
unity. Ly shall be equal to the distance between panel points, and Cm shall be
taken as 0.85, unless an analysis is performed to justify another value. Where
the chord member is continuous over at least one intermediate panel point and

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North American Standard For Cold-Formed Steel Structural Framing, 2015 Edition

where sheathing is directly attached to the chord member, Ky shall be taken as

0.75. Otherwise, Ky shall be taken as unity. As an alternative, Ly shall be the
distance between points of contraflexure with Cm and Ky taken as unity. Lt
shall be equal to the distance between sheathing connectors or purlin spacing.
Where the chord member is continuous over at least one intermediate panel point
between the heel and pitch break and where sheathing is directly attached to the
chord member, Kt shall be taken as 0.75. Otherwise, Kt shall be taken as unity. As
an alternate, Lt shall be the distance between the points of contraflexure with Kt
taken as unity.
(c) For Z-shapes with the x-axis as out-of-the-plane of the truss: Lx shall be equal to
the distance between panel points, and Cm shall be taken as 0.85, unless an
analysis is performed to justify another value. Where the chord member is
continuous over at least one intermediate panel point and where sheathing is
directly attached to the chord member, Kx shall be taken as 0.75. Otherwise, Kx
shall be taken as unity. As an alternative, Lx shall be the distance between
points of contraflexure with Cm and Kx taken as unity. Where sheathing is
attached to the chord member, Ly shall be equal to the distance between
sheathing connectors and Ky shall be taken as 0.75. Where purlins are attached
to the chord member, Ly shall be the distance between purlins with Ky equal to
unity. Where the chord member depth is less than 6 inches, Lt shall be equal to
the distance between sheathing connectors or purlin spacing. For Z-shapes
where the chord member depth is greater than or equal to 6 inches, Lt shall be
equal to the distance between panel points. Where the chord member is continuous
over at least one intermediate panel point between the heel and pitch break and
where sheathing is directly attached to the chord member, Kt shall be taken as
0.75. Otherwise, Kt shall be taken as unity. As an alternative, Lt shall be equal to
the distance between points of contraflexure with Kt taken as unity.
E4.4.2.2 For bending strength [resistance] determination, the effective length, KL, shall
be determined by rational engineering analysis, testing, or the following design
assumptions as applicable:
(a) Where sheathing is attached to the compression flange, Mn = SeFy in accordance
with Section C3.1.1 of AISI S100 [CSA S136].
(b) Where purlins are attached to the compression flange between panel points, Mn =
ScFc in accordance with Section C3.1.2.1 of AISI S100 [CSA S136] with KLy and
KLt for C-shapes and Z-shapes determined in accordance with E4.4.2.1 and KLx
and KLt for hat-shapes taken as the distance between purlins.
(c) Where sheathing or purlins are attached to the tension flange and the
compression flange is laterally unbraced, Mn = ScFc in accordance with Section
C3.1.2.1 of AISI S100 [CSA S136]. For continuous span chord members, Mn in the
region of the panel point shall be determined with KLy and KLt for C-shapes and
Z-shapes determined in accordance with E4.4.2.1 and KLx and KLt for hat-shapes
taken as the distance between the panel point and the point of contraflexure, and
Cb shall be taken as unity. For simple and continuous span chord members, Mn in
the mid-span region shall be determined with the effective length taken as the

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AISI S240-15

distance between panel points and Cb shall be computed in accordance with

Section C3.1.2.1 of AISI S100 [CSA S136].
where
Cb =
Fc =
Fy =
Kt =
Kx =
Ky =
Lt =
Lx =
Ly =
Mn =
Sc =
Se =

Bending coefficient dependent on moment gradient

Critical buckling stress
Yield strength used for design
Effective length factor for torsion
Effective length factor for buckling about x-axis
Effective length factor for buckling about y-axis
Unbraced length of compression member for torsion
Unbraced length of compression member for bending about x-axis
Unbraced length of compression member for bending about y-axis
Nominal flexural strength [resistance]
Elastic section modulus of effective section calculated relative to
extreme compression fiber at Fc
Elastic section modulus of effective section calculated relative to
extreme compression fiber at Fy

E4.4.2.3 When a C-shaped section compression chord member is subject to concentrated

load at a panel point, the interaction of axial compression, bending and web crippling
shall be determined in accordance with the following:
For ASD:
P
M
R
1.49
(Eq. E4.4.2.3-1)
+
+

Pno M nxo R n

where
P
= Required compressive axial strength
Mx = Required flexural strength
R
= Required concentrated load strength
Pno = Nominal axial strength determined at f = Fy
Mnxo= Nominal flexural strength determined at f = Fy
Rn = Nominal interior one-flange web crippling strength
= 1.95
For LRFD and LSD:
P
Mx
R
+
+
1.49
Pno M nxo R n

(Eq. E4.4.2.3-2)

where
P = Required compressive axial strength [axial force of factored loads]
M x = Required flexural strength [moment of factored loads]

R =
Pno =
Mnxo=
Rn =

=
=

Required concentrated load strength [factored concentrated load]

Nominal axial strength [resistance] determined at f = Fy
Nominal flexural strength [resistance] determined at f = Fy
Nominal interior one-flange loading web crippling strength [resistance]
0.85 for LRFD
0.80 for LSD

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North American Standard For Cold-Formed Steel Structural Framing, 2015 Edition

E4.4.3 Tension Chord Members

The tension chord member shall be evaluated for axial load in accordance with Section C2
of AISI S100 [CSA S136], bending in accordance with Section C3.1 of AISI S100 [CSA S136],
and combined axial load and bending in accordance with Section C5.1 of AISI S100 [CSA
S136]. The axial load is permitted to be taken as acting through the centroid of the section.
E4.4.4 Compression Web Members
Compression web members shall be evaluated for axial load alone using Section C4 of
AISI S100 [CSA S136] and combined axial load and bending using Section C5.2 of AISI S100
[CSA S136], and the requirements of this section, as applicable.
E4.4.4.1 For a C-shaped compression web member that is attached at each end through its
web element back-to-back with the web of a C-shaped chord member and is not
subjected to applied loads between its ends, the interaction of axial compression and
out-of-plane bending shall be determined in accordance with the following
interaction equation:
For ASD:
c RP b C my RPe
(Eq. E4.4.4-1)
+
1.0
Pn
M ny y
For LRFD and LSD:
C my R Pe
RP
+
1.0
c Pn b M ny y
where

(Eq. E4.4.4-2)

L /r
L /r
R =
(Eq. E4.4.4-3)
0.22 0.6
+
88
173
L = Unbraced length of the compression web member
r = Radius of gyration of the full section about the minor axis
Pn = Nominal axial strength [resistance] based on Section C4.1 of AISI S100
[CSA S136]. Only flexural buckling need be considered.
e = Eccentricity of compression force with respect to the centroid of the full
section of the web member
P, b, c, Cmy, Mny, P , c, b and y shall be as determined in accordance
with Section C5.2.1 (ASD) or C5.2.2 (LRFD and LSD) of AISI S100 [CSA
S136].
When computing the available strength [resistance], the effective lengths, KxLx, KyLy
and KtLt, shall be taken as the distance between the centers of the members end
connection patterns.
E4.4.4.2 For other compression web members that are concentrically loaded, the axial
compression load is permitted to be taken as acting through the centroid of the
section.
E4.4.4.3 For other compression web members that are not concentrically loaded, proper
regard for eccentricity shall be considered.

E4.4.5 Tension Web Members

Tension web members shall be evaluated for axial load in accordance with Section C2 of
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AISI S240-15

AISI S100 [CSA S136]. For tension web members, which are symmetrically loaded, the axial
tension load is permitted to be taken as acting through the centroid of the section. For other
tension members that are not symmetrically loaded, proper regard for eccentricity shall be
considered.
E4.4.6 Eccentricity in Joints
E4.4.6.1 A rational engineering analysis using multiple nodes or an analysis using single
node that includes proper regard for the effects of eccentricity shall be performed.
E4.4.6.2 Chord member shear and moments in joints shall include the following
considerations:
(a) Where the web member lap length is greater than or equal to 75% of the chord
member depth, the chord member shall be investigated for combined bending and
shear in accordance with Equation C3.3.1-2 (ASD) or Equation C3.3.2-2 (LRFD
and LSD) of AISI S100 [CSA S136]. For C-shaped section trusses where screws are
used as the connector, a minimum of four screws shall be used in the web
member to chord member connection and the screws shall be uniformly distributed
in the lapped area.
(b) Where the web member lap length is less than 75% of the chord member depth, the
chord member shall be investigated for combined bending and shear in
accordance with Equation C3.3.1-1 (ASD) or C3.3.2-1 (LRFD and LSD) of AISI
S100 [CSA S136].
E4.4.6.3 Along the length of the chord member, at the mid-point between the intersecting
web members at a joint, shear shall be evaluated by Section C3.2 of AISI S100 [CSA
S136]. The shear buckling coefficient shall be based on either Equation C3.2.1-6 or
C3.2.1-7 with a taken as the smaller of the distance between the fastener groups, or
center-to-center of the web members.
E4.5 Gusset Plate Design
E4.5.1 The nominal axial compressive strength [resistance], Pn, of thin, flat gusset plates shall
be calculated as follows:
(Eq. E4.5-1)
Pn = R g btFy
where

W
Rg = 0.47 min + 0.3
L eff

=1.0
b

where

Wmin
1.5
L eff

where

Wmin
> 1.5
L eff

(Eq. E4.5-2)

= Effective width determined in accordance with Section B2.1 of AISI S100 [CSA
S136] with f=Fy, k=4 and w=Wmin
Fy = Specified minimum yield strength
t = Design thickness of gusset plate
c = 2.50 for ASD
c = 0.60 for LRFD
= 0.50 for LSD
Wmin shall be taken as the lesser of the actual gusset plate width or Whitmore section,
which shall be determined using a spread-out angle of 30 along both sides of the
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North American Standard For Cold-Formed Steel Structural Framing, 2015 Edition

connection, beginning at the first row of fasteners in the connection. Leff shall be taken as
the average length between the last rows of fasteners of adjacent truss members in the
connection.
Equation E4.5-1 shall be valid for the range of parameters listed in Table E4.5-1.
Table E4.5-1
Parameters for Equation E4.5-1
Parameter

Minimum

Maximum

Design Thickness

0.0566 inch (1.438 mm)

0.1017 inch (2.583 mm)

Design Yield Strength

Wmin / Leff Ratio

33 ksi (228 MPa)

50 ksi (345 MPa)

0.8

6.0

Two rows with two fasteners per row

n/a

Gusset Plate:

Chord Member-to-Gusset
Plate Fastener Pattern

E4.5.2 The nominal axial tensile strength [resistance] of thin, flat gusset plates shall be
calculated in accordance with the requirements of Section C2 of AISI S100 [CSA S136].
E4.6 Connection Design
E4.6.1 Fastening Methods
Fastening systems shall be specified by the truss designer. Screw, bolt, and weld
connections shall be designed in accordance with AISI S100 [CSA S136]. For connections
using other fastener types, design values shall be determined by testing in accordance with
Section F1 of AISI S100 [CSA S136].
Other fastening methods shall be in accordance with the manufacturers requirements.
E4.6.2 Coped Connections for C-Shaped Sections
E4.6.2.1 Coping is permitted at pitch break and heel connections in accordance with the
truss design and the following, as applicable:
(a) At a coped heel connection with a coped flange and a bearing stiffener having a
moment of inertia (Imin) greater than or equal to 0.161 in.4 (67,000 mm4), the
available shear strength [factored resistance] shall be calculated in accordance with
Section C3.2 of AISI S100 [CSA S136] and reduced by the following factor, R:
0.556 c 0.532d c
(Eq. E4.6.2-1)
R = 0.976
1.0

h
h
where
c
= Length of cope
dc = Depth of cope
h
= Flat width of web of section being coped
Imin = Moment of inertia determined with respect to an axis parallel to the
web of the chord member
t
= Design thickness of section being coped
(b) At a coped heel connection with a coped flange where a bearing stiffener having a
moment of inertia (Imin) less than 0.161 in.4 (67,000 mm4), the strength at the heel

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AISI S240-15

is governed by web crippling determined in accordance with Section C3.4 of

AISI S100 [CSA S136] and reduced by the following factor, R:
0.668c 0.0505d c
(Eq. E4.6.2-2)

1.0
R = 1.036
h
h
E4.6.2.2 Equations E4.6.2-1 and E4.6.2-2 shall be applicable within the following
limitations:
h/t 200,
0.10 < c/h <1.0, and
0.10 < dc/h < 0.4
E4.7 Serviceability
Serviceability requirements, as specified in AISI S100 [CSA S136], shall be determined by
the building designer or applicable building code. When computing truss deflections, it is
permitted to use the full cross-sectional area of the truss members.
E5 Quality Criteria for Steel Trusses
Section E5 applies to the manufacture of cold-formed steel trusses.
E5.1 Manufacturing Quality Criteria
The truss manufacturer shall manufacture the trusses in accordance with the final truss
design drawings, using the quality criteria required by the manufacturers quality control
program unless more stringent quality criteria are required by the owner in writing or
through the construction documents.
E5.2 Member Identification
Truss chord members and web members shall be identified in accordance with the product
identification requirements for framing members defined in Section A5.5.
E5.3 Assembly
E5.3.1 Trusses shall have steel members that are accurately cut, in accordance with the truss
design, so that the assembled truss is made by close-fitting steel members.
E5.3.2 The maximum gap between web members shall not exceed 1/2 inch (12.7 mm) unless
specified or accepted by the truss design engineer or truss designer.
E5.3.3 The location of chord members, web members, and joints shall be as specified in the
truss design.
E5.3.4 Truss dimensions which vary from the truss design shall not exceed the tolerances
shown in Table E5.8. Inaccuracies exceeding these allowable tolerances shall be
acceptable upon approval and follow-up documentation by the truss design engineer or
truss designer.
E5.3.5 Any shop modifications or repairs shall be documented by the truss design engineer
or truss designer.

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North American Standard For Cold-Formed Steel Structural Framing, 2015 Edition

Table E5.5-1
Manufacturing Tolerances for Finished Truss Units
Length1
Variance from Design Dimensions

1
2

Up to 30 feet (9.14 m)
Over 30 feet (9.14 m)

inch (12.7 mm)

inch (19.1 mm)

Height2

Variance from Design Dimensions

Up to 5 feet (1.52 m)
Over 5 feet (1.52 m)

inch (6.4 mm)

inch (12.7 mm)

Length, for manufacturing tolerance purposes, is the overall length of the truss
unit, excluding overhangs and extensions.
Height, for manufacturing tolerance purpose, is the overall height of the truss unit
measured from the top of the top chord member to the bottom of the bottom
chord member at the highest point of the truss, excluding projections above the
top chord member and below the bottom chord member, overhangs, and
extensions.

E6 Truss Installation
Section E6 applies to installation of cold-formed steel trusses.
E6.1 Installation Tolerances
E6.1.1 Straightness
Trusses shall not be installed with an overall bow or bow in any chord member or panel
which exceeds the lesser of L/200 or 2 inches (50.8 mm), where L is the length of the truss,
chord member, or panel in inches.
E6.1.2 Plumbness
Trusses shall not be installed with a variation from plumb (vertical tolerance) at any
point along the length of the truss from top to bottom which exceeds 1/50 of the depth of
the truss at that point or 2 inches (50.8 mm), whichever is less, unless trusses are specifically
designed to be installed out of plumb.
E6.1.3 Top Chord Bearing Trusses
For top chord bearing trusses, a maximum gap tolerance between the inside of the
bearing and the first diagonal or vertical web member shall be specified in the design.
E7 Test-Based Design
Tests, when required as defined below, shall be conducted under the supervision of a
registered design professional in accordance with the following:
(a) For cold-formed steel truss components (chord members and web members) for which the nominal
strength [resistance] cannot be determined in accordance with this Standard or its reference
documents, performance tests shall be performed in accordance with Appendix 2.1.
(b) For cold-formed steel truss connections for which the nominal strength [resistance] cannot be
determined in accordance with this Standard or its reference documents, performance tests
shall be performed in accordance with AISI S905.
(c) For cold-formed steel trusses for which the nominal strength [resistance] can be determined in
accordance with this Standard and its reference documents or determined on the basis of

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AISI S240-15

component performance tests in accordance with Appendix 2.1, and when it must be
demonstrated that the strength [resistance] is not less than the nominal strength [resistance]
specified in this Standard or its reference documents, confirmatory tests shall be performed
in accordance with Appendix 2.2.
(d) For cold-formed steel trusses for which the nominal strength [resistance] cannot be determined in
accordance with this Standard and its reference documents or determined on the basis of
component performance tests in accordance with Appendix 2.1, performance tests shall be
performed in accordance with Appendix 2.3.

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North American Standard For Cold-Formed Steel Structural Framing, 2015 Edition

F. TESTING
F1 General
Tests, when required to determine the strength, flexibility or stiffness of cold-formed steel
structural members or connections, shall be in accordance with approved test methods and Section
F1 of AISI S100 [CSA S136], and shall be conducted under the supervision of a design
professional.
The following test standards are permitted to be used to determine the strength, flexibility
or stiffness of cold-formed steel structural members and connections via testing:
1. AISI S901, Rotational-Lateral Stiffness Test Method for Beam-to-Panel Assemblies
2. AISI S902, Stub-Column Test Method for Effective Area of Cold-Formed Steel Columns
3. AISI S903, Standard Methods for Determination of Uniform and Local Ductility
4. AISI S904, Standard Test Methods for Determining the Tensile and Shear Strength of Screws
5. AISI S905, Test Standard for Cold-Formed Steel Connections
6. AISI S907, Test Standard for Cantilever Test Method for Cold-Formed Steel Diaphragms
7. AISI S909, Standard Test Method for Determining the Web Crippling Strength of Cold-Formed Steel
Beams
8. AISI S910, Test Method for Distortional Buckling of Cold-Formed Steel Hat-Shaped Compression
Members
9. AISI S911, Method for Flexural Testing for Cold-Formed Steel Hat-Shaped Beams
10. AISI S913, Test Standard for Hold-Downs Attached to Cold-Formed Steel Structural Framing
11. AISI S914, Test Standard for Joist Connectors Attached to Cold-Formed Steel Structural Framing
12. AISI S915, Test Standard for Through-The-Web Punchout Cold-Formed Steel Wall Stud Bridging
Connectors
F2 Truss Components and Assemblies
Tests of cold-formed steel truss components and assemblies, when required in Chapter E, shall
be in accordance with Appendix 2 or other approved test methods and Section F1 of AISI S100
[CSA S136], and shall be conducted under the supervision of a design professional.

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AISI S240-15

APPENDIX 1, CONTINUOUSLY BRACED DESIGN FOR DISTORTIONAL BUCKLING

RESISTANCE
1.1 Calculation of the nominal distortional buckling strength [resistance] in flexure in
accordance with Section C3.1.4 of AISI S100 [CSA S136] or Appendix 1 of AISI S100 [CSA
S136] is permitted to utilize the restraint provided by structural sheathing attached to the
compression flange of floor joists or ceiling joists through determination of the rotational
stiffness provided to the bending member, k of Eq. 1-1. It is also permitted to assume no
rotational restraint exists, i.e., k = 0.
1.2 Calculation of the nominal distortional buckling strength [resistance] in compression in
accordance with Section C4.2 of AISI S100 [CSA S136] or Appendix 1 of AISI S100 [CSA
S136] is permitted to utilize the restraint provided by structural sheathing attached to both
flanges of floor joists or ceiling joists through determination of the rotational stiffness
provided to the bending member, k of Eq. 1-1. It is also permitted to assume no rotational
restraint exists, i.e., k = 0.
1.3 The rotational stiffness, k, shall be determined in accordance with the following:
(Eq. 1-1)
k = (1/kw + 1/kc) -1
where
kw = Sheathing rotational restraint
= EIw/L1+EIw/L2 for interior members (joists or rafters) with structural sheathing
fastened on both sides
(Eq. 1-2)
= EIw/L1 for exterior members (joists or rafters) with structural sheathing fastened on
one side
(Eq. 1-3)
where
EIw = Sheathing bending rigidity
= Values as specified in Table 1-1(a) for plywood and OSB
= Values as specified in Table 1-1(b) for gypsum board permitted only for
serviceability calculations in accordance with Section 1.1.3 of Appendix 1 of AISI
S100
L1, L2 = One-half joist spacing to the first and second sides respectively, as illustrated in
Figure 1-1
kc = Connection rotational restraint
= Values as specified in Table 1-2 for fasteners spaced 12 in. o.c. (305 mm) or closer

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North American Standard For Cold-Formed Steel Structural Framing, 2015 Edition

Table 1-1 (a)1,2

Plywood and OSB Sheathing Bending Rigidity, EIw (lbf-in2/ft)
Span
Rating

Strength Parallel to Strength Axis

Plywood
3-ply

4-ply

5-ply

Stress Perpendicular to Strength Axis

OSB

Plywood
3-ply

4-ply

5-ply

OSB

24/0

66,000

60,000

3,600

7,900

11,000

24/16

86,000

5,200

11,500

16,000

32/16

125,000

8,100

18,000

25,000

40/20

250,000

18,000

39,500

56,000

48/24

440,000

29,500

65,000

91,500

16oc

165,000

11,000

24,000

34,000

20oc

230,000

13,000

28,500

40,500

24oc

330,000

26,000

57,000

80,500

32oc

715,000

75,000

615,000

235,000

48oc

1,265,000

160,000

350,000

495,000

Note:
1. To convert to lbf-in2/in., divide table values by 12.
To convert to N-mm2/m, multiply the table values by 9.415.
To convert to N-mm2/mm, multiply the table values by 9.415.
2. Plywood and OSB bending rigidity are obtained from APA.

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AISI S240-15

Table 1-1 (b)1

Gypsum Board Bending Rigidity
Effective Stiffness (Typical Range), EIw
Board Thickness (in.)
(mm)
0.5
(12.7)
0.625
(15.9)

EI (Lb-in2/in) of width
(N-mm2/mm)
1500 to 4000
(220,000 to 580,000)
3000 to 8000
(440,000 to 1,160,000)

Note:
1. Gypsum board bending rigidity is obtained from the Gypsum Association.

Table 1-21
Connection Rotational Restraint

T
t
kc
kc
(in.)
(lbf-in./in./rad)
(N-mm/mm/rad)
(mils)
18
0.018
78
348
27
0.027
83
367
30
0.03
84
375
33
0.033
86
384
43
0.043
94
419
54
0.054
105
468
68
0.068
123
546
97
0.097
172
766
Note:
1. Fasteners spaced 12 in. (25.4 mm) o.c. or less.

Figure 1-1 Illustration of L1 and L2 for Sheathing Rotational Restraint

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North American Standard For Cold-Formed Steel Structural Framing, 2015 Edition

APPENDIX 2, TEST METHODS FOR TRUSS COMPONENTS AND ASSEMBLIES

2.1 Component Structural Performance Load Test
2.1.1 Flexural Test
Flexural tests shall be performed to determine the positive or negative flexural strength
[resistance] of the cross-section of a truss member for static load.
2.1.1.1 Number of Test Specimens
The minimum number of test specimens shall be in accordance with Section F1 of AISI
S100 [CSA S136].
2.1.1.2 Materials
The test specimens shall be representative of those intended for use in the final
product. Mechanical properties of the steel shall be determined in accordance with Section
F3 of AISI S100 [CSA S136].
2.1.1.3 Test Apparatus
The test apparatus and procedures employed shall produce a failure consistent with
the purpose.
2.1.1.4 Load and Deflection Measuring Devices
The load measuring device or devices used shall be capable of measuring loads to an
accuracy of 2% of the ultimate load.
The deflection measuring devices, if employed, shall avoid magnification of deflection
readings due to a movement of supports during loading. When deflection measuring
systems that do not compensate for support settlement are used, measurement of support
displacement under load shall be required in order to obtain an accurate load-deflection
response. Deflection readings and measuring devices shall have an accuracy of 0.01 inches
(0.25 mm).
2.1.1.5 Loading Procedures
Load shall be applied and load measurements shall be taken. The maximum loading rate
shall not exceed a corresponding applied stress rate of 3 ksi (20.7 MPa) of gross crosssectional area per minute.
2.1.1.6 Interpretation of Test Results
Evaluation of the test results shall be made in accordance with Section F1 of AISI S100
[CSA S136].
2.1.1.7 Report
The test report shall include a description of the test specimen with drawings detailing
all pertinent dimensions. The description shall define the size, geometric type, and strength
of all test specimen components. Pertinent connector information shall include type and
size.
The measured mechanical properties (base steel thickness, yield stress, tensile strength
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AISI S240-15

and percent elongation) of the tested specimens shall be included.

