CE 401 STRUCTURAL DESIGN
LECTURE 1: STEEL CONNECTIONS-BOLTED
CONNECTIONS
Yaip K Telue
BEng, BEng(Hons2A), PhD(QUT)
MIE(Aust), MIE(PNG)
Professor and Head Department of Civil Engineering
PNG Unitech
LECTURE PLAN
Lecturer: Professor Dr Yaip K Telue/Tutor: Kingsford Telue
Subject: CE 401 Structural Design Semester/Year: 1/2012
We Topics (Please indicate the Continuous Learning Objectives to be Perform.
ek Depth to be achieved) Assessment achieved alert +
Quiz Assign Tests 1 2 3 4 5 6
1 Bolted Connections: Design requirements, 1 √ √
capacity reduction factors, Minimum Design Test
Forces, Bolt categories, design requirements 1
for Bolt connection for limit state, Bolts in
shear, tension, combined shear and tension,
ply in bearing, Bolt connection
serviceability limit state. minimum Bolt
pitch, Maximum edge distance.
2 √ √
Bolted Connections: Analysis of Bolt
Connection-In plane Bending
3 Bolted Connections: Analysis of Bolt √ √
Connection-Out of plane Bending
4 Welded Connections: Butt, Fillet , plug & √ √ Alert 1
slot welds, Weld Group Analysis, in plane 2
5 Welded Connections: Out of Plane welds √ √
6 Design of Column Base, Wind Loads. √ √
7 Design of Purlins √ √
Mid Semester Break 3 Test
8 Design of Purlins, Introduction to 2 √ √
Earthquake Loads
9 Introduction to Earthquake Loads √ √ Alert 2
10 Tutorial, Major Project-Design of building. √ √ √
11 Design of footings- axially loaded √ √
12 Design of Footings- eccentrically Loaded √ √ Alert 3
13 Revision
Break
Key:
1- Knowledge 2- Comprehension 3- Application 4 – Analysis 5
- Synthesis 6 - Evaluation
LECTURE PLAN
(a) Textbook:
YK Telue (2012, 3rd Edition), Limit State Design of Steel Structures, PNG
University of Technology, Lae PNG.
PNG Standard, PNGS 1003-1982, Steel Structures
PNG Standard, PNGS 1001-1982, General Structural Design and Design Loadings
for Buildings, Part 4 Earthquake Loads
PNG Standard, PNGS 1001-1982, General Structural Design and Design Loadings
for Buildings, Part 3 Wind Loads.
PNG Standard, PNGS 1001-1982, General Structural Design and Design Loadings
for Buildings, Parts 1 and 2 Dead and Live Loads
PNG Standard, PNGS MP1-1982, Design Manual, to Assist in the Application of
the Code of Practice for General Structural Design and Design Loadings for
Buildings.
Australian Institute of Steel Construction, Structural Connections
Australian Standard, AS 4100 1998, Steel Structures Code
Gorenc, B, Tinyou, R and Syam, A. (2005) Steel Designers’ Handbook, 7th
Edition, UNSW Press, Sydney Australia.
Warner, Rangan, Hall and Faulkes (1999 or Latest edition), Concrete Structures,
Addison Wesley Longman Australia Pty Ltd, South Melbourne. ISBN = 0 582
80247 4
(b) References
Australian Institute of Steel Construction, Safe Loads for Structural Steel (third
edition, 1999)
PNG Standard, PNGS 1002-1982, Reinforced Concrete Structures
Australian Standard AS 3600-2001, Concrete Structures
Reinforced Concrete Detailing Handbook, Concrete Institute of Australia
(c) Assessment: 100%
Continuous Assessment: 50%
2 x tests 20%
2 x Assignments 10%
1 x Major Project 20%
Examination (1 x 3 hours): 50%
BOLTED CONNECTIONS
Types of Connections
The need to joined members
1. Can be made of bolts Bolts in Direct Shear
2. welds
N*
5/M24 Bolts
6 2x PFC
0
N*
2x 180 PFC (Placed back 60
100 mm
4 spaces at 50 mm to back)
= 200 mm
4/ M20 Bolts
10 mm thick Plate
Bolted Connections
12/M20 V* = ??
