HSS Design with the Latest Codes
and Material Specifications
Kimberley Olson, PE
Technical Consultant to the Steel
Tube Institute
Topics
Uses
Materials
Availability
Connections
History
Structural members have been around for centuries.
They’ve been used as flexural load carrying
members…as columns and beams in huts and
housing…and for scaffolding.
Galileo studied structural members in the 15th
century. He called them “hollow solids” and
analyzed specific examples from nature — the stems
of flowers…the bones of animals…bamboo…
structural members which are lightweight and
flexible, yet strong.
Compression
No weak axis ‐ great for columns
Torsion
Torsional constant of an HSS is ≈200
times that of an open section
HSS Wide Flange
Torsion
Torsion
Example:
Beam length 30’
torsional load 1.2 ft‐k/ft
W18x35 ϴ = 2.41 rad
HSS12x6x5/16 ϴ = 0.0063 rad
Blast Loading
HSS are good blast resistant members
• direction of loading
• higher torsional rigidity
• composite HSS members
Manufacturing Process
Two processes:
• Electric Resistance Welding (ERW)
• Weld ‐ Round, Form ‐ Square
Process (continuous forming)
• Form ‐ Square, Weld ‐ Square
Process (direct forming)
• Submerged Arc Welding (SAW)
Manufacturing Process
All starts when steel coils are split
into proper widths
Weld ‐ Round, Form ‐ Square
Form ‐ Square, Weld ‐ Square
Submerged Arc Welding
HSS Materials
A500
A1085
A1065
A847
A53
A252
ASTM A500
…has been around since the late 70’s
ASTM A500
Excerpt from ASTM A500‐13
The 0.93 Reduction
Design wall Supporting
Spec Designation Comments
thickness Manual
1989 ASD (1) tnom 9th Ed. ASD TS
1986 LRFD tnom 1st Ed. LRFD TS
1993 LRFD (2) tnom 2nd Ed. LRFD TS
1997 HSS Supplement to the
0.93 x tnom (3) NA (4) HSS
(LRFD) 1993 LRFD Spec.
1999 LRFD (2) 0.93 x tnom (3) 3rd Ed. LRFD HSS
2000 HSS Supplement to the
0.93 x tnom (3) 3rd Ed. LRFD HSS
(LRFD) 1999 LRFD Spec.
2005 ERW: 0.93 x tnom
13th Ed. HSS
(AISC 360-05) SAW: tnom
2010 ERW: 0.93 x tnom
14th Ed. HSS
(AISC 360-10) SAW: tnom
2016 A500: 0.93 x tnom * also includes
15th Ed. HSS
(AISC 360-16) A1085*: tnom A1065
Notes:
(1) Includes previous ASD specifications and Manuals. HSS was not specifically covered in all of these specifications or manuals
(2) The reduction is included by using the appropriate separate HSS Specification
(3) Applies when the actual thickness of the wall is not known
(4) This specification never appeared in the Manual of Steel Construction but it did appear in the HSS Connections Manual.
ASTM A1085
Wall Thickness
Yield Strength tolerance & Mass Corner Radius
tolerance
hold on, i have to
± 10%
look it up…
A500 no mass < 3t
ranges from 33‐
tolerance
50 ksi
50 ksi min, ‐5%, +10% t≤0.4” 1.6t ‐ 3t
A1085
70 ksi max ‐3.5%, +10% t>0.4” 1.8t ‐ 3t
The 0.93 Reduction
ASTM A1085
• 0.93 factor not required!!
• Not in AISC 360 yet but has been
published in Modern Steel
• AISC 360‐16 draft includes A1085
and does not require thickness
reduction
Strength Comparison
Compressive strength: HSS6x6x3/8, kL = 14’
A500 GrB A1085
0.93 x tnom tnom
12%
Fy = 46 ksi increase Fy = 50 ksi
ɸPn = 153k ɸPn = 172k
ASTM A1085
Ry values will go down
Ry = actual yield
spec’d min yield
ASTM A1085
Steels for use in primary bridge members are required to
have sufficient fracture toughness to reduce the probability
of brittle failure in the presence of a fatigue crack or other
notch‐like defect.
CVN test requirement
• Ability of a material to resist fracture under impact
loading
• Measures absorbed energy during fracture
• Cut V in steel and hit with a pendulum, measure how far
the pendulum swings up
• Amount of energy absorbed will increase as temperature
increases
ASTM A1085
AASHTO divides US into three temperature
zones for specifying fracture toughness.
Delineated by lowest anticipated service
temperature
A1065
SAW manufacturing process
only rectangular / square
sections
tapered sections
larger sections (perimeter
greater than 64” and up to 1”
thick)
no reduction in design
thickness
A500 Gr B vs Gr C Smackdown
DUAL CERT!!!
Always specify Grade C!
The Seam Weld
Per A500, “The longitudinal butt joint of
welded tubing shall be welded across its
thickness in such a manner that the structural
design strength of the tubing section is
assured”
A500‐13 adds that the
weld seam shall not be
placed within the radius
ASTM A53
A true pipe specification, intended for
mechanical and pressure applications
(steam, water, air, gas).
Not recommended by STI.
Availability
Connections
Program WF bm to HSS Col HSS Col HSS vert HSS to Mitered Integration
HSS col splices base plate bracing HSS Knee / End
(truss) pl
Enercalc X None
DESCON X X None
Fastrak X Fastrak
Connection
LIMCON X X X X X None
RAM X X X X RSS, RE,
Connection STAAD
RISA X X RISAFloor &
Connection RISA-3D
SDS/2 X X X X REVIT 2014
Connect add-in
STI’s HSS None
checks HSS
Connex
support only
Online
TEDDS X None STI
development
Connections ‐ TEDDS
Connections ‐ TEDDS
Connections ‐ Excel
Single Plate Shear Connection of WF Beam to HSS
Column
Moment Connection of WF Beam to HSS Column
• Continuous Beam over Column
• Through Plate
• Directly Welded
Truss Connection
• K Connection
• T/Y Connection
Connections ‐ Excel
Connections ‐ HSS Connex Online
Proprietary Connections
Sideplate ConXtech
Proprietary Connections
Hollo Bolt* by
Cast Connex
Lindapter, Blind Bolt,
Box Bolt by LNA*
Resources
• AISC Manual & Design Guide 24
• CIDECT Design Guides
• Hollow Structural Section Connection and
Trusses by J.A. Packer & J.E. Henderson
• STI’s Contact page
• Coming Q1/2015 STI Product Manual
Thank you!!
Kim Olson, PE
303.720.4076
kim@forseconsulting.com