The documentation shall include details of the test setup, load application, deflection
measurement locations, and drawings illustrating the test fixture.
The test report shall include the ultimate load, description of the failure mode(s), and
load-deflection curves (or the load-deflection measurements).
The report shall include certification that the test program was performed under the
direction of a registered design professional.
2.1.2 Compression Test
Compression tests shall be performed to define the compressive strength [resistance],
excluding overall buckling, of a truss member for static load in accordance with AISI S902.
Alternative tests methods shall be permitted, when accepted by the truss designer.
2.2 Full-Scale Confirmatory Load Test
2.2.1 Test Specimen
For the purpose of this test, a test specimen shall consist of a full-scale truss assembly
representative of those intended for use in the final product.
2.2.2 Number of Test Specimens
A single confirmatory load test shall meet the required minimum number of test
specimens.
2.2.3 Materials
The materials contained within the test specimen shall be representative of those intended
for use in the final product. Mechanical properties of the steel shall be determined in
accordance with Section F3 of AISI S100 [CSA S136].
2.2.4 Fabrication
Fabrication of the test specimen shall be representative of that intended for the finished
product.
2.2.5 Test Apparatus
A test shall consist of a single truss, pair of trusses, or multiple trusses.
A single truss shall be tested in either a vertical position (normal or inverted) or in a
horizontal position. A pair of trusses or multiple trusses shall be tested in a vertical position
(normal or inverted).
The self-weight of the truss shall be included in the total load applied to trusses that are
tested in a vertical position to compensate for the effect of dead loads and gravity.
Reaction supports shall provide clearance above the ground or restraining frame to allow
for normal displacements, ease of loading, instrumentation, and provide room for
observations and measurements. Supports shall have strength and stiffness to resist
deformations during tests.
Support reaction hardware shall be typical of that planned for use in the completed
structure or as required to satisfy the intent of the tests.
Lateral support shall be provided beneath a single truss when tested horizontally to keep
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North American Standard For Cold-Formed Steel Structural Framing, 2015 Edition

the test truss flat and to minimize any adverse lateral displacement caused by gravity. Lateral
support shall be provided for single, paired, or multiple trusses when tested vertically to
minimize adverse lateral displacement and prevent buckling of the assembly. Where lateral
support is used, it shall not interfere with the free in-plane displacement of the truss or truss
assembly. The components of the test truss shall not be laterally supported in a manner that
will exceed that intended in a representative installation.
When loads are applied using dead weight, such as sand, masonry units, or water, the
dead load material shall be positioned to prevent arching action.
When loads are applied using water, the water shall be compartmentalized into cells to
prevent a non-uniform load as the truss deflects.
2.2.6 Load and Deflection Measuring Devices
The load measuring device or devices used shall be capable of measuring loads to an
accuracy of 2% of the ultimate load. When multiple trusses are tested as an assembly, loadmeasuring devices shall be located beneath each truss support.
The deflection measuring devices, if employed, shall avoid magnification of deflection
readings due to a movement of supports during loading. When deflection-measuring systems
that do not compensate for support settlement are used, measurement of support
displacement under load shall be required in order to obtain an accurate load-deflection
response. Deflection readings and measuring devices shall have an accuracy of 0.01 inches
(0.25 mm).
2.2.7 Loading Procedures
Loading of the test specimens shall be achieved either using an incremental loading or a
continuous loading method.
2.2.7.1

Tests to Confirm Deflection

When a test to confirm deflection is required, the test load shall be applied up to the
maximum load for deflection limit, at which time deflections shall be measured. When
loading incrementally, each of the increments of test load shall not exceed 1/5 of the
maximum load. When using continuous loading, the applied load shall be increased
uniformly until the maximum load is reached.
When testing trusses in pairs, the deflections of two trusses at corresponding locations
are permitted to be averaged. Support displacement under load shall be measured to
obtain an accurate load-deflection response when deflection-measuring systems that do
not compensate for support settlement are used.
2.2.7.2

Tests to Confirm Available Strength [Factored Resistance] Assumptions

When a test to confirm available strength [factored resistance] is required, the test load
shall be applied up to the design load times 1.65 for ASD and the design [factored] load for
LRFD [LSD]. When loading incrementally, each of the increments of test load shall not
exceed 1/5 of the design load times 1.65 for ASD and the design [factored] load for LRFD
[LSD]. When using continuous loading, the applied load shall be increased uniformly until
the design load times 1.65 ASD or the design [factored] load for LRFD [LSD] is reached. This
load shall be held for not less than 5 minutes, and then the confirmatory test shall be
considered complete.

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AISI S240-15

2.2.8 Interpretation of Test Results

The confirmatory test shall be deemed successful if the test specimen complies with the
loading requirements in Section 2.2.7. When a test to confirm design deflections is required,
the test shall be deemed successful if the measured deflections of the test specimen do not
exceed the design (dead plus live load) deflection limit.
2.2.9 Report
The test report shall include a description of the test specimen configuration with
drawings detailing all pertinent dimensions. The description shall define the size, geometric
type, and strength of all test specimen components. Pertinent connector information shall
include type and size.
The measured mechanical properties (including base steel thickness, yield stress, tensile
strength and percent elongation) of the tested specimens shall be included.
The documentation shall include details of the test setup, load application, deflection
measurement locations, and drawings illustrating the test fixture.
The test report shall include the ultimate load, description of the failure mode(s), and
load-deflection curves (or the load-deflection measurements).
The report shall include certification that the test program was performed under the
direction of a registered design professional.
2.3 Full-Scale Structural Performance Load Test
2.3.1 Test Specimen
For the purpose of this test, a test specimen shall consist of a full-scale truss assembly
representative of those intended for use in the final product.
2.3.2 Number of Test Specimens
The minimum number of test specimens shall be in accordance with Section F1 of AISI
S100 [CSA S136].
2.3.3 Materials
The materials contained within the test specimen shall be representative of those intended
for use in the final product. Mechanical properties of the steel shall be determined in
accordance with Section F3 of AISI S100 [CSA S136].
2.3.4 Fabrication
Fabrication of the test specimen shall be representative of that intended for the finished
product.
2.3.5 Test Apparatus
A test shall consist of a single truss, pair of trusses or multiple trusses.
A single truss shall be tested in either a vertical position (normal or inverted) or in a
horizontal position. A pair of trusses or multiple trusses shall be tested in a vertical position
(normal or inverted).
The self-weight of the truss shall be included in the total load applied to trusses that are
tested in a vertical position to compensate for the effect of dead loads and gravity.
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North American Standard For Cold-Formed Steel Structural Framing, 2015 Edition

Reaction supports shall provide clearance above the ground or restraining frame to allow
for displacements, loading, instrumentation, and provide room for observations and
measurements. Supports shall have strength and stiffness to resist deformations during tests.
Support reaction hardware shall be typical of that planned for use in the completed
structure or as required to satisfy the intent of the tests.
Lateral support shall be provided beneath a single truss when tested horizontally to keep
the test truss flat and to minimize any adverse lateral displacement caused by gravity. Lateral
support shall be provided for single, paired or multiple trusses when tested vertically to
minimize adverse lateral displacement and prevent buckling of the assembly. Where lateral
support is used, it shall not interfere with the free in-plane displacement of the truss or truss
assembly. The components of the test truss shall not be laterally supported in a manner that
will exceed that intended in a representative installation.
When loads are applied using dead weight, such as sand, masonry units, or water, the
dead load material shall be positioned to prevent arching action.
When loads are applied using water, the water shall be compartmentalized into cells to
prevent a non-uniform load as the truss deflects.
2.3.6 Load and Deflection Measuring Devices
When multiple trusses are tested as an assembly, load-measuring devices shall be located
beneath each truss support. The load measuring device or devices used shall be capable of
measuring loads to an accuracy of 2% of the ultimate load.
The deflection measuring devices, if employed, shall avoid magnification of deflection
readings due to a movement of supports during loading. When deflection-measuring systems
that do not compensate for support settlement are used, measurement of support
displacement under load shall be required in order to obtain an accurate load-deflection
response. Deflection readings and measuring devices shall have an accuracy of 0.01 inches
(0.25 mm).
2.3.7 Loading Procedures
Loading of the test specimens shall be achieved using either an incremental or a
continuous loading method.
When loading incrementally, each of the increments of test load shall not exceed 1/5 of
the estimated ultimate load. If structural failure has not occurred at the estimated ultimate
load, additional load is to be applied in the same increments until failure occurs.
When using continuous loading, the applied load shall be increased uniformly until
structural failure occurs.
Deflection readings shall be recorded at each load increment or continuously. When
testing trusses in pairs, the deflections of two trusses at corresponding locations are permitted
to be averaged. Support displacement under load shall be measured to obtain an accurate
load-deflection response when deflection-measuring systems that do not compensate for
support settlement are used.
For incremental loading, the ultimate load shall be the load level before failure. For
continuous loading, the ultimate load shall be the load at failure.
2.3.8 Interpretation of Test Results
The performance test is permitted to be used to determine the available strength [factored

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AISI S240-15

resistance] for the truss. For ASD, the available strength of the truss shall be the nominal strength
divided by the safety factor; and for LRFD [LSD], the available strength [factored resistance] of the
truss shall be the nominal strength [resistance] multiplied by the resistance factor. The nominal
strength [resistance] of the truss is permitted to be taken as the average of the ultimate loads of
the tested specimens. The resistance factor or safety factor for the performance test shall be
determined in accordance with Section F1 of AISI S100 [CSA S136].
2.3.9 Report
The test report shall include a description of the test specimen configuration with
drawings detailing all pertinent dimensions. The description shall define the size, geometric
type, and strength of all test specimen components. Pertinent connector information shall
include type and size.
The measured mechanical properties (including base steel thickness, yield stress, tensile
strength and percent elongation) of the tested specimens shall be included.
The documentation shall include details of the test setup, load application, deflection
measurement locations, and drawings illustrating the test fixture.
The test report shall include the ultimate load, description of the failure mode(s), and
load-deflection curves (or the load-deflection measurements).
The report shall include certification that the test program was performed under the
direction of a registered design professional.

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AISI S240-15-C

AISI STANDARD
Commentary on the
North American Standard for
Cold-Formed Steel
Structural Framing

2015 Edition

AISI S240-15-C

DISCLAIMER
The material contained herein has been developed by the American Iron and Steel Institute
(AISI) Committee on Framing Standards. The Committee has made a diligent effort to present
accurate, reliable, and useful information on cold-formed steel framing design and installation.
The Committee acknowledges and is grateful for the contributions of the numerous researchers,
engineers, and others who have contributed to the body of knowledge on the subject. Specific
references are included in this Commentary.
With anticipated improvements in understanding of the behavior of cold-formed steel
framing and the continuing development of new technology, this material will become dated. It
is anticipated that AISI will publish updates of this material as new information becomes
available, but this cannot be guaranteed.
The materials set forth herein are for general purposes only. They are not a substitute for
competent professional advice. Application of this information to a specific project should be
reviewed by a design professional. Indeed, in many jurisdictions, such review is required by law.
Anyone making use of the information set forth herein does so at their own risk and assumes
any and all liability arising therefrom.

1st Printing December 2015

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Commentary on the North American Standard For Cold-Formed Steel Structural Framing, 2015 Edition

iii

PREFACE
This Commentary is intended to facilitate the use and provide an understanding of the
background of AISI S240, North American Standard for Cold-Formed Steel Structural Framing. The
Commentary illustrates the substance and limitations of the various provisions of the Standard.
In the Commentary, sections are identified by the same notation as used in the Standard.
Words that are italicized are defined in AISI S240. Terms included in square brackets are
specific to Limit States Design terminology.

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AISI S240-15-C

This Page is Intentionally Left Blank.

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Commentary on the North American Standard For Cold-Formed Steel Structural Framing, 2015 Edition

TABLE OF CONTENTS
COMMENTARY ON THE NORTH AMERICAN STANDARD
FOR COLD-FORMED STEEL STRUCTURAL FRAMING
Disclaimer ................................................................................................................................................... ii
Preface......................................................................................................................................................... iii
COMMENTARY ON THE NORTH AMERICAN STANDARD FOR COLD-FORMED STEEL STRUCTURAL
FRAMING ......................................................................................................................................... 1
A. GENERAL ......................................................................................................................................... 1
A1 Scope...................................................................................................................................................... 1
A2 Definitions ............................................................................................................................................ 2
A2.1 Terms .............................................................................................................................................. 2
A3 Material ................................................................................................................................................. 4
A4 Corrosion Protection ........................................................................................................................... 4
A5 Products ................................................................................................................................................ 5
A5.2 Minimum Flange Width .............................................................................................................. 6
B DESIGN ............................................................................................................................................ 7
B1 General .................................................................................................................................................. 7
B1.1 Loads and Load Combinations................................................................................................... 7
B1.1.1 Live Load Reduction on Wall Studs .............................................................................. 7
B1.1.2 Wind Loading Considerations in the United States and Mexico .............................. 7
B1.2 Design Basis................................................................................................................................... 8
B1.2.1 Floor Joists, Ceiling Joists and Roof Rafters ................................................................. 8
B1.2.2 Wall Studs ......................................................................................................................... 8
B1.2.3 In-Line Framing................................................................................................................ 9
B1.2.5.2 Principles of Mechanics .................................................................................... 10
B1.3 Built-Up Sections ........................................................................................................................ 10
B1.5 Connection Design ..................................................................................................................... 11
B1.5.1 Screw Connections ......................................................................................................... 11
B1.5.1.1 Steel-to-Steel Screws......................................................................................... 11
B1.5.1.3 Spacing and Edge Distance ............................................................................. 12
B1.5.1.4 Gypsum Board .................................................................................................. 12
B1.5.2 Welded Connections...................................................................................................... 13
B1.5.3 Bolts.................................................................................................................................. 13
B1.5.4 Power-Actuated Fasteners ............................................................................................ 13
B1.5.5 Other Connectors ........................................................................................................... 13
B2 Floor and Ceiling Framing ............................................................................................................... 13
B2.5 Bearing Stiffeners........................................................................................................................ 13
B2.6 Bracing Design ............................................................................................................................ 13
B3 Wall Framing...................................................................................................................................... 13
B3.2 Wall Stud Design ........................................................................................................................ 13
B3.2.1 Axial Load ....................................................................................................................... 13
B3.2.5 Web Crippling ................................................................................................................ 16
B3.2.5.1 Stud-to-Track Connection for C-Section Studs ............................................. 16
B3.2.5.2 Deflection Track Connection for C-Section Studs......................................... 18
B3.3 Header Design ............................................................................................................................ 19
B3.3.1 Back-to-Back Headers.................................................................................................... 19
B3.3.2 Box Headers .................................................................................................................... 19
B3.3.3 Double L-Headers .......................................................................................................... 20
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AISI S240-15-C

B3.3.3.1.1 Gravity Loading ................................................................................... 21

B3.3.3.1.2 Uplift Loading ...................................................................................... 21
B3.3.4 Single L-Headers ............................................................................................................ 21
B3.3.5 Inverted L-Header Assemblies .................................................................................... 22
B3.4 Bracing ......................................................................................................................................... 23
B3.4.1 Intermediate Brace Design............................................................................................ 23
B3.5 Serviceability ............................................................................................................................... 23
B4 Roofing Framing ................................................................................................................................ 23
B4.5 Bracing Design ............................................................................................................................ 23
B5 Lateral Force-Resisting Systems ...................................................................................................... 23
B5.2 Shear Wall Design ...................................................................................................................... 23
B5.2.1 General ............................................................................................................................ 24
B5.2.2 Nominal Strength [Resistance]..................................................................................... 25
B5.2.2.1 Type I Shear Walls............................................................................................. 25
B5.2.2.2 Type II Shear Walls ........................................................................................... 28
B5.2.3 Available Strength [Factored Resistance] ................................................................... 29
B5.2.5 Design Deflection ........................................................................................................... 29
B5.3 Strap Braced Wall Design .......................................................................................................... 30
B5.4 Diaphragm Design ..................................................................................................................... 31
B5.4.1 General ............................................................................................................................ 31
B5.4.2 Nominal Strength ........................................................................................................... 31
B5.4.4 Design Deflection ........................................................................................................... 32
B5.4.5 Beam Diaphragm Tests for Non-Steel Sheathed Assemblies .................................. 32
C. INSTALLATION ...............................................................................................................................34
C2 Material Condition ............................................................................................................................ 34
C2.1 Web Holes.................................................................................................................................... 34
C2.2 Cutting and Patching ................................................................................................................. 34
C2.3 Splicing......................................................................................................................................... 34
C3 Structural Framing ............................................................................................................................ 34
C3.1 Foundation .................................................................................................................................. 34
C3.2 Ground Contact .......................................................................................................................... 34
C3.3 Floors ............................................................................................................................................ 35
C3.4 Walls ............................................................................................................................................. 35
C3.4.1 Straightness, Plumbness and Levelness ..................................................................... 35
C3.4.3 Stud-to-Track Connection ............................................................................................. 35
C3.5 Roofs and Ceilings...................................................................................................................... 36
C3.6 Lateral Force-Resisting Systems ............................................................................................... 36
C4 Connections ........................................................................................................................................ 37
C4.1 Screw Connections ..................................................................................................................... 37
C4.1.2 Installation ...................................................................................................................... 37
C4.1.3 Stripped Screws .............................................................................................................. 37
C4.2 Welded Connections .................................................................................................................. 37
C5 Miscellaneous ..................................................................................................................................... 37
C5.1 Utilities ......................................................................................................................................... 37
C5.1.1 Holes ................................................................................................................................ 37
C5.1.2 Plumbing ......................................................................................................................... 38
C5.1.3 Electrical .......................................................................................................................... 38
C5.2 Insulation ..................................................................................................................................... 38

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Commentary on the North American Standard For Cold-Formed Steel Structural Framing, 2015 Edition

vii

D. QUALITY CONTROL AND QUALITY ASSURANCE ...........................................................................39

D1 General ................................................................................................................................................ 39
D1.1 Scope and Limits of Applicability ............................................................................................ 39
D1.2 Responsibilities ........................................................................................................................... 40
D2 Quality Control Programs ................................................................................................................ 40
D3 Quality Control Documents ............................................................................................................. 41
D3.1 Documents to be Submitted ...................................................................................................... 41
D3.2 Available Documents ................................................................................................................. 41
D5 Inspection Personnel ......................................................................................................................... 42
D5.1 Quality Control Inspector.......................................................................................................... 42
D5.2 Quality Assurance Inspector..................................................................................................... 42
D6 Inspection Tasks................................................................................................................................. 42
D6.1 General ......................................................................................................................................... 42
D6.2 Quality Control Inspection Tasks............................................................................................. 42
D6.3 Quality Assurance Inspection Tasks........................................................................................ 43
D6.4 Coordinated Inspection ............................................................................................................. 43
D6.5 Material Verification .................................................................................................................. 43
D6.6 Inspection of Welding ................................................................................................................ 43
D6.7 Inspection of Mechanical Fastening......................................................................................... 43
D6.8 Inspection of Cold-Formed Steel Light-Frame Construction ............................................... 43
D6.9 Additional Requirements for Lateral Force-Resisting Systems ........................................... 43
E. TRUSSES........................................................................................................................................45
E1 General ................................................................................................................................................ 45
E1.1 Scope and Limits of Applicability ............................................................................................ 45
E2 Truss Responsibilities ....................................................................................................................... 45
E3 Loading ............................................................................................................................................... 45
E4 Truss Design ....................................................................................................................................... 45
E4.3 Analysis........................................................................................................................................ 45
E4.4 Member Design........................................................................................................................... 45
E4.4.1 Properties of Sections .................................................................................................... 45
E4.4.2 Compression Chord Members ..................................................................................... 46
E4.4.3 Tension Chord Members .............................................................................................. 47
E4.4.4 Compression Web Members ........................................................................................ 47
E4.4.5 Tension Web Members.................................................................................................. 48
E4.4.6 Eccentricity in Joints ...................................................................................................... 48
E4.5 Gusset Plate Design .................................................................................................................... 49
E4.6 Connection Design ..................................................................................................................... 51
E4.6.1 Fastening Methods......................................................................................................... 51
E4.6.2 Coped Connections for C-Shaped Sections ................................................................ 52
E4.7 Serviceability ............................................................................................................................... 53
E5 Quality Criteria for Steel Trusses .................................................................................................... 53
E6 Truss Installation ............................................................................................................................... 54
E6.1.1 Straightness ..................................................................................................................... 54
E6.1.2 Plumbness ....................................................................................................................... 54
E7 Test-Based Design ............................................................................................................................. 54
F. TESTING .........................................................................................................................................55
F1 General ................................................................................................................................................ 55
F2 Truss Components and Assemblies ................................................................................................ 55

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viii

AISI S240-15-C

APPENDIX 1, CONTINUOUSLY BRACED DESIGN FOR DISTORTIONAL BUCKLING RESISTANCE.....56

APPENDIX 2, TEST METHODS FOR TRUSS COMPONENTS AND ASSEMBLIES ................................57
2.1 Component Structural Performance Load Test............................................................................. 57
2.2 Full-Scale Confirmatory Load Test ................................................................................................. 57
2.3 Full-Scale Structural Performance Load Test ................................................................................ 58
REFERENCES.......................................................................................................................................59

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Commentary on the North American Standard For Cold-Formed Steel Structural Framing, 2015 Edition

COMMENTARY ON THE
NORTH AMERICAN STANDARD FOR
COLD-FORMED STEEL STRUCTURAL FRAMING
A. GENERAL
In 2015, the following AISI cold-formed steel framing standards were consolidated into a
single standard, AISI S240 (AISI, 2015a):
AISI S200, North American Standard for Cold-Formed Steel FramingGeneral Provisions
(AISI, 2012b)
AISI S210, North American Standard for Cold-Formed Steel FramingFloor and Roof System
Design (AISI, 2012d)
AISI S211, North American Standard for Cold-Formed Steel FramingWall Stud Design
(AISI, 2012e)
AISI S212, North American Standard for Cold-Formed Steel FramingHeader Design (AISI,
2012f)
AISI S213, North American Standard for Cold-Formed Steel FramingLateral Design (AISI,
2012g)
AISI S214, North American Standard for Cold-Formed Steel FramingTruss Design (AISI,
2012i)
In 2015, AISI S400, North American Standard for Seismic Design of Cold-Formed Steel Structural
Systems (AISI, 2015b) was developed. Modifications were made to align the provisions of AISI
S240 with AISI S400, as follows:
The applicability of AISI S240 for seismic design was limited to applications where
specific seismic detailing is not required.
Definitions no longer needed in AISI S240 were removed and remaining definitions
were revised, if needed, for consistency with AISI S400.
Seismic-specific tables for nominal shear strength [resistance] were deleted.
Seismic-specific safety factors and resistance factors were deleted.
Other seismic-specific requirements were removed, as appropriate, and remaining
requirements were generalized for applicability to wind, seismic or other lateral loads.
A1 Scope
AISI S240 applies to the design and installation of structural members utilized in cold-formed
steel light-frame construction applications and other structures. It applies to floor, wall and roof
systems, lateral force-resisting systems and trusses. However, cold-formed steel structural members
and connections in seismic force-resisting systems must be designed in accordance with the
additional provisions of AISI S400 where increased seismic performance is required.
The Standard is intended to serve as a supplement to AISI S100 [CSA S136] (AISI, 2012a;
CSA, 2012).
Design provisions related to nonstructural members can be found in AISI S220, North
American Standard for Cold-Formed Steel Framing-Nonstructural Members (AISI, 2011b). However,
the use of AISI S240 for the design of nonstructural members is permitted, since the requirements
specified in AISI S240 for structural members are equivalent or more stringent than the
requirements specified in AISI S220 for nonstructural members.
In 2015, the provision that the Standard applies to applications where the specified
minimum base steel thickness is not greater than 0.1180 inches (2.997 mm) was replaced with the

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AISI S240-15-C

provision that the Standard applies to light-frame construction applications, and a definition for
the term light- frame construction was added to the Standard. Cold-formed steel structural members
for light-frame construction applications are available in a variety of thicknesses. Standard
thicknesses for cold-formed steel structural members are defined in AISI S201 (AISI, 2012c).
A2 Definitions
A2.1 Terms
Codes and standards by their nature are technical, and as such specific words and
phrases can change the intent of the provisions if not properly defined. As a result, it is
necessary to establish a common platform by clearly stating the meaning of specific terms for
the purpose of this Standard and other standards that reference it.
In the Standard, blocking is defined to transfer shear force or stabilize members. Figures CA2-1 and C-A2-2 show examples of how track or stud members are used as blocking in various
assemblies.