In Plane Bending Bolts/side PL 525 mm
DL =120
DLkN
=120 kN
Bolts in Tension and Shear 45
LL = 160 kN
5@
70 =
350
16 mm Side Plate
45
60 mm 250 mm 250 mm 60 mm
250 UC 89
BOLTED CONNECTIONS
Out of Plane Bending
Bolts in Tension and Shear
1000 mm
A DL=150 kN
LL= 100 kN
L=
30
A
00
BOLTED CONNECTIONS
More Examples of Out of Plane Bending
Bolts in Tension and Shear
500 mm
V* = 150 kN 250 UC 89
70
4@
70
16 mm PLATE (PL)
=
280
70
20 mm PL
BOLTED CONNECTIONS
Design Requirements for Connections
Requirements for design of connections are included in Section 6.5 and 6.8 of these notes for the bolted and
welded connections respectively. Further procedures can be obtained from AS 4100 and other references
published by Australian Steel Institute (refer to references section of these notes).
Capacity Reduction Factors
Following are the appropriate capacity reduction factors in accordance with AS 4100-1998
Bolts (in shear or tension = 0. 8
Plates (ply) in bearing = 0.9
Other connection components (except main member) = 0.7
Butt Welds = 0.9
Fillet Welds = 0.8
BOLTED CONNECTIONS
Minimum Design Force
The following are the minimum forces specified by the code (AS 4100). For moment joints (rigid
construction) minimum moment of 50% of the member design capacity. For Simple Construction – a
minimum shear force of 40 kN.
At ends of tension or compression members – a minimum force of 30% of the member design capacity. For
Splices – minimum of 30% of member design capacity, except by the full effort of a man using a standard
podger spanner. All the force that may be transmitted by bearing in a compression splice provided fasteners
are provided to transmit a minimum of 15% of the member design capacity.
Net Area of Tension Members
The net area of tension members is covered in Section 2.1 of this book.
BOLTED CONNECTIONS
REQUIREMENTS FOR BOLT CONNECTIONS
Bolt Categories
The three common bolting categories or procedures are the snug tightening, fully tension friction mode (TF)
and the fully tension bearing mode (TB). These are denoted as:
/S: ‘Snug-tight’, bolts tightened by a few impacts of an impact wrench or /TB: Fully tensioned bolts used in
‘bearing’ mode and /TF: Fully tensioned bolts used in ‘friction’ mode.
S, TB and TF bolts of the same grade all have the same strength limit state shear, Tension and bearing
capacities. TF bolts should be used where slip under loads must be avoided such as when subject to impact or
vibration. The serviceability limit state must be satisfied in this design mode. However the strength limit
stated must also be satisfied as for TB bolts.
BOLTED CONNECTIONS
Table 6-1 shows the bolting categories and bolt grade, ultimate tensile strength and the methods of tensioning. The
bolt sizes and areas for computing the shear and tensile stresses are given in Table 6-2.
Table Error! No text of specified style in document.-1: BOLTS AND BOLTING CATEGORY
Bolting Bolt Grade Method of Tensioning Ulitimate tensile Strength (fuf) MPa
Category
4.6/S 4.6 Snug tight 400
8.8/S 8.8 Snug tight 830
8.8/TF 8.8 Full tensioning 830
8.8/TB 8.8 Full tensioning 830
Table Error! No text of specified style in document.-2: AREAS OF TENSIONING OF BOLTS
Areas mm2 TF, TB Tensioning. Max length for
Bolt Size Ao Ac As Tension ½ turn ¼ turn
(diameter) Shank Core Tension Nu (kN) (mm) (mm)
M12
M16 201 144 157 90 120 240
M20 314 225 245 145 120 240
M24 452 324 353 205 160 350
M30 706 561 325 160 350
M36 1017 817 475 160 350
BOLTED CONNECTIONS
Design Requirements of Bolt Connection for Strength Limit State
Bolt in Shear
The design shear force of the bolt is denoted as:
Vf.* Vf ........................................................................................................................................Equation
Error! No text of specified style in document.-1
Where = 0.8 and the nominal shear capacity is given by Equation 6-2.