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Commentary on the North American Standard For Cold-Formed Steel Structural Framing, 2015 Edition

Figure C-A2-1 Application of Stud Track Blocking

Figure C-A2-2 Application of Joist Blocking

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AISI S240-15-C

A3 Material
The sheet steel approved for use with this Standard for structural members must comply with
ASTM A1003/A1003M (ASTM, 2015), except where specifically noted otherwise. ASTM
A1003/1003M covers the chemical, mechanical and coating requirements for steel sheet used in
the manufacture of cold-formed steel framing members such as studs, joists, and tracks.
ASTM A1003/1003M is a standard that was developed in order to incorporate requirements
for metallic-coated, painted metallic-coated, or painted nonmetallic-coated steel sheet used for
cold-formed steel framing members into a single standard. Mechanical properties defined in
ASTM A1003/A1003M are minimum requirements. For example, the minimum yield strength of
Type H or L 33 [NS230] steel is 33 ksi [230 MPa]; material with higher yield strength is permitted,
but 33 ksi [230 MPa] is the design yield strength. Additionally, according to the ASTM
A1003/1003M standard, Structural Grade Types H and L steel are intended for structural
members and nonstructural Grade Type NS steel is intended for nonstructural members. It is noted
that additional country-specific limitations for curtain wall studs are provided in AISI S100 [CSA
S136], Section A2.3.1a, Appendix A or B.
A4 Corrosion Protection
The minimum coating designations listed in Standard Table A4-1 assume normal exposure
and construction practices. Other types of coatings that provide equal or better corrosion
protection may also be acceptable. When more severe exposure conditions are probable,
consideration should be given to specifying heavier coating weight [mass].
The minimum coating specified by this Standard assumes normal exposure conditions that
are defined as having the framing members enclosed within a building envelope or wall
assembly within a controlled environment. When more severe exposure conditions are
probable, such as industrial atmospheres and marine atmospheres, consideration should be
given to specifying a heavier coating. Coating is specified by weight or mass.
This Standard does not require the edges of metallic-coated cold-formed steel framing
members (shop or field cut in accordance with Standard Section C2.2, punched or drilled) to be
touched up with zinc-rich paint, which is able to galvanically protect steel. When base steel is
exposed, such as at a cut or scratch, the steel is cathodically protected by the sacrificial corrosion
of the zinc coating, because zinc is more electronegative (more reactive) than steel in the
galvanic series. A zinc coating will not be undercut because the steel cannot corrode when
adjacent to the zinc coating. Therefore, any exposure of the underlying steel at an edge or
scratch will not result in corrosion of the steel away from the edge or scratch and thus will not
affect the performance of the coating or the steel structure (CFSEI, 2007a).
It is noted that ASTM A1004/A1004M (ASTM, 2014b) covers procedures for establishing the
acceptability of steel sheet for use as cold-formed steel framing members. This practice is to be
used to assess the corrosion resistance of different coatings on steel sheet in a laboratory test. It
is not intended to be used as an application performance standard for the cold-formed steel
framing, but is to be used to evaluate coatings under consideration for addition to ASTM
A1003/A1003M (ASTM, 2015).
Direct contact with dissimilar metals (e.g., copper, brass, etc.) should be avoided in order to
prevent unwanted galvanic action from occurring. Methods for preventing the contact from
occurring may be through the use of nonconductive and noncorrosive grommets at web
penetrations or through the use of non-metallic brackets (a.k.a. isolators) fastened to hold the
dissimilar metal building products (e.g. piping) away from the cold-formed steel framing. In 2006,
a change was made to this Standard allowing the use of dissimilar metals in contact with coldThis document is copyrighted by AISI. Any redistribution is prohibited.

Commentary on the North American Standard For Cold-Formed Steel Structural Framing, 2015 Edition

formed steel framing, provided the specific application is approved. It was recognized that
dissimilar metals in contact with cold-formed steel framing might not always be a problem. For
example, there are no galvanic concerns where there is no moisture. A special case of dissimilar
metals occurs in Canada where, for certain climatic conditions and building heights, the use of
stainless steel brick ties is required. When these ties are connected to steel stud backup, contact
between dissimilar metals can occur. For guidance on this dissimilar metals issue, refer to the
Canadian standard CAN/CSA-A370-14, Connectors for Masonry (CSA, 2014).
When there is direct contact of cold-formed steel framing with pressure-treated wood, the
treated wood, cold-formed steel framing, connector and/or fastener manufacturers should be
contacted for recommendations. Methods that should be considered may include specifying a
less corrosive pressure treatment (sodium borate, organic preservative systems, etc.), isolating
the cold-formed steel and wood components, or changing details to avoid use of pressure-treated
wood altogether.
Design professionals should take into account both the initial contact with wet or damp
building materials, as well as the potential for those materials to absorb water during the
buildings life, as both circumstances may accelerate corrosion.
In 2007, the Cold-Formed Steel Engineers Institute updated the 2004 AISI document,
entitled Durability of Cold-Formed Steel Framing Members (CFSEI, 2007a), to give engineers,
architects, builders and homeowners a better understanding of how galvanizing (zinc and zinc
alloy coatings) provides long-term corrosion protection to cold-formed steel framing members.
Additional information can be obtained from the American Galvanizers Association publication
entitled Hot Dip Galvanizing For Corrosion ProtectionA Specifiers Guide (AGA, 2012) and the
Cold-Formed Steel Engineers Institutes publication entitled Corrosion Protection for Cold-Formed
Steel Framing in Coastal Areas (CFSEI, 2007b).
A5 Products
AISI S100 [CSA S136], (AISI, 2012a; CSA, 2012) permits the minimum delivered base steel
thickness (exclusive of any coatings) of a cold-formed steel member to be 95% of the design
thickness. This Standard, therefore, specifies the minimum base steel thickness that complies with
AISI S100 [CSA S136]. The thickness designations are consistent with standard industry
practice, as published in AISI S201 (AISI, 2012c). It is recommended that thickness
measurements be taken in the middle of the flat of the flange or web of the cross-section.
Section A5.3 has adopted a standard designator system for identifying cold-formed steel
framing members. The intent for using a standard designator system was to overcome the
varied designators that were produced by each individual manufacturer. In addition, the
designator is used to identify not only a specific cold-formed steel framing member, but also to
identify the section properties of that same member through the use of the manufacturers
product technical information documents.

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AISI S240-15-C

The following presents an example of the standard designator for a cold-formed steel stud:
350S162-33 represents a member with the following:

350S162-33
33 for 33 mil (0.0329 inch) (0.836mm) designation thickness
162 for 1.625 inch (41.3 mm) flange width
S for stud or joist
350 for 3.50 inch (89.9 mm) web depth
In 2011, as part of an exercise to synchronize all relevant codes and specifications, the
minimum tolerances for the manufacture of cold-formed steel framing members were included in
the AISI framing standards. The minimum tolerances for the manufacture of structural members
can be found in Section A5.4. In 2014, manufacturing tolerances for stiffening lip length and
flange width were also added. The revisions are consistent with ASTM C955 (ASTM, 2011c). The
minimum tolerances for the manufacture of nonstructural members can be found in AISI S220
(AISI, 2015). The manufacturing tolerances for length, web width, camber, bow, twist, etc. of
framing members are consistent with ASTM C955, ASTM C645 (ASTM, 2011b), and
manufacturers certification programs.
To aid in shop and field verification, all framing members are to carry a product
identification to indicate conformance with the minimum base steel thickness, coating
designation, minimum yield strength, and manufacturers name.
In 2011, color coding of individual framing members or groups of like members were
removed from the AISI framing standards with consideration that the color coding approach
could cause confusion in differentiating between structural and nonstructural members of the
same thickness. Further, color coding is optional and the criterion, if needed, exists in a nonmandatory Appendix of ASTM C645.
A5.2 Minimum Flange Width
In 2012, as part of an exercise to synchronize all relevant codes and specifications, the
provisions for minimum flange width were added to the AISI framing standards, and were
consistent with ASTM C645 (ASTM, 2011b) and ASTM C955 (ASTM, 2011c). The minimum
flange width for C-shape members was included in the Standard to accommodate a butt joint
of sheathing. The minimum flange width for track members was included in the Standard to
accommodate an edge joint of sheathing.

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Commentary on the North American Standard For Cold-Formed Steel Structural Framing, 2015 Edition

B DESIGN
B1 General
B1.1 Loads and Load Combinations
Currently, ASCE 7 (ASCE, 2013) has no geographical-based information on Mexico.
Therefore, users with projects in Mexico should work with the appropriate authority having
jurisdiction to determine appropriate loads and load combinations that are consistent with the
assumptions and rationale used by ASCE 7.
In 2009, the words with no axial loads were deleted to clarify that the intent is to
evaluate deflections for bending of the wall stud alone when subjected to the Components
and Cladding (C&C) wind loads.
B1.1.1 Live Load Reduction on Wall Studs
Since some building codes allow designers to reduce floor live load as a function of
area of floor supported by gravity load-bearing members, a requirement was added in
2009 to clarify appropriate application of area live load reduction for the design of
individual structural members in load-bearing wall framing, including vertical members
such as studs or columns and horizontal members such as headers or beams within a wall
assembly. The floor area (from one or more floors) contributing load to a wall framing
member should be determined in a manner consistent with engineering mechanics.
B1.1.2 Wind Loading Considerations in the United States and Mexico
Because a wall stud subject to combined bending and axial load resists wind loads
imposed on two surfaces, the member can be analyzed based on Main Wind Force
Resisting System (MWFRS) wind loads. For bending alone, the wall stud experiences wind
from only one surface and therefore must be analyzed for Components and Cladding
(C&C) wind loads.
Section 1609.6.2.3 of the International Building Code (ICC, 2003) states that:
Members that act as both part of the main force resisting system and as components and
cladding shall be designed for each separate load case.
Discussion in the Southern Standard Building Code Commentary (SBCCI, 1999) sheds
light on a reasonable approach to the design of wall studs for wind resistance, stating that:
Some elements of a building will function as part of the main wind force resisting system and
components and cladding also. Such members include but not limited to roof panels, rafters, and
wall studs. These elements are required to be designed using the loads that would occur by
considering the element as part main wind force resisting system, and also separately checked or
designed for loads that would occur by considering the element as component and cladding. The
use of this section can be demonstrated by considering, for example, the design of a wall stud.
When designing the stud for main wind force resisting system loads, all loads such as bending
from the lateral force with the wind on the wall in addition to any uplift in combinations with
the dead load of the roof or a story above induced by the simultaneous action of roof forces
should be considered together. When designing the stud for component and cladding loads, only
the bending resulting from the wind force normal to the stud and the dead load associated with
that member should be considered. The member should be sized according to the more critical
loading condition.

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AISI S240-15-C

The wood industry has also investigated this condition and has adopted a similar
policy as shown in the Wood Frame Construction Manual (AFPA, 1995), where Section 2.4
states that:
Studs tables are based upon bending stresses induces by C&C Loads. The bending stresses are
computed independent of axial stresses. In addition, the case in which bending stresses from
MWFRS loads act in combination with axial stresses from wind and gravity loads have been
analyzed. For buildings limited to the conditions in the WFCM-SBC, the C&C loads control
stud design.
The commentary to Appendix C of ASCE 7 (ASCE, 2006) provides some guidance on
the selection of loads for checking the serviceability limit state of buildings and their
components, where Section B1.2 states in part:
Use of factored wind load in checking serviceability is excessively conservative. The load
combination with an annual probability of 0.05 of being exceeded, which can be used in checking
short-term effects, is D + 0.5L + 0.7W.
Thus, using 70% of the wind load from Components and Cladding for checking
deflections should conservatively satisfy the above. In 2012, IBC Table 1604.3, Footnote f
recommended that 42% of the wind load be used for checking deflections. The 2012 IBC is
based on ASCE 7-10 and the ASD wind load factor of 0.6W is used to arrive at a service
load pressure; thus, 0.7 0.6 = 0.42.
AISC Design Guide No. 3 (Fisher and West, 1990) also recommends reduced wind
loads when checking the serviceability of cladding based upon a 10-year return period or
75 percent of the 50-year wind pressure.
B1.2 Design Basis
The strength determinations required by this Standard are to be in accordance with AISI
S100 [CSA S136], (AISI, 2012a; CSA, 2012). For design guidance on the application of AISI
S100 [CSA S136] to typical cold-formed steel construction, refer to Design Guide for Cold-Formed
Steel Framing (AISI, 2007b) and Cold-Formed Steel Design (Yu and LaBoube, 2010).
B1.2.1 Floor Joists, Ceiling Joists and Roof Rafters
The Standard permits the design of floor joists, ceiling joists and roof rafters to be based
on either a discretely braced design in which discrete braces are provided along the
members length, or based on a continuously braced design in which attached sheathing or
deck are attached in accordance with the Standard.
The continuously braced design provisions of the Standard are limited to floor joists,
ceiling joists and roof rafters with dimensions and properties that are within the range of
standard products, as defined by AISI S201 (AISI, 2012c). This limitation was deemed
appropriate due to the availability of research and field experience with such members.
B1.2.2 Wall Studs
The 2007 edition of AISI S100 (AISI, 2007a) added new design provisions for
considering distortional buckling of cold-formed steel members in bending (Section C3.1.4 of
AISI S100) and compression (Section C4.2 of AISI S100). Commentary to AISI S100
provides detailed technical information on distortional buckling. In 2009, distortional
buckling was introduced in this Standard, and separate provisions provided for discretely
braced design and continuously braced design. Discrete braces must restrict rotation at the
web/flange juncture. This may be accomplished with sufficiently stiff blocking to restrict
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Commentary on the North American Standard For Cold-Formed Steel Structural Framing, 2015 Edition

rotations in the web, with strap across a series of members lacing from compression flange of
one member to the tension flange of the next member and continuing, or with other
systems engineering judgment is required. Provisions for continuously braced design for
distortional buckling are provided in Section B2.6.
The Standard permits the design of wall studs to be based on either an all steel design
in which discrete braces are provided along the members length, or based on a sheathing
braced design. Because load-bearing wall studs used in multi-story construction may go
unsheathed for an extended period of time during construction, it is uncommon to use a
sheathing braced design approach. It is permitted by this Standard to use sheathing
attached to both flanges, or to use a combination of sheathing attached to one flange and
discrete bracing stabilizing the other flange. When the curtain wall stud has sheathing only
on one flange and discrete bracing on the other flange, the nominal flexural strength
[resistance] is determined using the provisions of AISI S100 Section C3.1. When sheathing is
attached to the compression flange, the lateral-torsional buckling does not need to be
considered. Otherwise, the lateral-torsional buckling should be considered in accordance
with AISI S100 Section C3.1.2. Distortional buckling should be considered whether or not
the sheathing is attached to the compression flange. In 2015, the maximum discrete bracing
spacing of 8 ft (2.44 m) on center is required based on design experience and common
practice for flexural members such as curtain wall studs.
The Standard stipulates that when sheathing braced design is used, the wall stud shall
be evaluated without the sheathing bracing for the dead loads and loads that may occur
during construction, or in the event that the sheathing has been removed or has
accidentally become ineffective. In 2014, the LRFD load combination for the United States
and Mexico was taken from ASCE 7 (ASCE, 2006) for special event loading conditions.
Although the design approach for sheathing braced design is based upon engineering
principles, the Standard limits the sheathing braced design to wall stud assemblies,
assuming that identical sheathing is attached to both sides of the wall stud. This limit
recognizes that identical sheathing will aid in minimizing the twisting of the section. If
only single-sided sheathing is used, additional twisting of the section will occur, thus
placing a greater demand on the sheathing; therefore, the stud must be designed and
braced as an all steel assembly.
The provision that wall studs with sheathing attached to both sides that is not identical
shall be permitted to be designed based on the assumption that the weaker of the two
sheathings is attached to both sides is based on engineering judgment. Determination of
which of the two sheathings is weaker shall consider the sheathing strength, sheathing
stiffness and sheathing-to-wall stud connection capacity, as applicable.
B1.2.3 In-Line Framing
In-line framing is the preferred and most commonly used framing method. The
advantage of in-line framing is that it provides a direct load path for transfer of forces from
joists to studs. The Standard stipulates maximum framing alignment to minimize secondary
moments on the framing members. Weak axis bending strength of track is minimal, and
therefore the track cannot function as a load transfer member. In the absence of in-line
framing, a load distribution member, such as a structural track, may be required for this
force transfer.
Industry practice has accepted in-line framing to mean that the joist, rafter, truss and
structural wall stud framing would be aligned so that the center line (mid-width) is within

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AISI S240-15-C

inch (19 mm) of the center line (mid-width) of the load-bearing members beneath.
However, the inch allowable offset creates the possibility for a misalignment in the load
path from an upper story load bearing stud wall, through a joist with a bearing stiffener, and
onto a load-bearing stud or foundation wall below. In 2003, a total of 110 end- and interiortwo-flange loading tests of various floor joist assemblies were carried out at the University
of Waterloo (Fox, 2003) to determine the effect that an offset loading has on the strength of
typical floors. It was concluded that an additional limit should be placed on the bearing
stiffener offset to the load-bearing members above or beneath for cases where the bearing
stiffener is attached to the back of the joist as depicted in Figure B1.2.3-1.
As an alternative to in-line framing, the Standard permits the use of a structural load
distribution member that is specified in accordance with an approved design or approved
design standard. As an aid to designers, strength and stiffness have been determined
experimentally for various load-bearing top track assemblies (NAHB-RC, 2003; Dawe,
2005), including standard steel track, deep-leg steel track, and steel track with a 2x wood top
plate. Design guidance for some of the typical top track load distribution members is
available from the Cold-Formed Steel Engineers Institute (CFSEI, 2010a).
B1.2.5.2 Principles of Mechanics
The Standard does not aim to limit cold-formed steel light-framed shear walls, strap
braced walls and diaphragms to the configurations included in the Standard. As such, the
development of design values for other systems or configurations is permitted in
accordance with rational engineering procedures and principles of mechanics. Design
values based on calculations must, however, recognize the fundamental differences
between the expected performance of structures under wind and seismic loads, and the
performance of an individual lateral element. It must also be recognized that the
tabulated design values in the Standard are based on test data for individual lateral
elements. Recognition of these differences requires, where appropriate, that calculated
values be scaled per existing design data. For wind design, there is no modification in
design loads per the lateral resisting system used.
B1.3 Built-Up Sections
In 2007, a prescriptive end connection requirement for built-up compression members was
added in Section D1.2 (2) of AISI S100 (AISI, 2007a) to preclude any shear slip in a built-up
cold-formed steel section. This requirement was adopted from the AISC E6.2 (AISC, 2005a)
and CAN/CSA S16.1 (CSA, 1994) structural steel specifications.
In order to determine the applicability of this prescriptive end connection requirement for
double back-to-back cold-formed steel studs, a series of tests were conducted at the University
of Missouri-Rolla (UMR). This research by Stone and LaBoube (2005) demonstrated that
when a built-up stud is seated in a track section and bears on a firm surface, end slip is
precluded; and thus the need for the additional fasteners is not required. The UMR research
consisted of 32 tests of two C-shaped sections with edge stiffened flanges. The built-up
sections tested were 82.6 inches (2.1 m) long, between 3-5/8 inches (92 mm) and 6 inches (152
mm) in depth, and between 33 mils (0.84 mm) and 54 mils (1.37 mm) thick. The studs were
attached back-to-back with two rows of screws through the web starting 2 inches (50 mm)
from each end and spaced at 12 inches (305 mm), 24 inches (610 mm) or 36 inches (914 mm)
on-center. Each end of the built-up stud section was screwed to a standard track section 12
inches long which in turn was bearing on a 6x 8x (152mmm x 203 mm x 12.7 mm) steel
bearing plate. In order to simulate a pin connection representing an effective length factor of
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Commentary on the North American Standard For Cold-Formed Steel Structural Framing, 2015 Edition

unity, the steel bearing plate at each end was supported on a round bar.
In order to justify not specifying the end connection requirement of Section D1.2(b) of AISI
S100, the designer must meet the bearing condition of support on steel or concrete to ensure
relative slip of the two sections is prevented. This requires that the track must be supported
over the entire area of the built-up member by steel or concrete components and that bearing
stresses on the steel or concrete are within allowable limits.
B1.5 Connection Design
Self-drilling screws are the primary fastener type used in cold-formed steel construction,
although the Standard does not preclude the use of other fastener types.
B1.5.1 Screw Connections
B1.5.1.1 Steel-to-Steel Screws
Screws are the primary fastener type used in cold-formed steel framed construction,
although the Standard does not preclude the use of other fastener types. ASTM C1513
(ASTM, 2013) covers screws for the connection of cold-formed steel members manufactured
in accordance with ASTM Specifications C645 and C955. This specification also covers
test methods for determining performance requirements and physical properties.
However, the tensile or shear strength must be determined by test in accordance with
AISI S904 (AISI, 2013). General guidance on the selection of screws is given by the ColdFormed Steel Engineers Institute document Screw Fastener Selection for Cold-Formed Steel
Frame Construction (CFSEI, 2011).
Proper selection and installation of screws is necessary to ensure the design
performance. Screws are specified using a nominal size designator, not by diameter.
Table C-B1.5.1.1-1 defines suggested nominal screw diameters. The installation
requirements stated in this Standard are based on industry practice. Selection of a
minimum screw size is based on the total sheet thickness of the connection. Where
recommendations are not available, Table C-B1.5.1.1-2 provides suggested screw size for
steel-to-steel connections as a function of point style, per ASTM C1513, and total
combined thickness of all connected steel members.
Table C-B1.5.1.1-1
Suggested Screw Body Diameter
Nominal Screw Diameter, d
Screw Nominal Size
(inches)
(mm)
No. 6

0.138

3.51

No. 8

0.164

4.17

No. 10

0.190

4.83

No. 12

0.216

5.49

1/4

0.250

6.35

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AISI S240-15-C

Table C-B1.5.1.1-2
Suggested Screw Sizes For Steel-to-Steel Connections
Total Thickness of Steel 1
Screw
Point
Size
Style
(inches)
(mm)

0.024 0.095

0.61 2.41

No. 6

0.036 0.100

0.91 2.54

No. 8

0.036 0.100

0.91 2.54

No. 10

0.036 0.110

0.91 2.79

No. 12

0.050 0.140

1.27 3.56

No. 14

0.060 0.120

1.52 3.05

No. 18

0.060 0.120

1.52 3.05

No. 8

0.100 0.140

2.54 3.56

No. 10

0.110 0.175

2.79 4.45

No. 12

0.090 0.210

2.29 5.33

No. 14

0.110 0.250

2.79 6.35

No. 12

0.175 0.250

4.45 6.35

0.175 0.250

4.45 6.35

No. 12

4.5

0.145 0.312

3.68 7.92

No. 12

0.250 0.500

6.35 12.7

0.250 0.500

6.35 12.7

1 Combined

thickness of all connected steel members

B1.5.1.3 Spacing and Edge Distance

AISI S100 [CSA S136] (AISI, 2012a; CSA, 2012) stipulates that the center-to-center
spacing of screws be at least 3 times the screw diameter. During installation, if this
spacing is only 2 times the diameter, research at the University of Missouri-Rolla (Sokol
et al., 1999) has shown that the structural performance of the connection is reduced.
Guidelines for center-to-center spacing of less than 2 times the diameter are not
stipulated because the screw head diameter precludes a smaller spacing. The University
of Missouri-Rolla research serves as the basis for the requirements in the Standard.
B1.5.1.4 Gypsum Board
The Standard employs the use of the applicable building code as the guide for
provisions that cover the installation and attachment of gypsum panels to cold-formed
steel framing. The model building codes in the United States reference ASTM C1007
(ASTM, 2011d) as the appropriate standard for the gypsum board attachment to coldformed steel structural members.
The Standard requires that screw fasteners for gypsum board to steel connections be
in compliance with ASTM C954 (ASTM, 2011a), ASTM C1002 (ASTM, 2014a) or ASTM
C1513 (ASTM, 2013), as applicable, with a bugle head style. ASTM C954 is for fastening
to steel having a thickness from 0.033 inches (0.84 mm) to 0.112 inches (2.84 mm). ASTM
C1002 is for fastening to steel with a thickness less than 0.033 inches (0.84 mm). ASTM
C1513 is for fastening to steel with a thickness not greater than 0.118 inches (2.997 mm).

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Commentary on the North American Standard For Cold-Formed Steel Structural Framing, 2015 Edition

B1.5.2 Welded Connections

Additional guidance on welding of cold-formed steel members is provided in the ColdFormed Steel Engineers Institute document Welding Cold-Formed Steel (CFSEI, 2010b).
B1.5.3 Bolts
The Standard permits the use of bolts. Bolted connections can be designed by AISI S100
[CSA S136] equations.
B1.5.4 Power-Actuated Fasteners
The Standard permits the use of power-actuated fasteners. Connections using poweractuated fasteners can be designed by AISI S100 [CSA S136] equations.
B1.5.5 Other Connectors
The Standard permits the use of proprietary fasteners such as pneumatically driven
pins, rivets, adhesives, and clinches. Proprietary fasteners must be designed and installed
in accordance with the manufacturers requirements. The safety factor to be used in design
is to be determined by Chapter F of AISI S100 [CSA S136]. The Cold-Formed Steel
Engineers Institute has published technical notes pertaining to power-actuated fasteners
and pneumatically driven pins (CFSEI, 2012; CFSEI, 2009).
B2 Floor and Ceiling Framing
B2.5 Bearing Stiffeners
The Standard provides provisions for clip angle bearing stiffeners, based on research at
the University of Waterloo (Fox, 2006).
B2.6 Bracing Design
The continuous bracing and flange bracing provisions of the Standard were deemed
appropriate due to the availability of research and field experience with such assemblies. The
requirements in Section B2.6 were adapted from AISI S100 [CSA S136] requirements for
members where neither flange is attached to sheathing.
B3 Wall Framing
B3.2 Wall Stud Design
B3.2.1 Axial Load
Prior to 2004, the North American Specification for the Design of Cold-Formed Steel
Structural Members contained requirements for sheathing braced design in its Section D4(b).
In 2004, these provisions were removed. AISI S100 [CSA S136], (AISI, 2012a; CSA, 2012)
now permits sheathing braced design in accordance with an appropriate theory, tests, or
rational engineering analysis.
Sheathing braced design in the Standard is based on rational analysis assuming that the
sheathing braces the stud at the location of each sheathing-to-stud fastener location. Axial
load in the stud is limited, therefore, by the capacity of the sheathing or sheathing-to-wall
stud connection. Using the bracing principles as defined by Winter (1960) and summarized

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AISI S240-15-C

by Salmon and Johnson (1996), the equilibrium of an imperfect column braced at midheight, as illustrated in Figure C-B3.2.1-1, is expressed as:
L
P(+0)=k
(C-B3.2.1-1)
2 2
where
= Sidesway deflection at brace location beyond initial imperfection, 0
0 = Initial imperfection
L = Total stud height
k = Bracing stiffness
Following Eq. C-B3.2.1-1 to solve for deflection, :
P 0
=
kL
P
4
When P approaches kL/4, the lateral deflection approaches infinity. Therefore,
Pcr=kL/4. The bracing stiffness corresponding to Pcr is called kideal, and kideal = 4Pcr/L. To
provide sufficient bracing to a column subjected to load P, k needs to be greater than kideal.
It is common to choose k = 2kideal = 2(4P/L), and the corresponding deflection is:
=

P 0
P 0
=
= 0
kL
4P L
P 2
P
4
L 4

For 0 = L/960, the bracing force is

Fbr = k = 2

4P
0 = 0.8%P
L

Figure C-B.2.1-1 Column Lateral Bracing

This result is consistent with the requirement of 1%P from AISI S100 Equation
D3.3-1. In this Standard, a more conservative approach has been taken by considering a
safety factor of 2, which results in Fbr = 2%P. Since the tests indicated a failure of the
sheathing, not the screw-to-stud attachment, the Standard does not directly stipulate a
design requirement to check the screw-to-stud capacity or the screw capacity in shear.
The strength of gypsum sheathing attached with No. 8 and No. 6 screws is based on

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Commentary on the North American Standard For Cold-Formed Steel Structural Framing, 2015 Edition

tests by Miller (1989) and Lee (1995), respectively. Based on engineering judgment, a factor
of safety of 2.0 was applied to the ultimate load per screw (Table C-B3.2-1) when
determining the brace strength per screw for the gypsum wallboard. The ultimate loads
are based on the averaging of test data provided in Miller (1989) and Lee (1995).
Table C-B3.2-1
Brace Strength [Resistance] Per Screw
Limited by Gypsum Sheathing-to-Wall Stud Connection Capacity
Sheathing

Screw Size

Ultimate Load
(per screw)

Brace Strength
[Resistance](per screw)

1/2 inch (12.7 mm)

No. 6

0.117 kips (0.516 kN)

0.058 kips (0.258 kN)

1/2 inch (12.7 mm

No. 8

0.134 kips (0.596 kN)

0.067 kips (0.298 kN)

5/8 inch (15.9 mm)

No. 6

0.136 kips (0.605 kN)

0.068 kips (0.302 kN)

5/8 inch (15.9 mm)

No. 8

0.156 kips (0.694 kN)

0.078 kips (0.347 kN)

The maximum axial nominal load provided in Table B3.2-1 of the Standard was
determined by first multiplying the brace strength [resistance] per screw given in
Commentary Table C-B3.2-1 by 2 to recognize that sheathing must be attached to both stud
flanges and then dividing by 0.02 (i.e., 2%P), thus solving for the nominal load P that is
given in Table B3.2-1 of the Standard.
The unbraced length with respect to the minor axis and the unbraced length for torsion
are taken as twice the distance between the sheathing connectors in the event that an
occasional attachment is defective to a degree that it is completely inoperative.
If plywood sheathing is attached to both flanges of the wall stud by screws spaced no
greater than 12 inches (305 mm) on center, both the plywood and the stud must be checked.
The following outlines a possible design solution for plywood attached to a wall stud:
Evaluation of the Plywood:
Using NDS (AFPA, 1997) Section 11.3,
Nominal Design Value (Brace Strength), Z = D m Fem/Rd
D = 0.164 (4.17 mm) (No. 8 Screw)
m

= Sheathing thickness = 0.5 (12.7 mm)

= 2.2 for D 0.17 (4.32 mm)

Fem = 1900 psi (13,100 kPa) (lowest bearing strength value the values are based on
the specific gravity of the wood)
Z = 0.164 x 0.5 x 1900 / 2.2 = 70.82 lbs. (315 N)
Brace Force, Fbr = 0.02 P, where P is the axial load in the stud.
P

= 70.82/0.02 = 3,540 lbs (15,700 N) = 3.5 kips (15.6 kN) per screw x 2 screws = 7.0
kips
(31.1 kN) per stud
Evaluation of the Steel Wall Stud:
The screw capacity in the stud can be evaluated using Section E4.3 of AISIS100 [CSA
S136],
where
Pns = 4.2 (t3d)0.5 Fu 2.7 tdFu
= 3.0
If Pns/ < Z, the brace force analysis to determine P should be based on the lower
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AISI S240-15-C

value. The capacity per screw is computed by the following equation:

P = (Pns/ < Z)/0.02
Because the Standard requires that sheathing must be attached to both flanges of the
wall stud, the nominal axial load in the wall stud is twice the value of P.
B3.2.5 Web Crippling
B3.2.5.1 Stud-to-Track Connection for C-Section Studs
When the track thickness is equal to or greater than the stud thickness, an increase in
web crippling strength can be realized. This increased strength is attributed to the
favorable synergistic effect of the stud-to-track assembly. The provisions are based on
research conducted at the University of Waterloo (Fox and Schuster, 2000) and the
University of Missouri-Rolla (Bolte, 2003).
Two proposed design equations were considered for adoption by Section B3.2.5.1 of
the Standard for evaluating the design strength of the stud-to-track connection for curtain
wall applications. The proposed UMR equation (Bolte, 2003) reflected the specific
contribution of the screw as follows:
Pnst = Pn + Pnot
(C-B3.2.5.1-1)
where

= 0.756
Pn = Web crippling capacity in accordance with Section C3.4.1 of AISI S100 [CSA
S136] for end one-flange loading
Pnst = Nominal strength [resistance] for the stud-to-track connection when subjected to
transverse loads
Pnot = Screw pull-out capacity in accordance with Section E4.4.1 of AISI S100 [CSA
S136]
The proposed equation (C-B3.2.5.1-2) was based on a formulation proposed by Fox
and Schuster (2000). The design formulation for the stud-to-track connection was based on
a pure web crippling behavior consistent with Section C3.4 of AISI S100 [CSA S136]. To
reflect the positive contribution of the screw attachment, Fox and Schuster (2000)
proposed modified web crippling coefficients as follows:

R
N
h

1 + C N
1 C h
(C-B3.2.5.1-2)
Pn = Ct 2 Fy sin 1 C R

t
t
t

where
Pn = Nominal web crippling strength [resistance] per Section C3.4.1 of AISI S100
[CSA S136] with the following coefficients:
C = Web crippling coefficient = 5.6
CR = Inside bend radius coefficient = 0.01
CN = Bearing length coefficient = 0.30
Ch = Web slenderness coefficient = 0.14
R
= Stud inside bend radius
N = Stud bearing length
h
= Depth of flat portion of stud web measured along plane of web
t
= Stud design thickness

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Commentary on the North American Standard For Cold-Formed Steel Structural Framing, 2015 Edition

= Angle between plane of web and plane of bearing surface, 45<90

Based on the additional tests performed at UMR and the University of Waterloo, the
following coefficients are recommended:
C = Web crippling coefficient = 3.7
CR = Web slenderness coefficient = 0.19
CN = Bearing length coefficient = 0.74
Ch = Inside bend radius coefficient = 0.019
Although there are pros and cons to each design equation, statistically they yield
similar results as shown in the following:
Table B3.2.5.1-1
Comparison of Proposed Design Equations
Parameter

Waterloo Model

UMR Model

Mean

1.001

1.000

Coeff. of Variation

0.101

0.078

(LRFD)

1.74

1.71

0.88

0.90

The safety factor and resistance factor are based on assuming a member failure mode,
not a connection failure mode.
Although both the UMR and University of Waterloo design methods will yield
similar design strengths, for simplicity of design it was decided to adopt the University
of Waterloo design method for the Standard. For simplicity, since = 90 and therefore
sin = 1, the sin term was eliminated from Equation B3.2.5.1-1.
When the track thickness is less than the stud thickness, the proposed provisions are
based on the study by Fox and Schuster (2000).
The 0.5 applied to Pnst for locations adjacent to wall openings is based on a study by
Daudet (2001).
Further research on these stud-to-track connections was carried out in 2008 at the
University of Waterloo (Lewis, 2008), with the objective being to extend the design
provisions in Section B3.2.5.1 of the Standard to cover jamb stud members. These jamb
studs can be single C-shaped members or built-up sections made from multiple members.
The scope of testing was limited to the following:
1. Single C-shaped stud members located at the end of the track with two orientations of
the stud: with the stiffening lips adjacent to the track end, and with the stud web
adjacent to the track end.
2. Two C-shaped studs connected back-to-back, positioned in the track away from the
track end, and positioned at the end of the track.
3. Two C-shaped studs connected toe-to-toe, positioned in the track away from the track
end, and positioned at the end of the track.
The research showed that the web crippling expression in the Standard can be
applied to all other combinations of single C-shaped and built-up members simply by
changing the global web crippling coefficient, C. It was determined that the strength of
other jamb stud configurations were multiples of the C=3.7 for a single stud. For
example, a single member at the end of a track is 0.5C = 1.85; toe-to-toe or back-to-back
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AISI S240-15-C

members are 2C = 7.40; toe-to-toe members at the track end are 1.5C = 5.55; and single
stud at the track end with the stiffening lips adjacent to the opening are 0.75C = 2.78.
These results can only be applied within the range of the test parameters. For the web
crippling failure mode to occur, the screws connecting the stud-to-track need to be sized
according to the stud thickness. Provisions have been added for minimum screw sizes
for the various stud thicknesses.
These tests were limited to combinations of stud and track where the track was the
same thickness as the stud. This avoided the possibility of a track punch-through failure
for the single C-shaped studs and for the toe-to-toe built-up members, but not for the
back-to-back members. Consequently, a new design limit state for the track punchthrough failure mode is proposed for the back-to-back built-up jamb members.
In situations where the back-to-back jamb stud configurations do not have screws
connecting both flanges to the track, the web crippling strength [resistance] of the studs
must be calculated using the provisions of AISI S100 [CSA-S136]. Since the AISI S100 web
crippling calculations for back-to-back built-up sections overestimate the nominal
strength [resistance] of these jamb studs, the nominal strength [resistance] is calculated using
twice the AISI S100 web crippling capacity for a single web member.
The safety factors and resistance factors were determined based on the test data. As a
result, there are different factors for different jamb stud configurations.
B3.2.5.2 Deflection Track Connection for C-Section Studs
The provisions contained in the Standard apply to a C-section wall stud installed in a
single deflection track application and are based on research at the Milwaukee School of
Engineering (Gerloff, 2004). Based on this research, the load capacity [resistance] can be
established by the equations in the Standard. The key parameters, as given by the
equations, are illustrated by Figure C-B3.2.5.2-1.
wdt

Track

Stud

bstud
Figure C-B3.2.5.2-1 Deflection Track Connection

Because the deflection track detail does not provide torsional restraint for the wall
stud, it is recommended that a line of bridging be installed near the end of the member.
For Figure C-B3.2.5.2-1, dimension e is selected for the sum of construction
tolerances and the deflection of the floor above relative to the floor or foundation below.
Dimension D is selected so that adequate stud to track engagement and web crippling
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Commentary on the North American Standard For Cold-Formed Steel Structural Framing, 2015 Edition

bearing length remain when the floor below deflects relative to the floor above.
The background research for this provision did not include studs at or near
terminations in the top track. For this case, the strength and serviceability of the
connection may be reduced.
B3.3 Header Design
Box and back-to-back header beams have been commonly used in cold-formed steel framing.
The geometry is fabricated using two C-shaped cold-formed steel members. Design practice for
such header beams can be based on AISI S100 [CSA S136], (AISI, 2012a; CSA, 2012). Research
has determined that the application of AISI S100 [CSA S136] design provisions is
conservative when track members are included in the assembly. This led to the development
of an improved design methodology.
L-header beam geometries are gaining popularity in cold-formed steel framing. The
geometry is fabricated using one or two L-shaped cold-formed steel members connected to a
top track section. This geometry is commonly referred to as a single or double L-header
because one or two angle shapes are used to create the header.
The header design provisions in the Standard do not attempt to provide a complete
methodology for the design of openings in buildings. For such, the designer must consider
numerous loading and serviceability issues (including out-of-plane loads) and design a
complete load path consisting of members and connections that may include cripple studs, jack
studs, king studs, head tracks and sill tracks. A useful reference for designers on this subject is
the AISI Cold-Formed Steel Framing Design Guide (AISI, 2007).
B3.3.1 Back-to-Back Headers
The design methodology is based on review and analysis of the data presented in the
NAHB (2003a) report Cold-Formed Steel Back-To-Back Header Assembly Tests (1997) and the
study of Stephens (2000, 2001). The test results were evaluated and compared with the
strength equations contained in the 2001 edition of the AISI Specification.
Stephens and LaBoube (2000) concluded that web crippling or a combination of
bending and web crippling is the primary factor in header beam design for the IOF (interior
one-flange) loading condition. Neither pure shear nor combined bending and shear were
failure modes in the test program. The research study showed that using AISI S100 [CSA
S136] web crippling equations for shapes having single webs for the design of box or backto-back header beams gave conservative results.
B3.3.2 Box Headers
Based on studies conducted by Stephens (2001), a modification factor was derived that
enables the computation of the interior one-flange web crippling capacity of a box header
assembly as defined by Figure C3.4.4-2 of the Standard. The increased web crippling
capacity is attributed to the interaction of the track section and the C-shaped section; thus, it
is imperative that the track section be attached with the flanges as shown in Figure C3.4.4-2.
This interaction is quantified by the ratio of track thickness to C-shaped section thickness in
Eq. B3.3.2.3-1. When computing the web crippling capacity for a header assembly, the
nominal capacity computed using AISI S100 [CSA S136] is to be multiplied by 2 to reflect
that there are two webs in the assembly. In addition to a modification to the pure web
crippling strength, the Standard also contains an interaction equation for bending and web
crippling of box header assemblies that differs from AISI S100 [CSA S136]. This interaction

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AISI S240-15-C

equation is based on the research of Stephens (2001), which included test specimens having
standard perforations. Thus, the provisions of AISI S100 [CSA S136] are appropriate for
header design.
If the top track section of a box header assembly is attached with the flanges up, as would
be the case where the header beam is located directly above the opening and beneath the
cripple studs, the provisions of Section B3.3.2.3 would not apply. Web crippling capacity and
the combination of bending and web crippling should be evaluated by using Sections C3.4
and C3.5 of AISI S100 [CSA S136], and the equations for shapes having single unreinforced
webs should be used.
The procedure to calculate the vertical deflection of a box or back-to-back header may be
accomplished by using a composite assembly calculation, which would include the two Cshaped sections and the top and bottom tracks. However, to achieve full composite action,
using this type of calculation would require an extensive (cost-prohibitive) fastener
requirement between the tracks and the C-shaped sections; and therefore, it is more common
to use a conservative estimate of the vertical deflection based on the full moment of inertia
of the two C-shaped sections alone.
See Section B3.3.1, Back-to-Back Header, for additional information, as applicable.
B3.3.3 Double L-Headers
The available test data (Elhajj and LaBoube, 2000; and LaBoube, 2004) indicated that the
failure mode was flexure or combination of flexure and web crippling. Neither pure shear
nor combined bending and shear were failure modes in the test program. The tested
moment capacity, Mt, was determined and compared with the computed moment capacity
as defined by Section C3.1.1(a) of AISI S100 [CSA S136]. The nominal flexural strength
[resistance] was computed using the following equation:
(C-B3.3.3-1)
Mn = Sxc Fy
where
Fy = Measured yield stress
Sxc = Elastic section modulus of the effective section computed at f = Fy.
The section modulus of the compression flange was used for all computations.
It should be noted that the flexural strength is based on the section modulus of the
compression flange; i.e., yielding of the shorter, horizontal leg of the angle. The inelastic
reserve capacity of the longer, vertical leg is recognized and yielding in the extreme tensile
fiber is not considered a limit state.
It should also be noted that when the design provisions of the Standard were
developed, the elastic section modulus of the effective section was computed assuming
that when the free edge of the element was in tension, Equations B2.3-3, B2.3-4 and B2.3-5
of AISI S100 [CSA S136] would apply regardless of the magnitude of ho/bo. Therefore,
these assumptions are appropriate when calculating the elastic section modulus of the
effective section using the Standard.
For typical L-headers having a geometry as defined by the limitations of Section B3.3.3,
the performance of full-scale double L-header beam tests (Elhajj and LaBoube, 2000; and
LaBoube, 2004) has shown that the limit states of shear, web crippling, bending and shear,
and bending and web crippling need not be considered when designing an L-header beam.
This is because shear and web crippling failures were not indicated in any of the tests, and
because a simplified conservative design approach is used. Web crippling is effectively
prevented by the way L-headers are assembled. However, designers are cautioned that an
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Commentary on the North American Standard For Cold-Formed Steel Structural Framing, 2015 Edition

L-header could potentially fail in shear for the combination of a very short span and a very
large loading. Currently there are no limitations prescribed on minimum lengths or other
factors that would prohibit shear failure in such cases. However, as a suggested procedure,
shear should probably be considered when the span-to-depth ratio is less than 3.
The procedure to calculate the vertical deflection of an L-header is undefined because
the L-header is an indeterminate assembly consisting of two angles, cripple studs, and track
sections interconnected by self-drilling screws. However, the test results indicate that the
measured assembly deflections at an applied load that equaled the nominal load [specified
load] was less than L/240. Further analytical work, based on test data, would be necessary
in order to develop a calculation procedure to determine the deflection of L-header beams.
B3.3.3.1.1 Gravity Loading
The test results summarized by Elhajj and LaBoube (2000) and LaBoube (2004) are
considered to be confirmatory tests that show AISI S100 [CSA S136] Section C3.1.1
provides an acceptable determination of the nominal flexural strength [resistance].
For the 10-inch (254-mm)-deep L-header beams having the span to vertical leg
dimension, L/Lh, greater than 10, the tested header sections had tested moment
capacities greater than the computed moment capacity defined by Eq. B3.3.3.1.1-1 in
the Standard. However, for 10-inch (254-mm)-deep beams having L/Lh ratios less
than 10, the tested moment capacity was on the average 10% less than the computed
moment capacity (Elhajj and LaBoube, 2000). Thus, the application of Eq. B3.3.3.1.1-1
is questionable for full range of the 10-inch (254-mm) L-headers. A review of the data
indicates that the application of Eq. B3.3.3.1.1-1 is valid for test specimens having a
span to vertical leg dimension, L/Lh, of 10 or greater. For the specimens having L/Lh
ratios less than 10, it is proposed that the results obtained by using Eq. B3.3.3.1.1-1 be
multiplied by 0.9.
B3.3.3.1.2 Uplift Loading
A comparison of the tested to computed moment capacity ratios ranged from
0.141 to 0.309 with a mean of 0.215 (Elhajj and LaBoube, 2000). Further analysis of the
tested to computed moment ratios indicated that the behavior was influenced by the
ratio of Lh/t. Therefore, uplift reduction factors, R, in the Standard were developed as
a function of the Lh/t ratio.
Based on the provisions of Chapter F of AISI S100 [CSA S136], the safety factor was
computed to be 2.0.
B3.3.4 Single L-Headers
Prior to 2003, the Standard excluded single L-headers. The NAHB Research Center
(2003a) study that was completed prior to 2003 tested both single and double L-header
beams. The tests consisted of either a single-point load or a two-point load. All angles had
a 1.5 inch (38.1 mm) top flange. The vertical leg dimensions were either 6, 8, or 10 inches
(152, 203 or 254 mm). Thicknesses ranged from nominally 0.033 to 0.068 inches (0.84 to 1.73
mm). Test span lengths ranged from 36 to 192 inches (914 to 4880 mm).
An analysis of the data indicated that the behavior of the L-headers differed for singleversus double-angle geometries. Also, the single-point load produced test results that
differed from the two-point load. Prior to 2003, there was insufficient data to develop
design guidelines for single-angle L-headers. Thus, the data analysis did not consider data
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AISI S240-15-C

for the single-angle sections nor for the single-point loading.

In 2003, testing was completed at the NAHB Research Center (2003a) on single L-header
beams. The tests were similar to the previously tested double L-header beam tests, but
header sizes were limited to vertical leg dimensions of 6 and 8 inches (152 or 203 mm),
thicknesses ranged from nominally 0.033 to 0.054 inches (0.84 to 1.37 mm), and spans were
limited to 4 feet (1.219 m). From this testing, sufficient data was provided to develop
design guidelines for single L-headers within the range of parameters tested.
LaBoube (2004), based on testing by the NAHB Research Center (2003a), demonstrated
that the design methodology for double L-headers in the 2001 edition of the AISI Standard
for Cold-Formed Steel FramingHeader Design was acceptable for evaluating the gravity
moment capacity of single L-headers, within the limitations of the test program. Uplift tests
on single L-headers were not performed as part of this test program; however, Section
B3.3.4.1.2 has been reserved in the Standard for this eventuality. Further, using the
provisions of Section F1 of AISI S100 [CSA S136], the same and factors that were
prescribed in the 2001 edition of the AISI Standard for Cold-Formed Steel FramingHeader
Design for the design of double L-headers would apply to single L-headers. As with
previously tested double L-headers, neither pure shear nor combined bending and shear
were failure modes for the tested single L-headers. Also, web crippling and combined
bending and web crippling would be precluded from occurring because of the requirement
that concentrated load applications occur at cripple stud locations.
B3.3.5 Inverted L-Header Assemblies
In 2005, provisions for inverted L-headers, as shown in Figure C-B3.3.5-1, were added to
the Standard, based on rational engineering judgment, as a means to provide improved
capacity for double and single L-headers.