Vf = (0.62 fuf ) kf nA…………………………………………………………......…………….Equation
Error! No text of specified style in document.-2
Where n = number of shear planes
A = area of bolt = Ac or Ao
Ac = core area of bolt, used when threads intersect the shear plane.
Ao = shank area of bolt, used when threads do not intersect the shear plane
kr = joint length factor = 1 for Li < 300
Li > 1 to > Li/5200 ≥0.75
BOLTED CONNECTIONS
Bolt in Tension
The design tension force is given by Equations 6-3 and 6-4 viz:
Ntf.* Ntf………………………………………………………………………….…………….Equation
Error! No text of specified style in document.-1
Nominal tension capacity Ntf = Asfuf………………..…………..………………………………..Equation
Error! No text of specified style in document.-2
As = tensile stress area of bolt
BOLTED CONNECTIONS
Table Error! No text of specified style in document.-1: Capacities of Grade 4.6/S Bolts
fuf = 400 MPa, =0.8
Bolt Size Shear Capacity for Shear Capacity for Axial Tension
threads excluded from threads included in the
shear plane. shear plane.
Vfx (kN) Vfn (kN) Ntf (kN)
M12 22.4 15.1 27.0
M16 39.9 28.6 50.2
M20 62.3 44.6 78.4
M24 89.7 64.3 113
M30 140 103 180
Table Error! No text of specified style in document.-2: Capacities of Grade 8.8/S, 8.8/TB, 8.8/TB Bolts
fuf = 830 MPa, =0.8
Bolt Size Shear Capacity for Shear Capacity for Axial Tension
threads excluded from threads included in the
shear plane. shear plane.
Vfx (kN) Vfn (kN) Ntf (kN)
M16 82.7 59.3 104
M20 129 92.6 163
M24 186 133 234
M30 291 214 373
BOLTED CONNECTIONS
Bolts Subject to Combined Shear and Tension
(Vf.*/Vf)2 + (Ntf.*/Ntf)2 1.0 ……………….……………………………………………Equation
Error! No text of specified style in document.-1
Where = 0.8 and Vf and Ntf as previously defined.
Ply in Bearing
Design bearing force
Vb*. Vb…………………….........……………………………………….…………………….Equation
Error! No text of specified style in document.-2
= 0.9
where Vb is the plate (ply) bearing capacity and shall be the lesser of 3.2 df tp fup or tp fup.
df = thickness of fastener (bolt)
tp = thickness of the plate (ply)
fup = fu for the plate (ply), usually 410 Mpa
ae = edge distance in direction of force (measured from centre of hole) to edge of plate or to edge of next
hole.
BOLTED CONNECTIONS
Both Connection Serviceability Limit State (8.8/TF only)
Shear
Design shear force
Vsf.* Vaf……………….......……………………………………..…………………………….Equation
Error! No text of specified style in document.-1
= 0.7
where Vsf =shear capacity of bolt friction = nei Nti …...……………………………………….Equation
Error! No text of specified style in document.-2
= friction (slip) factor = 0 .35 for clean ‘as-rolled’ surfaces. Test evidence is required for other surface
conditions.
nei = number of friction interfaces
Nti = minimum bolt tension at installation
Combined Shear and Tension
(Vsf*./Vsf) + (Ntf.*/Ntf) 1.0…….………………………………………………………………..Equation
Error! No text of specified style in document.-3
= 0.7
Where Ntf = nominal tension capacity of the bolt
NOTE: The serviceability limit state is checked only when no slip is required. When this is done the
strength limit state must also be checked
BOLTED CONNECTIONS
1.1.1 Design Details for Bolts
Minimum Pitch (p)
p 2.5df
Where p = pitch i.e distance between centres of bolts
df = bolt (fastener) diameter
Maximum Pitch
p the lesser of 14 tp or 200mm, normally
p lesser of 32 tp or 300mm, no design force,
p lesser of (4 tp + 100 mm) or 200 mm, outside line of fasteners in the direction of force.
tp - thickness of thinnest plate connected.