For Canada 1 in. = 25.4 mm

Figure C-B3.3.5-1 Inverted Single or Double L-Header Assembly

(Inverted Single L-Header Shown)

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Commentary on the North American Standard For Cold-Formed Steel Structural Framing, 2015 Edition

B3.4 Bracing
The requirement in the Standard that each brace be designed for 2% of the design
compression load [force] in the member is based on a long-standing industry practice. See
further discussion in Commentary Section B3.2.1.
Bracing requires periodic anchorage. Bracing forces are accumulative between anchorage
points.
B3.4.1 Intermediate Brace Design
Brace forces are additive, thus the Standard requires consideration of combined brace
forces that when designing braces for members that experience combined loading. Design
guidance is provided in AISI D110 (AISI, 2007).
B3.5 Serviceability
The Standard does not stipulate serviceability limit states. However, the International
Building Code (ICC, 2015) sets forth deflection limits in Sections 1604.3 and 1405.10.3, and the
NFPA 5000 (NFPA, 2015) sets forth similar provisions in Section 35.1.2.8 for use in the United
States and Mexico. Likewise, the Users Guide - NBC 2010 Structural Commentaries (Part 4, of
Division B) (NRCC, 2010) sets forth deflection limits for use in Canada.
B4 Roofing Framing
B4.5 Bracing Design
The continuous bracing and flange bracing provisions of the Standard were deemed
appropriate due to the availability of research and field experience with such assemblies. The
requirements in Section B4.5(b) were adapted from AISI S100 [CSA S136] requirements for
members where neither flange is attached to sheathing.
B5 Lateral Force-Resisting Systems
The lateral design provisions of the Standard were initially based on the requirements in the
International Building Code (ICC, 2003) and the NFPA 5000 Building Construction and Safety Code
(NFPA, 2003). The provisions in those codes evolved since the early work of Tarpy (1976-80),
APA-The Engineered Wood Association (1993), Serrette (1995a) and the shear wall provisions
that were first introduced into the 1997 Uniform Building Code (ICBO, 1997). Research conducted
by Serrette at Santa Clara University and Dolan at Virginia Polytechnic Institute and State
University form the technical basis for the initial design values in the Standard. Specific
references to this research are cited in this Commentary. In 2007, provisions and design values
related to shear wall and strap braced wall design, which are to be used with the 2005 National
Building Code of Canada [NBCC] (NRCC, 2005), were added to the Standard based largely on
research carried out under the supervision of Rogers at McGill University between 2005 and
2007. Specific references to this research are cited in the Commentary on ASI S400. At this time,
the Standard does not address the Canadian design of diaphragms. Studies are ongoing, and it is
expected that the Canadian design of these elements will be addressed in future editions of the
Standard.
B5.2 Shear Wall Design
Shear walls are to be designed as either Type I shear walls or Type II shear walls.

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AISI S240-15-C

B5.2.1 General
Type I shear walls are fully sheathed with steel sheet sheeting, wood structural panels,
gypsum board panels, or fiberboard panels with hold-downs at each end. Type I shear walls
sheathed with steel sheet sheathing or wood structural panels are permitted to have openings
where details are provided to account for force transfer around openings. Figures C-B5.2.11(a) and C-B5.2.1-1(b) show typical Type I shear walls, with and without detailing for force
transfer around window openings, and with hold-down anchors at the ends of each wall
segment. Where wall assemblies are engineered for force transfer around openings and
engineering analysis shows that uplift restraint at openings is not required, the assembly
may be treated as a Type I shear wall and hold-downs are required at the ends of the
assembly only, as illustrated in Figure C-B5.2.1-1(b).
Type II shear walls are sheathed with steel sheet sheeting or wood structural panels with a
Type II shear wall segment at each end. Openings are permitted to occur beyond the ends of
the Type II shear wall; however, the width of such openings shall not be included in the
length of the Type II shear wall. Figure C-B5.2.1-2 shows a typical Type II shear wall.

Figure C-B5.2.1-1(a) Type I Shear Walls Without Detailing for Force Transfer Around Openings

Figure C-B5.2.1-1(b) Type I Shear Wall With Detailing for Force Transfer Around Openings

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Commentary on the North American Standard For Cold-Formed Steel Structural Framing, 2015 Edition

Figure C-B5.2.1-2 Typical Type II Shear Wall

B5.2.2 Nominal Strength [Resistance]

Since the tabulated values in the Standard are based on test data, it was deemed
necessary to provide the user with the limiting values of the tested systems. The intent is
not to prevent an engineer from using judgment, the principles of mechanics and
supplemental data to develop alternate shear values from those shown in the Standard, as
discussed in Section B1.2.5.2 above.
For both wood structural panels and steel sheet sheathing, aspect ratios up to 4:1 are
permitted with reductions in nominal strength. The reduced strength values are
conservative based on 4:1 aspect ratio tests conducted by Serrette (1997).
A shear wall assembly using an approved adhesive to attach shear wall sheathing to the
framing is not yet recognized by this Standard or by ASCE 7. Sufficient test data to justify
acceptance of shear walls that use adhesive alone or in combination with fasteners to attach
sheathing to the framing members was not available at the time this Standard was written.
The limited existing test data indicates that shear walls using adhesives for sheathing
attachment will generally not perform the same as shear walls with only fasteners attaching
the sheathing to the framing.
Overdriving of the sheathing screws will result in lower strength, stiffness and ductility
of a shear wall compared with the values obtained from testing (Rokas, 2006); hence,
sheathing screws should be firmly driven into framing members but not overdriven into
sheathing.
B5.2.2.1 Type I Shear Walls
In the United States and Mexico: The initial requirements for Type I shear walls in the
Standard were based on studies by Serrette (1996, 1997 and 2002). This series of
investigations included reverse cyclic and monotonic loading and led to the
development of the design values and details for plywood, oriented strand board (OSB),
and gypsum wall-board (GWB) shear wall assemblies that are included in the Standard.
In the United States and Mexico: In 2006, requirements were established for Type I
shear walls with fiberboard panel sheathing based on studies by the NAHB Research
Center (NAHB, 2005) and by the American Fiberboard Association (PFS, 1996 and
NAHB, 2006). The nominal strength values for shear walls faced with fiberboard in Table
B5.2.2.3-4 were based on monotonic tests of fiberboard sheathed, cold-formed steel framed
shear walls and were compared to the tests that are the basis of the building code
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AISI S240-15-C

tabulated capacities for fiberboard sheathed, wood-framed shear walls. For the 2-inch (50.8
mm) and 3-inch (76.2-mm) edge screw spacing, the nominal strength values in Table
B5.2.2.3-4 were based on the average peak load from tests of two 8-foot (2.438 m)-wide
by 8-foot (2.428 m)-tall wall specimens. These nominal strength values were found to be
within 90 percent of the nominal strength values for similarly sheathed wood-framed
walls. The ratio of steel-to-wood nominal strength values increased as the edge
(perimeter) fastener spacing increased and, therefore, extrapolating the 2/6 (92% ratio)
and 3/6 (96% ratio) design values to 4/6 using a ratio of 90% was conservative. For the
4-inch (101.6 mm) edge screw spacing, the nominal strength values were calculated as 90
percent of the nominal strength value for a similarly sheathed wood-framed wall.
In the United States and Mexico: In 2011, the maximum aspect ratio of shear wall
covered with 0.027 steel sheet sheathing on single side of the shear wall was established
based on the experiments performed at the University of North Texas (Yu, 2007). In
addition, the nominal strength values for 0.030 and 0.033 steel sheet sheathing on one side
were added. The addition was also based on testing at the University of North Texas
(Yu, 2007; Yu et al., 2009). Designation thicknesses of stud, track and blocking, and required
sheathing screw size were added to the tables as well.
In the United States and Mexico: The Effective Strip Method for determining the
nominal shear strength [resistance] for Type I shear walls with steel sheet sheathing is based
on research by Yanagi and Yu (2014). The method assumes a sheathing strip carries the
lateral load via a tension field action as illustrated in Figure C-B5.2.2.1-1. The shear
strength of the shear wall is controlled by the tensile strength of the effective sheathing
strip, which is determined as the lesser of the fasteners tensile strength and the yield
strength of the effective sheathing strip. The statistical analysis in Yanagi and Yu (2014)
yielded an LRFD resistance factor of 0.79 for the Effective Strip Method. In order to keep
consistency in resistance factors (0.65 for LRFD) specified in Standard Section B5.2.3, the
original design equation in Yanagi and Yu (2014) was adjusted accordingly.

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Commentary on the North American Standard For Cold-Formed Steel Structural Framing, 2015 Edition

Figure C-B5.2.2.1-1 Effective Strip Method Model for Steel Sheet Sheathing

In the United States and Mexico: The nominal strengths [resistances] were based on
tests with studs with 1.5-inch (38 mm) x 4-inch (100 mm) punchouts at a center-to-center
spacing of 24 inches (600 mm), anchor bolts with standard cut washers, and hold-down
anchors on each end of the wall. As a result, the Standard permits the use of studs with
standard punchouts and anchor bolts with standard cut washers, and requires hold-down
anchors even though calculations may demonstrate that hold-down anchors are not
necessary.
In the United States and Mexico: Factors were included, based on load duration
factors given in the 2005 NDS (AFPA, 2005a) as shown in Table C-B5.2.2-1, to account for
the influence of the duration of the applied load on wood strength to allow the tabulated
values to be used for other in-plane lateral loads. Since the shear wall tests used as the
basis of the Standard were carried out over a short time span, the tabulated values are
for short-term duration loads (i.e., wind or seismic). However, the tabulated values for
diaphragms were calculated using a load duration factor of 1.33, rather than the factor of
1.6 given in the 2005 NDS.
Table C-B5.2.2-1
United States and Mexico
AFPA NDS Load Duration Factors

Load Duration
Permanent
Ten years
Two months
Seven days
Ten minutes

Factor
0.9
1.0
1.15
1.25
1.6

Typical Design Loads

Dead Load
Occupancy Live Load
Snow Load
Construction Load
Wind/Earthquake Load

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AISI S240-15-C

In Canada: Nominal resistance values for steel sheet sheathed and wood structural panel
sheathed shear walls in AISI S240 match the values in AISI S400. Refer to the
Commentary on AISI S400 for information on the derivation of these values. Nominal
resistance values for gypsum and fiberboard sheathed shear walls in AISI S240 were set at
80% of the values found in Tables B5.2.2.3-3 and B5.2.2.3-4 for the United States. This
reduction in resistance level is similar to what is found for the wood sheathed walls of
similar construction, i.e. Table B5.2.2.3-2.
B5.2.2.2 Type II Shear Walls
The requirements for Type II shear walls, also known as perforated shear walls, in
Section B5 were based on provisions in NEHRP (2000) for wood systems. In this method,
the shear capacity ratio, F, or the ratio of the strength of a shear wall segment with
openings to the strength of a fully sheathed wall segment without openings, is
determined as follows:
r
(C-B5.2.2.2-1)
F=
3 2r
where
1
(C-B5.2.2.2-2)
r=
A0
1+
h Li
A0 = Total area of openings
h = Height of wall
L i = Sum of the length of full-height sheathing
Research by Dolan (1999, 2000a, 2000b) demonstrated that this design procedure is
as valid for steel-framed systems as for all wood systems, and the IBC (ICC, 2003) and
NFPA 5000 (NFPA, 2003) building codes both permit the use of Type II shear walls for
steel systems. Test results revealed the conservative nature of predictions of capacity at
all levels of monotonic and cyclic loading. The Standard does not provide a method or
adjustment factor for estimating the lateral displacement of Type II shear walls. As such,
the user should be cautious if a Type II shear wall is used in a deflection-sensitive design.
Table B5.2.2.2-1 in the Standard, which establishes an adjustment factor for the shear
resistance, is based on the methodology described in this section and exists in essentially
the same form in both the wood and steel chapters of the IBC (ICC, 2003) building code.
There is also a similar table in AISI S230 (AISI, 2012h); however, AISI S230 establishes an
adjustment factor for the shear wall length rather than the shear wall resistance.
Although the Dolan work was based on wood structural panel sheathing, the
Committee felt it was appropriate to extend this methodology to shear walls with steel
sheet sheathing due to the similar performance of wood structural panel sheathing and steel
sheet sheathing in monotonic and cyclic tests (Serrette, 1997) of Type I shear walls.
In accordance with Section B5.2.2.2 in the Standard, it is required to check the
height/length ratio of each Type II shear wall segment and reduce the strength of each
segment that has an aspect ratio greater than 2:1, but less than or equal to 4:1 by the
factor of 2w/h. This aspect ratio reduction factor is cumulative with the shear resistance
adjustment factor, Ca.

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Commentary on the North American Standard For Cold-Formed Steel Structural Framing, 2015 Edition

B5.2.3 Available Strength [Factored Resistance]

In the United States and Mexico: With the adoption of AISI S400, North American
Standard for Seismic Design of Cold-Formed Steel Structural Systems, the seismic requirements,
including the resistance factors, , and safety factors, , were eliminated from AISI S240.
Seismic design using the provisions of AISI S240 are only permitted in Seismic Design
Category A, or in Seismic Design Categories B or C if the Response Modification Factor, R,
in accordance with ANSI/ASCE 7-10 Table 12.2-1, is equal to 3. For these conditions,
where special seismic detailing is not required, the lower resistance factor, , and higher
safety factor, , typically required for seismic design, are not warranted.
In Canada: The resistance factor () in AISI S240 matches the value in AISI S400. Refer to
the Commentary on AISI S400 for information on the derivation of this value.
B5.2.5 Design Deflection
The deflection provisions are based on work performed by Serrette and Chau (2003).
Equation C-B5.2.5-1 may be used to estimate the drift deflection of cold-formed steel lightframed shear walls recognized in the building codes. The equation should not be used
beyond the nominal strength values given in the Standard. The method is based on a simple
model for the behavior of shear walls and incorporates empirical factors to account for
inelastic behavior and effective shear in the sheathing material. Specifically, the model
assumes that the lateral deflection (drift) of a wall results from four basic contributions:
linear elastic cantilever bending (boundary member contribution), linear elastic sheathing
shear, a contribution for overall nonlinear effects, and a lateral contribution from
anchorage/hold-down deformation. These four contributions are additive.

Figure C-B5.2.5-1 Lateral Contribution From Anchorage/Hold-Down Deformation

v
2 vh 3
vh
h
=
+ 1 2
+ 1 5 / 4 2 3 4 + v
Gt sheathing
3E s A c b
b
b

Linear elastic cantilever bending:

2 vh 3
3E sA c b

Linear elastic sheathing shear: 1 2

Gt sheathing

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(C-B5.2.5-1)
(C-B5.2.5-2)
(C-B5.2.5-3)

AISI S240-15-C

v
Overall nonlinear effects: 15 / 4 2 3 4

(C-B5.2.5-4)

h
(C-B5.2.5-5)
v
b
The lateral contribution from anchorage/hold-down deformation is dependent on the
aspect ratio of the wall, as illustrated in Figure C-B5.2.5-1. The empirical factors used in the
equation are based on regression and interpolation analyses of the reversed cyclic test data
used in development of the cold-formed steel shear wall design values. The term in the
linear elastic sheathing shear expression attempts to account for observed differences in the
response of walls with similar framing, fasteners and fastener schedules, but different
sheathing material. Low values of for steel sheet sheathing are a result of shear buckling in
the sheet. The equations were based on Type I shear walls without openings, and the user
should use caution if applying them to Type I shear walls with openings or to Type II shear
walls. The shear wall deflection equations do not account for additional deflections that may
result for other components in a structure (for example, wood sills and raised floors).
For wood structural panels, the shear modulus, G, is not a readily available value,
except for Structural I plywood panels in the IBC (ICC, 2003) and UBC (ICBO, 1997) codes.
However, the shear modulus may be approximated from the through thickness shear
rigidity (Gvtv), the nominal panel thickness (t) and through thickness panel grade and
construction adjustment factor (CG) provided in the AFPA Manual (AFPA, 2001). For
example, G for 7/16-in. 24/16 OSB rated sheathing can be approximated as follows:
Gvtv (24/16 span rating) = 25,000 lb/inch (strength axis parallel to framing)
t = 0.437 inch (as an approximation for tv)
CG = 3.1
G (approximate) = 3.1 x 25,000 / 0.437 = 177,300 psi
Thus, CGGvtv = 77,500 lb/inch and Gt = 77,500 lb/inch
A comparison of the CGGvtv and Gt values suggests that using the nominal panel
thickness as an approximation to tv is reasonable given that the deflection equation
provides an estimate of drift.
Currently, the shear wall deflection equations do not include provisions for gypsum
board or fiberboard shear walls. However, the reader is reminded that given the low seismic
response modification coefficient, R, assigned by the building codes to gypsum board shear
walls, it is expected that these systems will perform in the elastic range of behavior and
deflections will be less likely to control the design.
In 2012, coefficients b and in deflection Equation B5.2.5-1 were revised for Canadian
Soft Plywood (CSP), and steel sheet sheathing, based on research results compiled by Cobeen
(2010). CSP was differentiated from other plywoods based on the performance of that
material. It should be noted that Canadian Douglas Fir Plywood (DFP) was found to
behave similarly to plywood in common use in the United States.

Lateral contribution from anchorage/hold-down deformation:

B5.3 Strap Braced Wall Design

For strap braced walls, it is acceptable to compute the deflection using standard
engineering analysis. Deflection calculations should consider all elements that contribute to
the horizontal top of wall displacement, including axial deformation of the studs, elongation
of the straps, and a lateral contribution from anchorage/hold-down deformation, as well as
additional deflections that may result for other components in a structure (for example, wood
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Commentary on the North American Standard For Cold-Formed Steel Structural Framing, 2015 Edition

sills and raised floors). Because loose straps permit lateral displacement without resistance,
the Standard requires that straps be installed taut.
B5.4 Diaphragm Design
The Standard does not currently address the design of diaphragms in Canada; however,
pending the completion of research that is currently underway, it is expected that the design
of diaphragms in Canada will be addressed in a future edition.
B5.4.1 General
The Standard permits the use of steel sheet sheathing, concrete or wood structural panels or
other approved materials to serve as the diaphragm sheathing.
B5.4.2 Nominal Strength
The nominal strength of diaphragms is to be based upon principles of mechanics, per
Section B1.2.5.1. Alternatively, for diaphragms sheathed with wood structural panels, the
nominal strength may be determined by Section B5.4.2. The design values for diaphragms
with wood structural panel sheathing in Table B5.4.2-1 were based on work by Lum (LGSEA,
1998). Lum developed ASD design tables using an analytical method outlined by Tissell
(APA, 1993; APA 2000) for wood framing and the provisions of the 1991 NDS (AFPA,
1991). Because steel is not affected by splitting or tearing when fasteners are closely spaced,
no reduction in the calculated strength was taken for closely spaced fasteners. In addition,
although steel with designation thicknesses greater than 33 mil resulted in higher strength
values, no increase in strength was included for these greater thicknesses.
It should be noted that flat strap used as blocking to transfer shear forces between
sheathing panels is permitted, but is not required to be attached to framing members.
It should be noted that the diaphragm design values by Lum were based on the nominal
strength of a No. 8 screw attaching wood structural panels to 33-mil cold-formed steel framing
members. The 1991 NDS calculation methodology, which was used by Lum, yielded a
nominal strength of 372 lbs and a safety factor of 3.3. However, the NDS methodology was
revised in 2001, and the revision greatly reduced the calculated strength of screw
connections. Until Lum's work is updated, justification for maintaining the current
diaphragm design values in the Standard are based, in part, on tests performed by APA
(APA, 2005). Test results for single lap shear tests for a No. 8 screw attaching in.
plywood to 68-mil steel sheet sheathing indicated that the nominal strength [resistance] of the
connection was governed by the strength of the screw in the steel sheet sheathing; i.e., the
wood structural panels did not govern the capacity. Therefore, for thinner steel sheet sheathing,
the limit state would likely be the tilting and bearing failure mode. For a No. 8 screw
installed in 33-mil steel sheet sheathing, computations of connection capacity in accordance
with AISI S100 [CSA S136] would yield a nominal strength of 492 lbs and a safety factor of
3.0. Additionally, connection tests for plywood attached to 33-mil cold-formed steel framing
members were performed by Serrette (1995b) and produced an average ultimate connection
capacity of 1177 lbs, and Serrette suggested the use of a safety factor of 6, as given by APA
E380D. A review of the allowable strengths, as summarized in Table C-B5.4.2-1, indicates
that although Lums design values are based on an earlier edition of the NDS, the value is
conservative when compared to both AISIs and Serrettes results.

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AISI S240-15-C

Table C-B5.4.2-1
No. 8 Screw Shear Strength (lbs) for 33-mil Cold-Formed Steel Member

Lum

AISI 2001

Serrette

Nominal

Allowable

Nominal

Allowable

Nominal

Allowable

372

112

492

164

1177

196

B5.4.4 Design Deflection

The methodology for determining the design deflection of diaphragms was based on a
comparison of the equations used for estimating the deflection of wood frame shear walls
and diaphragms, coupled with similarities in the performance of cold-formed steel and wood
frame shear walls. Collectively, these comparisons suggested that the wood frame diaphragm
equation could be adopted, with modifications to account for the difference in fastener
performance, for application to cold-formed steel light-frame construction. The current
equation for wood frame construction (ICC, 2003) is as follows:
=

( X)
vL
5 vL3
+ 0.188Le n + c
+
2b
8EAb 4Gt

For SI: =
where
A =
b
=
E
=
en =
G =

0.052 vL3 vL Le n ( c X )
+
+
+
EAb
4Gt 1627
2b

(C-B5.4.4-1)
(C-B5.4.4-2)

Area of chord cross-section, in square inches (mm2)

Diaphragm width, in feet (mm)
Elastic modulus of chords, in pounds per square inch (N/mm2)
Nail deformation, in inches (mm)
Modulus of rigidity of wood structural panel, in pounds per square inch
(N/mm2)
L
= Diaphragm length, in feet (mm)
t
= Effective thickness of wood structural panel for shear, in inches (mm)
v
= Maximum shear due to design loads in the direction under consideration, in
pounds per linear foot (N/mm)
= The calculated deflection, in inches (mm)

(cX) = Sum of individual chord-splice values on both sides of the diaphragm, each
multiplied by its distance from the nearest support
Equations C-B5.4.4-1 and C-B5.4.4-2 apply to uniformly nailed, blocked diaphragms
with a maximum framing spacing of 24 inches (610 mm) on center. For unblocked
diaphragms, the deflection must be multiplied by 2.50 (APA, 2001). If not uniformly nailed,
the constant 0.188 (For SI: 1/1627) in the third term must be modified accordingly.
In 2012, coefficients b and in deflection Equation B5.2.5-1 were revised based on
research work by Cobeen (2010). Based on shear wall performance, similar revisions were
made to the deflection Equation B5.4.4-1 for the diaphragm systems.
B5.4.5 Beam Diaphragm Tests for Non-Steel Sheathed Assemblies
Consistent with wood-framed construction, for the in-plane diaphragm, the nominal
shear strength [resistance] is permitted to be determined by a beam test in accordance with
ASTM E455 (2011e). The nominal shear strength is to be the average of a minimum of three
tests in accordance with AISI S100 [CSA S136] Section F1.1(a).

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Commentary on the North American Standard For Cold-Formed Steel Structural Framing, 2015 Edition

The determination of the safety factor and resistance factor, when failure occurs in the
cold-formed steel member or sheathing-to-steel fasteners, is based on the screw connection
statistics from AISI S100 [CSA S136] Chapter F and is consistent with AISI S100 [CSA S136],
Section D6.2.1.
The safety factor of 2.8 and resistance factor of 0.6 are used to be consistent with the wood
sheathing failure as prescribed by the wood industry (AFPA, 2008).
The beam test provides diaphragm performance for an essentially rectangular building
configuration. The aspect ratio of 4:1 reflects the limit for essentially rectangular buildings
as prescribed by AISI S230.

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AISI S240-15-C

C. INSTALLATION
C2 Material Condition
To ensure structural performance is in compliance with the engineered design, structural
members, connectors, hold-downs and mechanical fasteners must not be damaged. Damage
assessment is not within the purview of this Standard. The design professional should be
consulted when damage alters the cross-section geometry of a structural member, or damages to
connectors, hold-downs and mechanical fasteners beyond the specified tolerances.
C2.1 Web Holes
AISI S100 [CSA S136] stipulates design requirements for members with standard web
holes. In the field, these web holes may also be referred to as punchouts, utility holes,
perforations and web penetrations. In structural members, web holes are typically 1.5 in. (38
mm) wide 4 in. (102 mm) long and are located on the center line of the web. The web holes
are generally spaced 24 in. (610 mm) on center.
C2.2 Cutting and Patching
This Standard places restrictions on acceptable methods for cutting of framing members
so that cut edges are not excessively rough or uneven and protective metallic coatings are not
damaged in areas away from cut edges. It is noted that shearing includes a variety of
mechanical methods including, but not limited to, the use of hydraulic shears and hole
punches during manufacturing; and portable hydraulic shears, hand-held electric shears,
aviation snips, and hole punches during fabrication and installation.
Coping, cutting or notching of flanges and edge stiffeners is not permitted for structural
members without an approved design. For guidance on design for coped members in trusses,
refer to Section E4.6.2.
C2.3 Splicing
Structural members may be spliced; however, splicing of studs and joists is not a common
practice and is not recommended. If a structural member requires splicing, the splice connection
must be installed in accordance with an approved design.
C3 Structural Framing
C3.1 Foundation
An uneven foundation may cause problems. The specified in. (6.4 mm) gap has been
deemed acceptable industry practice.
C3.2 Ground Contact
To minimize the potential for corrosion, care must be taken to avoid direct contact
between the cold-formed steel framing and the ground. In addition to direct contact, it is
important to minimize the potential for corrosion resulting from ambient moisture. The
applicable building code is cited as the authoritative document that will provide guidance
concerning minimum separation distances from the ground to the framing member,
installation requirements for moisture barriers, and the necessary ventilation of the space.

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Commentary on the North American Standard For Cold-Formed Steel Structural Framing, 2015 Edition

C3.3 Floors
To avoid premature failure at a support and to achieve in-line framing, full bearing of the
joist on its supporting wall is necessary. The intent of specifying that the track and joist webs
are not to be in direct contact with each other is to prevent floors from creating an unwanted
noise (e.g. squeaks).
C3.4 Walls
C3.4.1 Straightness, Plumbness and Levelness
Wall studs must be installed plumb to avoid the potential for secondary bending
moments in the member. In 2015, a reference to tolerances in ASTM C1007 (ASTM, 2011d)
for plumbness and levelness was added.
C3.4.3 Stud-to-Track Connection
The stud must be nested and properly seated into the top and bottom track to provide
for adequate transfer of forces and minimize axial deflections. Each flange of the stud
should also be attached to the tracks to brace the top and bottom of the stud against weak
axis and torsional displacements.
The maximum end gap specified by this Standard is based on traditional industry
practice. The gap specified in Section C3.4.3(a) is only for axial load bearing walls, which is
defined in Section 202 of the IBC (ICC, 2012) as any metal or wood stud wall that supports
more than 100 pounds per linear foot (1459 N/m) of vertical load in addition to its own
weight.
Axial loads in a wall stud in excess of the capacity of the screw connection between the
stud and its seating tracks will be transferred between the stud and track in bearing. In this
situation, if a stud is not properly seated, relative movement between the stud and the track
may occur, which reduces or closes any gap between the end of the stud and the track.
To determine the influence of this relative movement between the stud and the track on
the serviceability of sheathed wall assemblies, a testing program was conducted at the
University of Missouri-Rolla (Findlay, 2005). The UMR test program only considered the
stud and the track having the same thickness. For thinner stud and track materials (0.054
inches (1.37 mm) or less), testing showed that relative movement between the stud and the
track was accommodated through a combination of track deformation and screw tilting. In
these cases the connection remained intact and was capable of resisting uplift forces and
preventing stud weak axis and torsional displacement. For thicker materials (greater than
0.054 inches), testing showed that the relative movement between the stud and the track
could result in shear failure of the screws. In these cases, testing indicated a smaller end
gap tolerance (e.g., 1/16 inch (1.59 mm)) would be desirable to limit relative movement
and potential screw failure.
In addition to a smaller specified end gap to avoid potential screw failure in track
thicker than 0.054 inches (1.37 mm), a smaller specified gap may also be desirable for
multi-story structures where the accumulation of gap closures may become significant.
Special considerations may also be desirable for heavily loaded cold-formed steel
structures and conditions susceptible to deflections.
One method to help achieve adequate end bearing and minimize undesirable relative
movement between the stud and the track is to specify a smaller 1/16 in. (1.59 mm) gap.
This is a relatively simple criterion to verify. However, not exceeding the 1/16 in.
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AISI S240-15-C

(1.59 mm) gap is on occasion difficult to achieve, particularly with 0.097 in. (2.46 mm) or
thicker track.
Another method to achieve adequate end bearing is to pre-compress the stud inside the
track. This is often accomplished when panelizing the stud walls and pre-compressing the
wall panel before connecting the track to the studs. Wall panelization and pre-compression,
particularly for multi-story cold-formed steel construction, has become a common practice
in several regions of North America. With pre-compression, it can be relatively assured
that the stud will be seated in the track, regardless of the gap after pre-compression. At
present, there are no specific guidelines for the amount of pre-compressive force required
to assure proper seating. Industry practice has been to compress the wall panel until the
studs visually seat inside the radius of the track and before the studs begin to buckle.
Jacking force will vary depending upon the stud size and wall panel height, but is typically
several hundred pounds minimum per stud. Guidelines for verification of proper precompression are nonexistent, but typically pre-compression will result in gaps of 1/16 in.
(1.59 mm) or less for the majority of stud-to-track connections, with no gap exceeding 1/8
inch.
A third method to help ensure adequate end bearing is to oversize the web depth of the
track to minimize any gap. Track oversized 1/16 to 1/8 in. (1.59 mm to 3.18 mm) will
usually have a flat web between the track radii that is greater than the depth of the stud,
enabling the stud to bear directly on the web instead of the track radii. This method will
often be desirable when bearing walls are stick-framed instead of panelized and precompressed. One disadvantage is the oversized track may make a flat wall finish more
difficult.
For all thickness of materials, testing has shown that the gap between the sheathing
and the floor should be equal to or greater than the gap between the stud and the track.
C3.5 Roofs and Ceilings
Proper installation and alignment of roof joists and ceiling joists is necessary to ensure the
proper load transfer from the rafter/ceiling joist connection to the wall framing. To avoid
premature failure at a support and to achieve in-line framing, full bearing of the joist on its
supporting wall framing member or a minimum 1-1/2 inch (38 mm) end bearing is
necessary.
C3.6 Lateral Force-Resisting Systems
Proper installation, consistent with the construction of the tabulated systems that were
tested, is deemed necessary for the performance of the system. Flat strap used as blocking to
transfer shear forces between sheathing panels is permitted, but is not required to be attached
to framing members. For wood structural panel, gypsum board and fiberboard sheathing, screws
must be installed through the sheathing to the blocking. Sheathing screws should be driven to
the proper depth appropriate for the head style used. Bugle, wafer and flat head screws
should be driven flush with the surface of the sheathing; pan head, round head, and hexwasher head screws should be driven with the bottom of the head flush with the sheathing.
See Commentary Section B5.2.2.1 for more discussion on overdriving sheathing screws.

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Commentary on the North American Standard For Cold-Formed Steel Structural Framing, 2015 Edition

C4 Connections
C4.1 Screw Connections
C4.1.2 Installation
Screw length must be adequate to ensure that screw fasteners extend through the steel
connection a minimum of three (3) exposed threads, as illustrated in Figure C-C4.1.2-1.

Figure C-C4.1.2-1 Screw Grip Range

C4.1.3 Stripped Screws

It is unreasonable to expect that there will be no stripped screws in a connection.
Research at the University of Missouri-Rolla (Sokol et al., 1999) has shown that the
structural performance of a single-shear screw connection is not compromised if screws in
the connection have been inadvertently stripped during installation. This research serves as
the basis for the requirements of the Standard.
C4.2 Welded Connections
To maintain acceptable durability of a welded connection, the weld area must be treated
with a corrosion-resistant coating, such as a zinc-rich paint.
C5 Miscellaneous
C5.1 Utilities
C5.1.1 Holes
The design should include references to pre-punch hole sizes or limitations to
accommodate electrical, telecommunication, plumbing and mechanical systems. Field-cut
holes are generally discouraged, but are not uncommon. Field- cut holes, if necessary, are
required to comply with Section C2.1. There are several methods whereby holes can be cut
in the field, such as a hole-punch, hole saws, and plasma cutters.
Holes that penetrate an assembly containing steel framing that has a fire resistance
rating will need to be designed with through-penetration firestop systems. The acceptance
of this fire resistance design is based on the applicable building code.

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AISI S240-15-C

C5.1.2 Plumbing
Direct contact with copper piping should be avoided in order to prevent galvanic
action from occurring. Methods for preventing the contact from occurring may be through
the use of nonconductive and noncorrosive grommets at web penetrations or through the
use of nonmetallic brackets (a.k.a. isolators) fastened to hold the dissimilar metal building
products (e.g. piping) away from the steel framing. Plastic pipe does not require protection
if it is in contact with the cold-formed steel framing member, but consideration should be
made for the installation of nonmetallic brackets to hold the pipe away from the hole in the
steel in order to prevent noise and prevent the steel from cutting into the pipe.
C5.1.3 Electrical
Nonmetallic sheathed wiring must be separated from the cold-formed steel framing
member in order to comply with the National Electrical Code (NFPA, 2011). Contained
within the National Electrical Code is a provision that requires nonmetallic sheathed cable to
be protected by bushings or grommets securely fastened in the opening prior to the
installation of the cable. Cable following the length of a framing member will need to be
secured (e.g., supported) at set lengths; for this purpose, small holes in the web may be
beneficial for the attachment of tie-downs (e.g. nylon cable ties, nylon zipper ties, etc.).
When installing wiring or cables within a framing member (e.g., through or parallel to
member), the intent of the National Electrical Code further requires that the wiring or cables
be located 1-1/4 inches (32 mm) from the edge of the framing member. When 2-1/2-inch
(64-mm)-wide wall studs are used, the restrictions concerning edge clearance apply.
C5.2 Insulation
The cavity insulation must be installed such that the width of the insulation extends from
the face of the web of one framing member to the face of the web of the next framing member.
In the case of cold-formed steel framing, designs should specify full-width insulation in order
to differentiate the insulation that is normally supplied (nominal width).
To enhance the thermal performance of cold-formed steel framed construction, board
insulation (such as continuous insulation or insulating sheathing) may be used in conjunction
with cavity insulation. Guidance on the use of board and batt insulation is given in Thermal
Design and Code Compliance for Cold-Formed Steel Walls (SFA, 2008). Designs should also take
into consideration the effects of moisture when assessing the application of both cavity and
continuous insulation, in this case dew point. The ASHRAE Handbook of Fundamentals
contains information useful for determining dew point (ASHRAE, 2009).

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Commentary on the North American Standard For Cold-Formed Steel Structural Framing, 2015 Edition

D. QUALITY CONTROL AND QUALITY ASSURANCE

D1 General
D1.1 Scope and Limits of Applicability
Chapter D provides minimum requirements for quality control and quality assurance for
material control and installation for cold-formed steel light-frame construction. Minimum
observation and inspection tasks deemed necessary to ensure quality cold-formed steel lightframe construction are specified.
Chapter D does not apply to cold-formed steel nonstructural members. Chapter D does not
apply to the manufacture of cold-formed steel structural members, connectors or hold-downs other
than material control, nor to manufacture of mechanical fasteners or welding consumables.
Chapter D does not address quality control or quality assurance for other materials and
methods of construction.
In Chapter D, material control refers to the general oversight of the materials by the
component manufacturer and installer and involves procedures for storage, release and
movement of materials. Throughout the manufacturing and construction processes,
including the associated inspections, materials are identified and protected from degradation.
Additionally, nonconforming items are identified and segregated as needed.
The Chapter D requirements are patterned after similar requirements developed by the
American Institute of Steel Construction for structural steel and the Steel Deck Institute for
steel deck.
Chapter D defines a comprehensive system of quality control requirements on the part of
the component manufacturer and installer and similar requirements for quality assurance on the
part of the project representatives of the owner when such is deemed necessary to
complement the contractors quality control function. These requirements exemplify recognized
principles of developing involvement of all levels of management and the workforce in the
quality control process as the most effective method of achieving quality in the constructed
product. Chapter D supplements these quality control requirements with quality assurance
responsibilities as are deemed suitable for a specific task.
AISI S202, Code of Standard Practice for Cold-Formed Steel Structural Framing (AISI, 2011),
indicates that the component manufacturer or installer is to implement a quality control system as
part of their normal operations. The registered design professional should evaluate what is
already a part of the component manufacturers or installers quality control system in
determining the quality assurance needs for each project. Where the component manufacturers
or installers quality control system is considered adequate for the project, including
compliance with any specific project needs, the special inspection or quality assurance plan
may be modified to reflect this. Similarly, where additional needs are identified,
supplementary requirements should be specified.
The terminology adopted for use in Chapter D is intended to provide a clear distinction of
component manufacturer and installer requirements and the requirements of others. The
definitions of quality control and quality assurance used here are consistent with usage in
related industries. It is recognized that these definitions are not the only definitions in use.
For the purposes of this Standard, quality control includes those tasks performed by the
component manufacturer and installer that have an effect on quality or are performed to
measure or confirm quality. Quality assurance tasks performed by organizations other than
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AISI S240-15-C

the component manufacturer and installer are intended to provide a level of assurance that the
product meets the project requirements. The terms quality control and quality assurance are
used throughout Chapter D to describe inspection tasks required to be performed by the
component manufacturer and installer and representatives of the owner, respectively. The quality
assurance tasks are inspections often performed when required by the applicable building code or
authority having jurisdiction, and designated as special inspections, or as otherwise required
by the project owner or registered design professional.
D1.2 Responsibilities
The requirements in Chapter D are considered adequate and effective for most cold-formed
steel light-frame construction.
Where the applicable building code and authority having jurisdiction require the use of a
quality assurance program, Chapter D outlines the minimum requirements deemed effective to
provide satisfactory results in cold-formed steel light-frame construction. There may be cases
where supplemental inspections are advisable. Additionally, where the contractors quality
control program has demonstrated the capability to perform some tasks that this plan has
assigned to quality assurance, modification of the plan could be considered.
D2 Quality Control Programs
Many quality requirements are common from project to project. Many of the processes used
to produce cold-formed steel light-frame construction have an effect on quality and are fundamental
and integral to the component manufacturers or installers success. Consistency in imposing
quality requirements between projects facilitates more efficient procedures for both. The
construction documents referred to in Chapter D are, of necessity, the versions of the plans,
specifications, and approved shop drawings and approved installation erection drawings that have been
released for construction, as defined in AISI S202. When responses to requests for information
and change orders exist that modify the construction documents, these are also part of the
construction documents. When a building information model is used on the project, it is also a
part of the construction documents.
Elements of a quality control program can include a variety of documentation such as
policies, internal qualification requirements, and methods of tracking production progress. Any
procedure that is not apparent subsequent to the performance of the work should be considered
important enough to be part of the written procedures. Any documents and procedures made
available to the quality assurance inspector should be considered proprietary and not distributed
inappropriately.
The inspection documentation should include the following information:
(1) The product inspected
(2) The process that was conducted
(3) The name of the inspector and the time period within which the inspection was
conducted
(4) Non-conformances and corrections implemented
Records can include marks on pieces, notes on drawings, process paperwork, or electronic
files. A record showing adherence to a sampling plan for pre-welding compliance during a
given time period may be sufficient for pre-welding observation inspection.
The level of detail recorded should result in confidence that the product is in compliance
with the requirements.

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Commentary on the North American Standard For Cold-Formed Steel Structural Framing, 2015 Edition

D3 Quality Control Documents

D3.1 Documents to be Submitted
The documents listed must be submitted so that the registered design professional can
evaluate that the items prepared by the component manufacturer or installer meet the registered
design professionals design intent. This is usually done through the submittal of shop drawings
and installation drawings. In many cases digital building models are produced in order to
develop shop drawings and installation drawings. In lieu of submitting shop drawings and
installation drawings, the digital building model can be submitted and reviewed by the
registered design professional for compliance with the design intent. For additional information
concerning this process, refer to the AISC Code of Standard Practice for Steel Buildings and
Bridges Appendix A, Digital Building Product Models.
The exception in Section D3.1.1.3 limits the additional requirements in Sections D3.1.1.1
and D3.1.1.2 to lateral force-resisting systems with relatively high capacities.
D3.2 Available Documents
The documents listed must be made available for review by the registered design
professional. In some instances, the registered design professional may require the submittal of
additional documents. Certain items are of a nature that submittal of substantial volumes of
documentation is not practical, and therefore it is acceptable to have these documents
reviewed at the component manufacturers or installers facility by the registered design
professional or quality assurance agency. Additional commentary on some of the
documentation listed in this section is as follows:
(a) Documents related to connectors, hold-downs and mechanical fasteners are required only
in cases where connectors, hold-downs and mechanical fasteners are being installed.
(b) Documents related to welding are required only in cases where welding of cold-formed
steel structural members is being performed.
(c) Specific welders may not be known until installation begins; therefore, welding
personnel performance qualification records may not be made available until
immediately before installation begins.
(d) Because the selection and proper use of welding filler metals is critical to achieving the
necessary levels of strength and quality, the availability for review of welding filler
metal documentation and welding procedure specifications (WPSs) is required. This
allows a thorough review on the part of the registered design professional, and allows the
registered design professional to have outside consultants review these documents, if
needed.
(e) The component manufacturer and installer maintain written records of welding personnel
qualification testing. Such records should contain information regarding date of
testing, process, welding procedure specifications, test plate, position, and the results
of the testing. In order to verify the six-month limitation on welder qualification, the
component manufacturer and installer should also maintain a record documenting the
dates that each welder has used a particular welding process.

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AISI S240-15-C

D5 Inspection Personnel
D5.1 Quality Control Inspector
The component manufacturer or installer determines the qualifications, training and
experience required for personnel conducting the specified inspections. Qualifications should
be based on the actual work to be performed and should be incorporated into the component
manufacturers or installers quality control program. Inspection of welding should be performed
by an individual who, by training and/or experience in metals fabrication, inspection and
testing, is competent to perform inspection of the work. Recognized certification programs are
a method of demonstrating some qualifications, but they are not the only method nor are
they required by Chapter D for quality control inspectors.
D5.2 Quality Assurance Inspector
The quality assurance agency determines the qualifications, training and experience
required for personnel conducting the specified quality assurance inspections. This may be
based on the actual work to be performed on any particular project. Qualification for the
quality assurance inspector may include experience, knowledge and physical requirements.
These qualification requirements are documented in the quality assurance agencys written
practice. AWS B5.1 (AWS, 2003) is a resource for qualifications of a welding inspector.
D6 Inspection Tasks
D6.1 General
Chapter D defines two inspection levels for required inspection tasks and labels them as
either observe or perform. This is in contrast to common building code terminology
which uses or has used the terms periodic or continuous. However, this is consistent
with the AISC and SDI standards that were used as a pattern for this Standard.
The tables in Sections D6.5 through D6.9 list the required inspection tasks for quality control
and quality assurance. If inspections identify nonconforming material or workmanship, the
need for additional inspections and rejection of material is to be assessed in accordance with
Section D7.
The tables in Sections D6.5 through D6.9 also list the required documentation tasks for
quality assurance. Documentation tasks for quality control are not required by Chapter D, but
should be as defined by the applicable quality control program of the component manufacturer or
installer.
D6.2 Quality Control Inspection Tasks
Quality control documentation is an internal record for the component manufacturer or
installer to record that the work has been performed and that the work is in accordance with
the shop drawings or construction documents, as applicable. Depending upon the component
manufacturers or installers quality control program, the method of documentation may vary.
Model building codes, such as the International Building Code (ICC, 2015), often make
specific statements about performing inspections to approved construction documents. AISI S202
requires the transfer of information from the contract documents into accurate and complete
shop drawings and installation drawings. Therefore, relevant items in the plans and specifications
that must be followed in component manufacturing and installation should be placed on the
shop drawings and installation drawings, or in typical notes issued for the project. Because of
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Commentary on the North American Standard For Cold-Formed Steel Structural Framing, 2015 Edition

this provision, quality control inspection may be performed using shop drawings and installation
drawings, not the original plans and specifications.
D6.3 Quality Assurance Inspection Tasks
Model building codes, such as the International Building Code (ICC, 2015), make specific
statements about performing inspections to approved construction documents. Accordingly, the
quality assurance inspector should perform inspections using the original plans and specifications.
The quality assurance inspector may also use the shop drawings and installation drawings to assist
in the inspection process.
D6.4 Coordinated Inspection
Coordination of inspection tasks may be needed for component manufacturers in remote
locations or distant from the project itself, or for installers with projects in locations where
inspection by a local firm or individual may not be feasible or where tasks are redundant. The
approval of both the authority having jurisdiction and registered design professional is required
for quality assurance to rely upon quality control, so there must be a level of assurance provided
by the quality activities that are accepted.
D6.5 Material Verification
Compliance of cold-formed steel structural members typically includes verification of
product identification in accordance with Section A5.5 and shape dimensions and sizes in
accordance with an approved design or approved design standard. The manufacturer of coldformed steel structural members is typically responsible for verification of material in
accordance with Section A3, corrosion protection in accordance with Section A4, and base steel
thickness in accordance with Section A5.1.
The installer should consider Section G1.1 of AISI S202 when establishing material control
procedures for cold-formed steel structural members. Coldformed steel structural members that
lack product identification are typically tested to determine conformity.
D6.6 Inspection of Welding
Compliance of welds typically includes verification of weld size, length and location.
D6.7 Inspection of Mechanical Fastening
Compliance of mechanical fasteners typically includes verification of mechanical fastener
type, diameter, length, quantity, spacing, edge distance and location.
D6.8 Inspection of Cold-Formed Steel Light-Frame Construction
Compliance of cold-formed steel light-frame construction typically includes verification
of component assembly, structural member and connector sizes and locations; bracing,
blocking and bearing stiffener sizes and locations; and bearing lengths.
D6.9 Additional Requirements for Lateral Force-Resisting Systems
Compliance of cold-formed steel lateral force-resisting system installation typically includes
verification of shear walls; diagonal strap bracing and gusset plates; hold-downs and anchor bolts;
collectors (drag struts); and diaphragms.
The exception in Section D6.9 limits the additional requirements to lateral force-resisting
systems with relatively high capacities.
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AISI S240-15-C

In Table D6.9-2, a welder identification system is a system maintained by the component

manufacturer or installer, as applicable, by which a welder who has welded a joint or member
can be identified.

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Commentary on the North American Standard For Cold-Formed Steel Structural Framing, 2015 Edition

E. TRUSSES
E1 General
E1.1 Scope and Limits of Applicability
Cold-formed steel trusses are planar structural components. Structural performance
depends on the trusses being installed vertically, in-plane, and at specific spacing, and being
properly fabricated and braced. The Standard describes the materials used in a cold-formed
steel truss, as well as design, fabrication, and bracing procedures for truss members.
This Standard is intended to serve as a supplement to AISI S100 [CSA S136], (AISI, 2012a;
CSA, 2012). The provisions provided in Chapter E are also intended to be used in conjunction
with the other chapters of the Standard.
E2 Truss Responsibilities
The Standard adopts Section I1 of AISI S202 (AISI, 2011a) for the responsibilities of the
individuals and organizations involved in the design, fabrication and installation of cold-formed
steel trusses. Alternate provisions as agreed upon by the involved parties are permitted.
E3 Loading
The Standard does not establish the appropriate loading requirements for which a truss
should be designed. In most cases, these loads are adequately covered by the applicable building
code or standard.
E4 Truss Design
The provisions contained in this section of the Standard address the various design aspects
related to truss strength [resistance]. The strength [resistance] determinations required by the
Standard are in accordance with either the Allowable Strength Design (ASD), Load and Resistance
Factor Design (LRFD) or Limit States Design (LSD) methods given by AISI S100 [CSA S136], (AISI,
2012; CSA, 2012), except where additional research studies have indicated an alternative
approach is warranted.
E4.3 Analysis
The structural analysis requirements contained in the Standard are based on available
information pertaining to the behavior of cold-formed steel C-shaped section truss assemblies
(Harper, 1995; LaBoube and Yu, 1998). These requirements do not preclude the use of more
rigorous analysis or design assumptions as determined by rational analysis or testing.
E4.4 Member Design
E4.4.1 Properties of Sections
AISI S100 [CSA S136] has been shown to be highly reliable for determining the design
cross-section properties of C-shapes and other simple geometries. For more complex shapes,
such as those utilizing longitudinal stiffeners, AISI S100 [CSA S136] Direct Strength
Method design provisions may be used to estimate the load-carrying capacity. Tests in
accordance with Section F1 of AISI S100 [CSA S136] can also be used.

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AISI S240-15-C

E4.4.2 Compression Chord Members

When subjected to gravity load, the compression chord member may experience the
combined effects of bending and axial compression. The design for combined load effects
is governed by Section C5.2 of AISI S100 [CSA S136].
Engineering design specifications recognize the need for using rational analysis or test
to define an effective length factor. The Standard permits the use of either rational analysis
or testing.
Based on research on C-shaped section trusses conducted at the University of MissouriRolla (UMR) (Harper, 1995; Ibrahim, 1998), it was determined that the unbraced lengths, Lx
and Lt, may be taken as equal to the distance between the panel points. It was also
discovered that where structural sheathing is attached to the chord member and where the
compression chord member is continuous over at least one intermediate panel point, and is
continuous from the heel to the pitch break, heel to heel (in the case of a parallel chord truss),
or breakpoint of a truss, Ly may be taken as the distance between sheathing connectors.
Engineering judgment indicates that where sheathing is not attached to the top chord
member, Ly may be taken as the distance between panel points.
In the cold-formed steel truss industry, the sheathing is used as a structural component
and the connection spacing of the sheathing to the cold-formed steel member is a design
consideration. Therefore, sheathing connector spacing is indeed a structural requirement,
and that is why the spacing of the connector is used when designing the truss chords for
compression when there is structural sheathing applied.
The UMR research also determined that for a structurally sheathed C-shaped section
truss where the compression chord member is continuous over at least one intermediate
panel point, and is continuous from the heel to the pitch break, or breakpoint of a truss, Kx,
Ky, and Kt may be taken as 0.75. For other compression chord members, based on
engineering judgment, Kx, Ky, and Kt should be taken as unity.
An alternative design assumption for chord members in compression, based on
engineering practice and judgment, is to assume that the effective length be taken as the
distance between two adjacent points of contraflexure. In such case, the effective length
factor and Cm should be taken as unity.
The required effective length factors and unbraced lengths given in the Standard for
hat-shapes are based on engineering judgment. The Z-shape requirements are based on
proprietary testing.
Consistent with AISI S100 [CSA S136], the end moment coefficient, Cm, should be taken
as 0.85, unless a more rigorous analysis is performed to justify another value.
Requirements in the Standard for the evaluation of the bending strength [resistance]
are based on engineering judgment.
Ibrahim et al. (1998)- determined that when a C-shaped section compression chord
member is subject to concentrated load at a panel point, the interaction of axial
compression, bending and web crippling must be considered. The researchers proposed the
following ASD interaction equation:
P
M
R 1.49
(Eq. C-E4.4.2-1)
+
+

Pno M nxo R n

where
P
= Compression axial load
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Commentary on the North American Standard For Cold-Formed Steel Structural Framing, 2015 Edition

M = Bending moment
R
= Concentrated load
Pno = Nominal axial strength [resistance] computed at f = Fy
Mnxo= Nominal flexural strength [resistance] computed at f = Fy
Rn = Nominal interior one-flange web crippling strength [resistance]
= Safety factor
= 1.95
The values of P and M are to be determined by structural analysis for the panel point in
question, where R is the applied concentrated load at the panel point. The nominal strengths
[resistances] are to be computed using AISI S100 [CSA S136]. Based on a statistical analysis
consistent with load and resistance factor design, the safety factor was determined. The
Standard also includes a similar equation applicable to the LRFD and LSD methods.
E4.4.3 Tension Chord Members
The design requirements prescribed by the Standard for tension chord members are
based on experience and engineering judgment.
E4.4.4 Compression Web Members
The behavior of a compression web member is a function of the connection of the web
member to the chord member. For example, a common connection detail of C-shaped chord and
web members is to attach the respective members back-to-back through their webs. Such a
connection detail creates an eccentric loading condition in the web member. When an axial
load is applied to a truss web member in this type of truss construction, this eccentric loading
condition will produce a bending moment in the member that is acting out-of-plane to the
truss. This bending moment needs to be analyzed using Section E4.4.4 of this Standard. In
addition to the check in this Standard, a compression web member is to be analyzed with the
axial load alone using Section C4 of AISI S100 [CSA S136].
Researchers at the University of Missouri-Rolla (Rieman, 1996; Ibrahim et al., 1998)
determined that for a C-shaped compression web member that is attached through its web
element, the interaction of axial compression and out-of-plane bending may be determined
by the following ASD interaction equation:
c RP b C my RPe
(C-E4.4.4-1)
+
1.0
Pn
M ny y
where
2

L /r
L /r
0.22 0.6
R =
(C-E4.4.4-2)
+
88
173
L = Unbraced length of the compression web member
r = Radius of gyration of the full section about the minor axis
Pn = Nominal axial strength [resistance] based on Section C4.1 of AISI S100 [CSA S136].
Only flexural buckling need be considered.
e = Eccentricity of compression force with respect to the centroid of the full section
of the web member
Other variables are defined in Section C5.2.1 of AISI S100 [CSA S136].
The parameter, R, is an experimentally determined reduction imposed on the axial
load. The equation is a fit to the average test data, which is a common practice in coldformed steel research. To recognize the lower limit on the tested L/r ratio, the Standard
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AISI S240-15-C

stipulates R 0.6. The intent of R is to recognize the increased significance of the bending
effect, compared to the axial effect for longer length web members. Unique to the application
of the interaction equation is the determination of the nominal axial strength [resistance]
based on flexural buckling alone. Research showed that the minor axis bending, which
resulted from the eccentrically applied axial load, created a member deflection that enabled
only flexural buckling. Thus, the behavior of the web member was determined
predominately by bending resulting from the eccentric load. The parameters P, b, c,
Cmy, Mny and y are defined in accordance with Section C5.2.1 of AISI S100 [CSA S136].
The Standard also includes a similar equation applicable to the LRFD and LSD methods.
For compression web member cross-sections other than a C-shape attached through its
web element, which has symmetry of loading, the axial compression load may be taken as
acting through the centroid of the section.
When computing the available strength [factored resistance], the effective lengths, KxLx,
KyLy and KtLt, may be taken as the distance between the centers of the members end
connection patterns. This assumption is consistent with the analysis approach used by UMR
researchers (Rieman, 1996; Ibrahim et al., 1998).
E4.4.5 Tension Web Members
Tension web members may experience a reduction in load-carrying capacity when
subjected to combined axial load and bending. For C-shaped sections, this may be attributed
to the dominant behavior being that of bending resulting from the eccentric load.
However, testing has not documented that the combined loading compromises the
integrity of the tension member. Therefore, for a tension web member connected to the web
element of a chord member, or connected to a gusset plate, the Standard permits the axial
tension load to be taken as acting through the centroid of the web member's cross-section.
E4.4.6 Eccentricity in Joints
The Standard does not specify the use of a multiple or single node structural analysis
model to account for the effects of eccentricity in joints. The truss stiffness will differ based
on whether a multiple or single node analysis is performed. When a multiple node analysis
is used, a node should be placed at each web member location where the center line of the
web member meets the center line of the chord member. When performing a single node
analysis, additional design considerations may be necessary. For example, eccentricity
created by the spatial relationship of the web members and the chord member at a joint may
generate additional moments, shears, and/or axial forces. Such moments and forces may
be directly reflected in a multiple node analysis model. Thus, when using a single node
analysis model, a secondary analysis and design check of the joint, or a load test may be
required to justify the design.
The Standard defines a web member lap length as 75% of the chord member depth. This
minimum lap length is assumed, based on engineering judgment, to serve as a web shear
stiffener for the chord member. The chord member segment between the assumed stiffeners is
to be investigated for combined bending and shear, where a stiffened shear panel is
assumed, in accordance with Equation C3.3.1-2 of AISI S100 [CSA S136]. For truss
configurations having the web member lap length less than 75% of the chord members depth,
the chord member is to be investigated for combined bending and shear in accordance with
Equation C3.3.1-1 of AISI S100 [CSA S136]. Refer to Figures C-E4.4.6 (a) and C-E4.4.6 (b) for
a pictorial definition of the term web member lap length for two configurations of a truss
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Commentary on the North American Standard For Cold-Formed Steel Structural Framing, 2015 Edition

web member and truss chord member connection. Rational design assumptions for this web
member lap length must be used when other connection geometries are encountered.
Along the length of the chord member, at the mid-point between the intersecting web
members, shear is to be evaluated by Section C3.2 of AISI S100 [CSA S136]. The shear buckling
coefficient is taken to be consistent with the assumed shear panel condition at the segments
ends as defined by Section C3.2 of AISI S100 [CSA S136].
Based on experience, where screws are used as the connector, a minimum of four
screws should be used in a web member to chord member connection and the screws should be
equally distributed in their group.

(a) Web Member Lap Length for Flat Truss Chord

(b) Web Member Lap Length for Sloped Truss Chord

Figure C-E4.4.6 Web Member Lap Lengths

E4.5 Gusset Plate Design

To establish a design methodology for thin gusset plate connections in compression, a
testing program consisting of 49 specimens was conducted at the University of MissouriRolla (Lutz, 2004). Two separate models were developed to predict the capacity of the plates.
Both plate buckling and column buckling models were studied. Although both models are
sufficient for calculating the strength [resistance] of the gusset plates, it was recommended that
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AISI S240-15-C

the plate-buckling model be used in design. The plate-buckling model, assuming f=Fy, k=4
and w=Wmin, provided a better correlation to the test data. A limited number of tests were
performed to determine the strength gain in gusset plates with edge stiffeners. The results of
tests in which both edges of the gusset plate parallel to the applied load had edge stiffeners
showed an approximate strength increase of 25% for the plates.
The gusset plate design provisions in the Standard require that Wmin be taken as the lesser
of the actual gusset plate width or the Whitmore section, which defines a theoretically effective
cross-section based on a spread-out angle of 30 along both sides of the connection, beginning
at the first row of fasteners in the connection. The first row of fasteners is defined as the row of
fasteners that is the furthest away from the section of gusset plate being considered. Figure CE4.5-1 illustrates how Wmin can be determined for a typical fastener pattern connecting a
truss chord member to a gusset plate at a typical pitch break connection at the ridge of a roof truss.
Determining Wmin for other conditions would be analogous.

first row of
fasteners

Whitmore
section

30
truss member
Figure C-E4.5-1 Whitmore Plate Width

The gusset plate design provisions in the Standard require that Leff be taken as the average
length between the last rows of fasteners of adjacent truss members. Figure C-E4.5-2
illustrates how Leff can be determined for a typical pitch break connection at the ridge of a roof
truss. Determining Leff for other conditions would be analogous.
For gusset plates in tension, reference is made to the requirements of AISI S100 [CSA S136].
These requirements include checks on the gross and net areas of the gusset plate, shear lag and
group or tear-out of fasteners. Engineering judgment is required to determine the portion of
the gusset plate to be included in the gross and net area checks.

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Commentary on the North American Standard For Cold-Formed Steel Structural Framing, 2015 Edition

last row of
fasteners

Leff

truss member
(a) Without King Post

last row of
fasteners

Leff

last row of
fasteners

truss web
member
truss chord member
(b) With King Post
Figure C-E4.5-2 Effective Length for Typical Pitch Break Connection

E4.6 Connection Design

E4.6.1 Fastening Methods
Although the common fastening system used by the industry is the self-drilling screw,
the Standard permits the use of bolts, welds, rivets, clinches, and other technologies as
approved by the truss designer. Screw, bolt, and weld connections are to be designed in
accordance with AISI S100 [CSA S136]. If other fastener types, such as rivets, clinches,
rosettes, adhesives, etc., are to be used in the fabrication of the truss, the design values are
to be determined by tests, and the available strength [factored resistance] determined in

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AISI S240-15-C

accordance with Section F1 of AISI S100 [CSA S136].

For the design of connecting elements, such as plates, gusset plates, and brackets,
reference is made to AISI S100 [CSA S136], which in turn makes reference to Section J4 of
AISC 360 (AISC, 2010).
E4.6.2 Coped Connections for C-Shaped Sections
The design engineer should give special attention to the heel and pitch break connections
of the truss to ensure structural integrity of the truss.
At a pitch break, coped members may be reinforced to prevent web buckling of the chord
member. Attachment of a track section of the same thickness as the chord member, thus
creating a box section, and having a length equal to the depth of the chord member has been
shown to provide adequate reinforcement (Ibrahim, 1998). Lateral bracing is also important
to stabilize the pitch break from overall buckling. At the heel, a bearing stiffener may be
needed to preclude web crippling (Koka, 1997).
At a heel connection, UMR research (Koka, 1997) determined that coping reduces both
the shear buckling and web crippling strength [resistance] of the coped bottom chord member.
The UMR research proposed that where a coped flange had a bearing stiffener with a
minimum moment of inertia (Imin) of 0.161 in.4 (67,000 mm4), the shear strength
[resistance] could be calculated in accordance with AISI S100 [CSA S136] Section C3.2, but
required a reduction as defined by the following factor, R:
0.556c 0.532d c
(C-E4.6.2-1)
R = 0.976 +

1.0
h
h
The cited limits in the Standard reflect the scope of the experimental study and apply
only to connections where the bottom chord member is coped.
Where a bearing stiffener not having the minimum moment of inertia is used, web
crippling controlled the heel connection strength [resistance] (Koka, 1997). Therefore, the
Standard requires that the computed end one-flange loading web crippling strength
[resistance] at the heel, as determined by AISI S100 [CSA S136] Section C3.4 be reduced by
the following factor:
0.668c 0.0505d c
(C-E4.6.2-2)
R = 1.036 +

1 .0
h
h
The cited limits in the Standard reflect the scope of the experimental study.
Where c = length of cope and dc = depth of cope as illustrated in Figure C-E4.6.2-1. Imin
of the stiffener is computed with respect to an axis parallel to the web of the bottom chord
member.

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Commentary on the North American Standard For Cold-Formed Steel Structural Framing, 2015 Edition

Depth of cope

Length of cope

Figure C-E4.6.2-1 Definition of Truss Coping Dimensions

E4.7 Serviceability
Serviceability limits are to be chosen based on the intended function of the structure, and
should be evaluated based on realistic loads and load combinations as determined by the
building designer. Because serviceability limits depend on the function of the structure and the
perception of the occupant, it is not possible to specify general limits in the Standard. As a
guide to the designer, the maximum allowable deflection of the chord member of a truss resulting
from gravity load, excluding dead load, may be taken as the following:
(a) Span/360 for plaster ceilings
(b) Span/240 for flexible type ceilings
(c) Span/180 for no finished ceiling
(d) Span/480 for floor systems
Although the use of a deflection limit has been used to preclude vibration problems in the
past, some floor systems may require explicit consideration of the dynamic characteristics of
the floor system.
Truss serviceability is evaluated at nominal [specified] load. When computing truss
deflections, the Standard permits the use of the full cross-sectional area of the truss members.
The use of full areas is warranted because a truss system is a highly indeterminate structural
system, and local buckling of an individual member does not appreciably affect the stiffness
of the truss at design load.
E5 Quality Criteria for Steel Trusses
The practices defined herein have been adopted by the Standard as commonly accepted
practice. In the absence of other instructions in the contract documents, the provisions of
Chapter E4 are the quality standard for the manufacturing processes of steel trusses to be used
in conjunction with an in-plant quality assurance procedure and a truss design.

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AISI S240-15-C

E6 Truss Installation
Cold-formed steel trusses are planar structural components. The structural performance
depends on the trusses being installed vertically, in-plane, at specified spacing, and being
properly braced. The installer is responsible for receipt, storage, erection, installation, field
assembly, and bracing. The practices defined herein have been adopted by the Standard as
commonly accepted practice.
A maximum bottom chord permanent lateral restraint and brace spacing of 10 feet is
suggested, based on field experience and limited testing.
E6.1.1 Straightness
The truss installation tolerances defined in Section E6.1.1 have been used for many
years in the prefabricated truss industries of both cold-formed steel and wood with good
success. The tolerances listed in this section are truss assembly tolerances and not
individual member tolerances. Member tolerances are outlined in the Standard. Coldformed steel trusses are typically used with structural sheathing applied to the top chord.
This sheathing is designed to support lateral loads and act as a diaphragm. This
diaphragm system behavior for trusses with the structural sheathing is what also enables
the adoption of a seemingly more liberal out-of-straightness.
E6.1.2 Plumbness
The truss installation tolerances defined in Section E6.1.2 have been used for many
years in the prefabricated truss industries of both cold-formed steel and wood trusses.
E7 Test-Based Design
Design calculations require the application of approved materials and cross-section
properties. When calculations are used to define the structural performance of a truss assembly,
the structural performance may be verified by full-scale test. However, when the structural
performance cannot be determined by calculation, the structural performance must be
determined by test. Appendix 2 of this Standard provides guidance for both component and
full-scale load tests.

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Commentary on the North American Standard For Cold-Formed Steel Structural Framing, 2015 Edition

F. TESTING
In 2015, Chapter F was created to allow reference to applicable AISI S900-series test
standards.
F1 General
Section F1 lists all the AISI S900-series test standards that are deemed to be generally
applicable to cold-formed steel structural framing applications.
F2 Truss Components and Assemblies
In 2015, methods for testing truss components and assemblies, formerly in AISI S214
Chapter G, were moved to Appendix 2.

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AISI S240-15-C

APPENDIX 1, CONTINUOUSLY BRACED DESIGN FOR DISTORTIONAL BUCKLING

RESISTANCE
Calculation of the nominal distortional buckling strength in flexure and in compression in
accordance with AISI S100 [CSA S136] may utilize the beneficial system effect of sheathing
fastened to the compression flange(s) of floor joists, ceiling joists, and roof rafters through the
calculation of the rotational stiffness provided to the member, k. It is also permissible, and
indeed conservative, to ignore this beneficial restraint and assume k=0.
Testing was conducted to determine the provided rotational restraint in typical framing
systems (Schafer et al. 2007, 2008). From this testing it was determined that the sheathing
rotational restraint could be divided into two parts: one from the sheathing and one from the
connector. For the sheathing industry, standard values as provided by the APA, Panel Design
Specification (APA, 2004) and the Gypsum Association (GA, 2001) are provided. As reported in
Schafer et al. (2007, 2008), the gypsum board provided stiffness in-line with or exceeding
reported values; but the deformation capacity was severely limited; therefore, it was
determined that gypsum board should only be relied upon in a serviceability check, not for
strength limit states. Currently, only the Direct Strength Method of AISI S100 Appendix 1
provides a serviceability methodology for distortional bucking; therefore, the design method
specifically references Appendix 1 for checking serviceability with gypsum board. For the
connector, the experimentally determined values are fit to a simple empirical expression and
then provided in tabular form. The testing was conducted with fasteners at 12 in. (305 mm) o.c.;
therefore, the Standard requires that this fastener spacing (or less) be maintained.
Design examples and design aids for the application of these methods to floor joists are
provided in CFSEI Technical Note G100-08 (Schafer, 2008).

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Commentary on the North American Standard For Cold-Formed Steel Structural Framing, 2015 Edition

APPENDIX 2, TEST METHODS FOR TRUSS COMPONENTS AND ASSEMBLIES

2.1 Component Structural Performance Load Test
The load test procedures contained in the Standard may be used to confirm or define the
design methodology for a chord member or a web member of a truss assembly. This test protocol is
intended for use in the testing of truss assembly components fabricated using cold-formed steel
structural members.
Because the flexural strength [resistance] of a truss member may be bending (yielding or
buckling), shear, web crippling, or combinations thereof, this test protocol defines what should
be considered in regard to a test, but does not define for the testing agency how to do the test.
This leaves the selection of the test fixture and loading medium to the discretion of the testing
agency. For details of test apparatus and procedures that have been used for such purposes, but
in no way should be regarded as mandatory, see Hetrukul and Yu (1978), LaBoube and Yu
(1978a, 1978b, 1982), and Yu (2000).
This protocol also outlines the procedures to be followed to define the compression strength
[resistance] of a truss component for static load. Because the compression strength [resistance] of
a truss component may be local buckling or overall column buckling, this procedure defines
what to do in regard to performing a test, but does not tell the testing agency how to do the test.
This leaves the selection of the test fixture and loading medium to the discretion of the testing
agency. It is the responsibility of the design professional to determine the appropriate loading
rate.
Load tests can be hazardous to the individuals performing or observing the tests, and also
can damage the testing fixtures or the structure housing the test setup due to a sudden release
of stored energy at failure. Care should be exercised in the preparation of the test setup to
ensure that the failure of a test specimen will not result in a secondary collapse of a structural
element not involved in the test.
The number of similar components that should be tested will vary with the desired
precision and reliability of the information to be obtained and with the purpose of the test.
Loads may be measured using one or more of the following devices. Pressure gages or load
cells can be incorporated into a hydraulic loading system. These devices must be calibrated with
the jacks or cylinders at different positions of piston travel to ensure a true loading history.
Deflection readings may be taken in a variety of ways. One of the simplest methods is by the
use of a taut wire or monofilament line stretched between supports in combination with a
mirror-scale located at the desired deflection measurement points. When the taut wire method
is used, care must be taken to ensure that the wire will remain under tension during the entire
test. This can be accomplished by incorporating a spring into the line or by letting one end run
over a pulley with a weight attached to the line. Deflections are read on a scale with a mirror
backing. The mirror-scale deflection measurement device is read by visually lining up the top of
the wire with its image on the mirror and then reading the scale.
Other commonly used deflection measurement devices are such things as direct reading
micrometer dial gages, optical levers used to read scales attached to the truss, linearly variable
differential transformers (LVDT), or a combination of flexible wire attached at deflection points
and monitored remotely through a system of pulleys attached to dial gages.
2.2 Full-Scale Confirmatory Load Test
This test protocol is intended for use in the testing of truss assemblies fabricated using coldThis document is copyrighted by AISI. Any redistribution is prohibited.

AISI S240-15-C

formed steel structural members and connections. A confirmatory test is performed with the intent
to verify structural performance as defined by calculations in accordance with a recognized
specification or standard. Because design was in accordance with a specification or standard, all
that is needed is that the tested specimen demonstrates strength [resistance] not less than the
applicable calculated strength [resistance].
The test protocol does not purport to address all of the safety problems associated with its
use. It is the responsibility of the user of this protocol to establish appropriate safety and health
practices and determine the applicability of regulatory limitation prior to use.
A full-scale truss test is the test of a structural system. It is generally accepted that a safety
factor of 1.5 is for overload and nothing above it should be expected in an in-situ test since the
other uncertainties may already have been used up. If the test is conducted under laboratory
conditions, 1.65 is a reasonable safety factor since fabrication and erection uncertainties are
minimized. This factor of 1.65 is consistent with the recommendations of the Steel Joist Institute.
This protocol outlines the procedures to be followed in the static load testing of loadcarrying truss assemblies. While the procedure tells what to do, it does not tell the testing
agency how to do it. This leaves the selection of the test fixture and loading medium to the
discretion of the testing agency. It is the responsibility of the design professional to determine the
appropriate loading rate.
Full-scale load tests of any large-size specimen such as a truss can be hazardous to the
individuals performing or observing the tests, and also can damage the testing fixtures or the
structure housing the test setup due to a sudden release of stored energy at failure. Care should
be exercised in the preparation of the test setup to ensure that the failure of a test specimen will
not result in a secondary collapse of a structural element not involved in the test.
The test fixture and load application means should be designed with adequate strength
[resistance] and stiffness to ensure that it is the test specimen that is being tested and not the test
fixture.
In a single truss test, frequently the support at one end will allow rotation but not translation
(a rocker) and the other will allow both rotation and translation (a roller) so as not to induce
additional unintentional secondary stresses into the test truss as it deforms under load.
The loading devices should result in the desired truss-loading situation regardless of
whether uniform, concentrated, or a combination of both. The loading system should be such as
to allow the application of loads during the test to approximate the overall intended in-service
load distribution. Care should be taken to avoid eccentrically applied loads unless this type of
loading is desired.
2.3 Full-Scale Structural Performance Load Test
This test protocol is intended for use in the testing of truss assemblies fabricated using coldformed steel structural members and connections when calculation of the safe strength [resistance]
cannot be made in accordance with recognized calculation design specifications or standards.

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Commentary on the North American Standard For Cold-Formed Steel Structural Framing, 2015 Edition

REFERENCES
(AFPA, 2005a), National Design Specification for Wood Construction, American Forest and
Paper Association, Washington, DC, 2005.
(AFPA, 2005b), Special Design Provisions for Wind and Seismic, SDPWS-2005, American Forest
and Paper Association, Washington, DC, 2005.
(AFPA, 1997), National Design Specification for Wood Construction, American Forest and
Paper Association, Washington, DC, 1997.
(AFPA, 2001), Manual for Engineered Wood Construction, Wood Structural Panels Supplement,
American Forest and Paper Association, Washington, DC, 2001.
(AFPA, 1995), Wood Frame Construction Manual for One- and Two-Family Dwellings, American
Forest and Paper Association, Washington, DC, 1995.
(AFPA, 1991), National Design Specification for Wood Construction, American Forest and
Paper Association, Washington, DC, 1991.
(AGA, 2012), Hot Dip Galvanizing For Corrosion ProtectionA Specifiers Guide, American
Galvanizers Association, Aurora, CO, 2006.
(AISC, 2005a), Specification for Structural Steel Buildings, ANSI/AISC 360-05, American
Institute of Steel Construction, Chicago, IL, 2005.
(AISC, 2005b), Seismic Provisions for Structural Steel Buildings, ANSI/AISC 341-05, American
Institute of Steel Construction, Chicago, IL, 2005.
(AISI, 2015a), North American Standard for Cold-Formed Steel Structural Framing, AISI S240-15,
American Iron and Steel Institute, Washington, DC, 2015.
(AISI, 2015b), North American Standard for Seismic Design of Cold-Formed Steel Structural
Systems, AISI S400-15, American Iron and Steel Institute, Washington, DC, 2015.
(AISI, 2015c), Code of Standard Practice for Cold-Formed Steel Structural Framing, AISI S202-15,
American Iron and Steel Institute, Washington, DC, 2015.
(AISI, 2015d), North American Standard for Cold-Formed Steel FramingNonstructural
Members, AISI S220-15, American Iron and Steel Institute, Washington, DC, 2015.
(AISI, 2013), Standard Test Methods for Determining the Tensile and Shear Strength of Screws,
AISI S904-13, American Iron and Steel Institute, Washington, DC, 2013.
(AISI, 2012a), North American Specification for the Design of Cold-Formed Steel Structural
Members, AISI S100-12, American Iron and Steel Institute, Washington, DC, 2012.
(AISI, 2012b), North American Standard for Cold-Formed Steel FramingGeneral Provisions,
AISI S200-12, American Iron and Steel Institute, Washington, DC, 2012.
(AISI, 2012c), North American Standard for Cold-Formed Steel FramingProduct Data, AISI
S201-12, American Iron and Steel Institute, Washington, DC, 2012.
(AISI, 2012d), North American Standard for Cold-Formed Steel FramingFloor and Roof System
Design, AISI S210-07 (2012), American Iron and Steel Institute, Washington, D.C., 2012.
(AISI, 2012e), North American Standard for Cold-Formed Steel FramingWall Stud Design, AISI
S211-07 (2012), American Iron and Steel Institute, Washington, D.C., 2012.
(AISI, 2012f), North American Standard for Cold-Formed Steel FramingHeader Design, AISI
S212-07 (2012), American Iron and Steel Institute, Washington, D.C., 2012.
(AISI, 2012g), North American Standard for Cold-Formed Steel FramingLateral Design, AISI
S213-07 w/S1-09 (2012), American Iron and Steel Institute, Washington, D.C., 2012.
This document is copyrighted by AISI. Any redistribution is prohibited.

AISI S240-15-C

(AISI, 2012h), Standard for Cold-Formed Steel FramingPrescriptive Method for One- and TwoFamily Dwellings, AISI S230-07 w/S2-08 (2012), American Iron and Steel Institute,
Washington, D.C., 2012.
(AISI, 2012i), North American Standard for Cold-Formed Steel FramingTruss Design, AISI
S214-12, American Iron and Steel Institute, Washington, DC, 2012.
(AISI, 2007a), North American Specification for the Design of Cold-Formed Steel Structural
Members, AISI S100-07, American Iron and Steel Institute, Washington, DC, 2007.
(AISI, 2007b), Design Guide for Cold-Formed Steel Framing, D110-07, American Iron and Steel
Institute, Washington, DC, 2007.
(AISI, 1997), Cold-Formed Steel Back-To-Back Header Assembly Tests, Publication RG-9719,
American Iron and Steel Institute, Washington, DC, 1997.
(AISI, 2002), Cold-Formed Steel Framing Design Guide, American Iron and Steel Institute,
Washington, D.C., 2002.
(AFPA, 2008), ASD/LRFD Special Design Provisions for Wind and Seismic, American Forest &
Paper Association, Washington, DC, 2008.
(APA, 2005), Fastener Loads for PlywoodScrews, Technical Note E380D, APA-The
Engineered Wood Association, Tacoma, WA, 2005.
(APA, 2004), Panel Design Specification, APAThe Engineered Wood Association, Tacoma,
WA, 2004.
(APA, 2001), Diaphragms and Shear Walls: Design/Construction Guide, APA-The Engineered
Wood Association, Tacoma, WA, 2001.
(APA, 2000), Plywood Diaphragms, Report 138, APA-The Engineered Wood Association,
Tacoma, WA, 2000.
(APA, 1993), Wood Structural Panel Shear Walls, Report 154, APA-The Engineered Wood
Association, Tacoma, WA, 1993.
(ASCE, 2013), Minimum Design Loads for Buildings and Other Structures, ASCE 7-10 Including
Supplement No. 1, American Society of Civil Engineers, Reston, VA, 2013.
(ASCE, 2006), Minimum Design Loads for Buildings and Other Structures, ASCE 7-05 Including
Supplement No. 1, American Society of Civil Engineers, Reston, VA, 2006.
(ASHRAE, 2009), ASHRAE Handbook Fundamentals, American Society of Heating
Refrigerating and Air-Conditioning Engineers, Atlanta, GA, 2009.
(ASTM, 2015), Standard Specification for Steel Sheet, Carbon, Metallic- and Non-mMetallicCoated for Cold-Formed Framing Members, ASTM A1003/1003M-15, ASTM International,
West Conshohocken, PA, 2015.
(ASTM, 2014a), Standard Specification for Steel Self-Piercing Tapping Screws for the Application
of Gypsum Panel Products or Metal Plaster Bases to Wood Studs or Steel Studs, ASTM C100214, ASTM International, West Conshohocken, PA, 2014.
(ASTM, 2014b), Standard Practice for Establishing Conformance to the Minimum Expected
Corrosion Characteristics of Metallic, Painted-Metallic, and Nonmetallic-Coated Steel Sheet
Intended for Use as Cold-Formed Framing Members, ASTM A1004/A1004M-99(2014),
ASTM International, West Conshohocken, PA, 2014.
(ASTM, 2013), Standard Specification for Steel Tapping Screws for Cold-Formed Steel Framing
Connections, ASTM C1513-13, ASTM International, West Conshohocken, PA, 2013.

This document is copyrighted by AISI. Any redistribution is prohibited.

Commentary on the North American Standard For Cold-Formed Steel Structural Framing, 2015 Edition

(ASTM, 2011a), Standard Specification for Steel Drill Screws for the Application of Gypsum Panel
Products or Metal Plaster Bases to Steel Studs From 0.033 in. (0.84 mm) to 0.112 in. (2.84 mm)
in Thickness, ASTM C954-11, ASTM International, West Conshohocken, PA, 2011.
(ASTM, 2011b), Standard Specification for Nonstructural Steel Framing Members, ASTM C64511, ASTM International, West Conshohocken, PA, 2011.
(ASTM, 2011c), Standard Specification for Load-Bearing (Transverse and Axial) Steel Studs,
Runners (Tracks), and Bracing or Bridging for Screw Application of Gypsum Board and Metal
Plaster Bases, ASTM C955-11, ASTM International, West Conshohocken, PA, 2011.
(ASTM, 2011d), Standard Specification for Installation of Load Bearing (Transverse and Axial)
Steel Studs and Related Accessories, ASTM C1007-11a, ASTM International, West
Conshohocken, PA, 2011.
(ASTM, 2011e), Standard Method for Static Load Testing of Framed Floor or Roof Diaphragm
Constructions for Buildings, ASTM E455-11, ASTM International, West Conshohocken,
PA, 2011.
Bolte, W. G. (2003), Behavior of Cold-Formed Steel Stud-to-Track Connections, Thesis
presented to the faculty of the University of Missouri-Rolla in partial fulfillment for the
degree Master of Science, 2003.
(CFSEI, 2012), Powder Actuated Fasteners in Cold-Formed Steel Construction, Tech Note F30112, Cold-Formed Steel Engineers Institute, Washington, DC, 2012.
(CFSEI, 2011), Screw Fastener Selection for Cold-Formed Steel Frame Construction, Tech Note
F102-11, Cold-Formed Steel Engineers Institute, Washington, DC, 2011.
(CFSEI, 2010a), Top Track Load Distribution Members, Tech Note W104-10, Cold-Formed Steel
Engineers Institute, Washington, DC, 2010.
(CFSEI, 2010b), Welding Cold-Formed Steel, Tech Note 560-b1, Cold-Formed Steel Engineers
Institute, Washington, DC, 2010.
(CFSEI, 2009), Pneumatically Driven Pins For Wood Based Panel Attachment, Tech Note F30009, Cold-Formed Steel Engineers Institute, Washington, DC, 2009.
(CFSEI, 2007a), Durability of Cold-Formed Steel Framing Members, Tech Note D001-07, ColdFormed Steel Engineers Institute, Washington, DC, 2007.
(CFSEI, 2007b), Corrosion Protection for Cold-Formed Steel Framing in Coastal Areas, Tech Note
D200-07, Cold-Formed Steel Engineers Institute, Washington, DC, 2007.
Cobeen, K. (2010), Cold-Formed Steel Framing Seismic Design Optimization Phase 1a:
Seismic Equivalency Parameter Evaluation, American Iron and Steel Institute Research
Report RP10-4, Washington, DC, 2010.
(CSA, 2014), Connectors for Masonry, CAN/CSA-A370-14, Canadian Standards Association,
Mississauga, Ontario, Canada, 2014.
(CSA, 2012), North American Specification for the Design of Cold-Formed Steel Structural
Members, CAN/CSA S136-12, Canadian Standards Association, Mississauga, Ontario,
Canada, 2012.
(CSA, 2004), North American Specification for the Design of Cold-Formed Steel Structural
Members, 2001 Edition with 2004 Supplement, CAN/CSA-S136-01 with CAN/CSA-S136S104, Canadian Standards Association, Mississauga, Ontario, Canada, 2004.
(CSA, 2003a), CSA-O151-78 (R2003), Canadian Softwood Plywood, Canadian Standards
Association, Mississauga, Ontario, Canada, 2003.

This document is copyrighted by AISI. Any redistribution is prohibited.

AISI S240-15-C

(CSA, 2003b), CSA-O121-78 (R2003), Douglas Fir Plywood, Canadian Standards Association,
Mississauga, Ontario, Canada, 2003.
(CSA, 2003c), CAN/CSA-O325.0-92 (R2003), Construction Sheathing, Canadian Standards
Association, Mississauga, Ontario, Canada, 2003.
(CSA, 2001), CAN/CSA-O86, Engineering Design in Wood, Canadian Standards Association,
Mississauga, Ontario, Canada, 2001.
(CSA,1994), CAN/CSA S16-94, Limit States Design of Steel Structures, Canadian Standards
Association, Mississauga, Ontario, Canada, 1994.
Daudet, L. R. (2001), Recent Research on Stud/Track Connections, October 2001
Newsletter, Light Gauge Steel Engineers Association, Washington, DC, 2001.
Dawe, J.L. (2005), Experimental Evaluation of the Strength and Behaviour of 16- and 18Gauge Cold Formed Steel Top Track Systems - 92 mm and 152 mm, 16 and 24 Spans
(W & W/O 2X4 and 2X6 Wood Top Plates, University of New Brunswick Structural
Engineering Laboratory, Saint John, New Brunswick, Canada, 2005.
Dolan, J.D. (1999), Monotonic and Cyclic Tests of Long Steel-Frame Shear Walls With
Openings, Report No. TE-1999-001, Virginia Polytechnic Institute and State University,
Blacksburg, VA, 1999.
Dolan, J.D., and Easterling, W.S. (2000a), Monotonic and Cyclic Tests of Light-Frame Shear
Walls With Various Aspect Ratios and Tie-Down Restraints, Report No. TE-2000-001,
Virginia Polytechnic Institute and State University, Blacksburg, VA, 2000.
Dolan, J.D., and Easterling, W.S. (2000b), Effect of Anchorage and Sheathing
Configuration on the Cyclic Response of Long Steel-Frame Shear Walls, Report No. TE2000-002, Virginia Polytechnic Institute and State University, Blacksburg, VA, 2000.
Elhajj, N.R., and LaBoube, R. A. (2000), L-Header Testing, Evaluation and Design
Methodology, Proceedings of the 15th International Specialty Conference on Cold-Formed Steel
Structures, Department of Civil Engineering, University of Missouri-Rolla, Rolla, MO,
2000.
Findlay, P.F. (2005), Serviceability Issues Pertaining to Load Bearing and Non-Load
Bearing Steel Framed Walls, Thesis presented to the faculty of the University of
Missouri-Rolla in partial fulfillment of the degree, Master of Science, Rolla, MO, 2005.
Fisher, J.M. and West, M.A. (1990), Serviceability Design Considerations for Low-Rise Buildings,
Steel Design Guide Series No. 3, American Institute of Steel Construction, Chicago IL,
1990.
Fox, S.R. (2006), The Strength of CFS Floor Assemblies with Clip Angle Bearing
Stiffeners, Proceedings of the 18th International Specialty Conference on Cold-Formed Steel
Structures, Department of Civil Engineering, University of Missouri-Rolla, Rolla, MO,
2006.
Fox, S.R. (2003), The Strength of Stiffened CFS Floor Joist Assemblies with Offset
Loading, American Iron and Steel Institute, Washington, DC, 2003.
Fox, S. R., and Schuster, R. (2000), Lateral Strength of Wind Load Bearing Wall Stud-toTrack Connections, Proceedings of the Fifteenth International Specialty Conference on ColdFormed Steel Structures, University of Missouri-Rolla, Rolla, MO, 2000.
(GA, 2001), Gypsum Board Typical Mechanical and Physical Properties, GA-235-01,
Gypsum Association, MD, 2001.

This document is copyrighted by AISI. Any redistribution is prohibited.

Commentary on the North American Standard For Cold-Formed Steel Structural Framing, 2015 Edition

Gerloff, J. R., Huttelmaier, P., and Ford, P. W. (2004), Cold-Formed Steel Slip-Track
Connection, Proceedings of the Seventeenth International Specialty Conference on ColdFormed Steel Structures, University of Missouri-Rolla, Rolla, MO, 2004.
(ICBO, 1997), Uniform Building Code, International Conference of Building Officials,
Whittier, CA, 1997.
(ICBO, 1994), Uniform Building Code, International Conference of Building Officials,
Whittier, CA, 1994.
(ICC, 2015), International Building Code, International Code Council, Washington, DC, 2015.
(ICC, 2012), International Building Code, International Code Council, Washington, DC, 2012.
(ICC, 2003), International Building Code, International Code Council, Falls Church, VA, 2003.
LaBoube, R. A. (2004), Strength of Single L-Headers, Summary Report, Wei-Wen Yu
Center for Cold-Formed Steel Structures, Department of Civil Engineering, University of
Missouri-Rolla, Rolla, MO, 2004.
Lee, Y.K. (1995), Analysis of Gypsum-Sheathed Cold-Formed Steel Wall Stud Panels,
Engineering Report in partial fulfillment of the degree Master of Science, Department of
Civil Engineering, Oregon State University, Corvallis, OR, 1995.
Lewis, A.V (2008), Strength of Cold-Formed Steel Jamb Stud to Track Connections, MASc Thesis,
Department of Civil Engineering, University of Waterloo, Waterloo, Ontario, Canada,
2008.
(LGSEA, 1998), Lateral Load Resisting Elements: Diaphragm Design Values, Tech Note 558b-1,
Light Gauge Steel Engineers Association, Washington, DC, 1998.
Miller, T. H. (1989), Studies on the Behavior of Cold-Formed Steel Wall Stud Assemblies,
Ph.D. dissertation, Department of Civil Engineering, Cornell University, Ithaca, NY,
1989.
(NAHB, 2005), Cold-Formed Steel Walls with Fiberboard Sheathing Shear Wall Testing,
NAHB Research Center, Upper Marlboro, MD, 2005.
(NAHB, 2006), Cyclic Testing of Fiberboard Shear Walls With Varying Aspect Ratios,
NAHB Research Center, Upper Marlboro, MD, 2005.
(NAHB-RC, 2003), Cold-Formed Steel Top Load Bearing Tracks, NAHB Research Center,
Upper Marlboro, MD, 2003.
(NAHB-RC, 2003a), Testing of Steel Single L-Headers, NAHB Research Center, Upper
Marlboro, MD, 2003.
(NBCC, 2005), National Building Code of Canada, NBCC 2005, National Research Council of
Canada, Ottawa, Ontario, Canada, 2005.
(NEHRP, 2000), NEHRP Recommended Provisions for Seismic Regulations for New Buildings and
Other Structures, Federal Emergency Management Agency (FEMA 368/March 2001),
Washington, DC, 2000.
(NFPA, 2011), National Electrical Code (NFPA 70), National Fire Protection Association,
Quincy, MA, 2011.
(NFPA, 2015), NFPA 5000, Building Construction and Safety Code, National Fire Protection
Association, Quincy, MA, 2015.
(NFPA, 2003), NFPA 5000, Building Construction and Safety Code, National Fire Protection
Association, Quincy, MA, 2003.

This document is copyrighted by AISI. Any redistribution is prohibited.

AISI S240-15-C

(NRCC, 2010), Users Guide NBC 2010 Structural Commentaries (Part 4, of Division B),
National Research Council of Canada, Ottawa, Ontario, Canada, 2010.
(NRCC, 2005), National Building Code of Canada, 2005 Edition, National Research Council of
Canada, Ottawa, Ontario, Canada, 2005.
Park, R., (1989), Evaluation of Ductility of Structures and Structural Assemblages from
Laboratory Testing, Bulletin of the New Zealand National Society for Earthquake Engineering
22(3), 1989.
(PFS, 1996), Racking Load Tests for American Fiberboard Association, PFS Corporation,
Madison, WI, 1996.
Ravindra, M.K., and T.V. Galambos (1978), Load and Resistance Factor Design for Steel,
Journal of the Structural Division, American Society of Civil Engineers, 104(ST9), 13371353, 1978.
Rokas, D., (2006), Testing of Light Gauge Steel Frame/9.5mm CSP Panel Shear Walls,
Masters Project, Department of Civil Engineering and Applied Mechanics, McGill
University, Montreal, Quebec, Canada, 2006.
Salmon, C.G., and J.E. Johnson (1996), Steel Structures Design and Behavior, 4th Edition,
Harper Collins, New York, NY, 1996.
(SBCCI, 1999), Standard Building Code, Southern Building Code Congress International,
Birmingham, AL, 1999.
Schafer, B.W. (2008), Design Aids and Examples for Distortional Buckling, Cold-Formed
Steel Engineers Institute, Technical Note G100-08, Washington, DC, 2008.
Schafer, B.W., R.H. Sangree, Y. Guan(2008), Floor System Design for Distortional Buckling
Including Sheathing Restraint, Proceedings of the Nineteenth International Specialty
Conference on Cold-Formed Steel Structures, St Louis, MO, October 14-15, 2008.
Schafer, B.W., R.H. Sangree, Y. Guan (2007), Experiments on Rotational Restraint of
Sheathing, Final Report, American Iron and Steel Institute, , July 2007.
(SEAOC, 1999), Recommended Lateral Force Requirements and Commentary, Structural
Engineers Association of California, Sacramento, CA, 1999.
Serrette, R.L. (1995a), Shear Wall Design and Testing, Newsletter for the Light Gauge
Steel Engineers Association, Light Gauge Steel Engineers Association, Nashville, TN,
1995.
Serrette, R.L., et al. (1995b), Light Gauge Steel Shear Walls Recent Test Results,
Proceedings of the Third International Conference on Steel and Aluminum Structures, MAS
Printing Co., Istanbul, Turkey, 1995.
Serrette, R.L. (1996), Shear Wall Values for Light Weight Steel Framing, Final Report,
Santa Clara University, Santa Clara, CA, 1996.
Serrette, R.L. (1997), Additional Shear Wall Values for Light Weight Steel Framing, Final
Report, Santa Clara University, Santa Clara, CA, 1997.
Serrette, R.L. (2002), Performance of Cold-Formed Steel-Framed Shear Walls: Alternative
Configurations, Final Report: LGSRG-06-02, Santa Clara University, Santa Clara, CA,
2002.
Serrette, R., et al. (2006), Cold-Formed Steel Frame Shear Walls Utilizing Structural
Adhesives, Journal of Structural Engineering, American Society of Civil Engineers,
Reston, VA, 2006.

This document is copyrighted by AISI. Any redistribution is prohibited.

Commentary on the North American Standard For Cold-Formed Steel Structural Framing, 2015 Edition

Serrette, R.L. and K. Chau(2003), Estimating the Response of Cold-Formed Steel-Frame

Shear Walls, Santa Clara University, Santa Clara, CA, 2003.
(SFA, 2008), Thermal Design and Code Compliance for Cold-Formed Steel Walls, Steel Framing
Alliance, Washington, DC, 2008.
Sokol, M.A., R.A LaBoube and W.W. Yu (1999), Determination of the Tensile and Shear
Strengths of Screws and the Effect of Screw Patterns on Cold-Formed Steel
Connections, Civil Engineering Study 98-3, Cold-Formed Steel Series, Center for ColdFormed Steel Structures, University of Missouri-Rolla, Rolla, MO., 1999.
Stephens, S.F., and R.A. LaBoube (2000), Structural Behavior of Cold-Formed Steel Header
Beams for Residential Construction, Proceedings of the Fifteenth International Specialty
Conference on Cold-Formed Steel Structures, Department of Civil Engineering University of
Missouri-Rolla, Rolla, MO, 2000.
Stephens, S.F. (2001), Behavior of Cold-Formed Steel Header Beams, Ph.D. dissertation,
University of Missouri-Rolla, Rolla, MO, 2001.
Stone, T.A. and R.A. LaBoube (2005), Behavior of Built-Up Cold-Formed Steel I-Sections,
Thin-Walled Structure, Elsevier Ltd, 43, 2005.
Tarpy, T.S. (1980), Shear Resistance of Steel-Stud Walls Panels, Proceedings of the Fifth
International Specialty Conference on Cold-Formed Steel Structures, University of MissouriRolla, Rolla, MO, 1980.
Tarpy, T.S., and J.D. Girard (1982), Shear Resistance of Steel-Stud Wall Panels, Proceedings
of the Sixth International Specialty Conference on Cold-Formed Steel Structures, University of
Missouri-Rolla, Rolla, MO, 1982.
Tarpy, T.S., and S.F. Hauenstein (1978), Effect of Construction Details on Shear Resistance
of Steel-Stud Wall Panels, Project No. 1201-412, Department of Civil Engineering,
Vanderbilt University, Nashville, TN, 1978.
Tarpy, T.S., and A.R. McBrearty (1978), Shear Resistance of Steel-Stud Wall Panels with
Large Aspect Ratios, Report No. CE-USS-2, Department of Civil Engineering,
Vanderbilt University, Nashville, TN, 1978.
Tarpy, T.S., and C.S. McCreless (1976), Shear Resistance Tests on Steel-Stud Wall Panels,
Department of Civil Engineering, Vanderbilt University, Nashville, TN, 1976.
Winter, G. (1960), Lateral Bracing of Columns and Beams, Transactions No. 125, American
Society of Civil Engineers, Reston, VA, 1960.
Wood, L. (1960), Relation of Strength of Wood to Duration of Load, U.S. Department of
Agriculture, Forest Products Laboratory, Report No. 1916, Madison, WI, 1960.
Yu, C (2007), Steel Sheet Sheathing Options for Cold-Formed Steel Framed Shear Wall
Assemblies Providing Shear Resistance, Report No. UNT-G76234, Department of
Engineering Technology, University of North Texas, Denton, TX, 2007.
Yu, C., Yujie Chen (2009), Steel Sheet Sheathing Options for Cold-Formed Steel Framed
Shear Wall Assemblies Providing Shear Resistance Phase 2, Report No. UNT-G70752,
Department of Engineering Technology, University of North Texas, Denton, TX, 2009.
Yu, W.W. and R.A. LaBoube (2010), Cold-Formed Steel Design, 4th Edition, John Wiley &
Sons, New York, NY, 2010.
Advisory Note: The Light Gauge Steel Engineers Association (LGSEA) in 2006 changed its name to the
Cold-Formed Steel Engineers Association (CFSEI). CFSEI is located at AISI headquarters in Washington,
DC.

This document is copyrighted by AISI. Any redistribution is prohibited.

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