1.1.1.1 Maximum Edge Distance
ed the lesser of 12tp or 150 mm
tp = is the thickness of the thinnest outer connected plate
BOLTED CONNECTIONS-DIRECT SHEAR
1.1 ANALYSIS OF BOLTED CONNECTIONS
The analysis of bolted connections in direct shear, in the plane of bending and out of plane bending are
presented in the follwing sections.
Direct Shear Example
Check that the 5-M20 grade 4.6 bolts can carry the required maximum axial force, N * = 540 kN. (assume no
eccentricity and all bolts carry equal components of N*). The tie consists of 2- 125 x 125 x 8 angle (placed
back to back) (fy = 320 MPa, fu = 440 MPa) and is connected to the 150 x 16 gusset plate by 5-M20 bolts.
(Plate fy = 250 MPa and fu = 410 MPa).
5/M20 Bolts
*
N ≤ Nt = 0.85 kt An fu
or
60
N* ≤ Nt = Ag fy N*=540 kN
kt = 1.0
= 0.9
Plate fy = 250 MPa 2x 125 x125 x 8 Angle
Plate fu = 410 MPa (Placed back to back)
4 spaces at 50 mm
= 200 mm
t.Sp2/4Sg
BOLTED CONNECTIONS
Check 2- 125 x 125 x 8 angle (placed back to back) (f y = 320 MPa, fu = 440 MPa)
Ag = 2 x 1900 mm2 t = 7.8 mm 1
2
N*
An1 = 2 x1900 – (22 x 7.8) x 2 = 3456.4 mm2
60
An2 = [1900 - (2 x 22 x 7.8) + (7.8 x 502/(4x 60)] x 2 2x 125 x125 x 8 Angle
= [1900 - 343.2 + 81 .3] x 2 = 1638.1 x 2 = 3276.4 mm2 (Placed back to back)
Nt = Ag fy = 0.9 x 320 x 1900 x 2x 10-3 = 1094 kN
Nt = 0.85 kt An fu = 0.9 x 0.85 x 1.0 x 3276.4 x 440 x 10-3 = 1103 kN
Nt (angle) = 1094 kN >N* (Connection) = 540 kN OK.
BOLTED CONNECTIONS
Plate
1
Plate fy = 250 MPa 2
5/M20 Bolts
Plate fu = 410 MPa 60
Ag = 150 x 16 = 2400 mm2 N*
An1 = 2 400 – (22 x 16) = 2400 – 352 = 2048 mm2
An2 = [2 400 – (22 x 16 x 2) + (16 x 502/(4x 60)]
= [2400 - 704 + 166.7 = 1862.7 mm2
Nt = Ag fy = 0.9 x 250 x 2400 x 10-3 = 540 kN
Nt = 0.85 kt An fu = 0.9 x 0.85 x 1.0 x 1862.7 x 410 x 10-3 = 584.2 kN
Nt (Plate) = 540 kN >N* (Connection) = 540 kN OK.
5/M20 Bolts
60
N* = 540 kN
2x 125 x125 x 8 Angle
(Placed back to back)
4 spaces at 50 mm
= 200 mm
BOLTED CONNECTIONS
Bolt Capacity
Minimum centre to centre spacing of bolts = 2.5 x df = 2.5 x 20 = 50 mm OK
For 5 M20 Grade 4.6 bolts
N*= 540 kN (This is a tension force as far as the angle and the gusset plate are concerned. However it is a
shear load on the 5 bolts. i.e the total shear force on the 5 bolts)
V*per bolt = 540/(5x2) = 54 kN (note bolts are in double shear) (this is the shear force on one bolts.
From Safe Load Tables
Vfn = 44.6 kN/bolt (threads included in the shear plane) < V* =54 kN NOT OK !
Vfx = 62.3 kN/bolt (threads excluded in the shear plane) > V* =54 kN OK !
Ntf = 78.4 kN (Not required here as bolts are not in tension)
OR calculate Total Vf = 2 x 44.6 x 5 = 446 kN < N * = 540 kN NOT OK! So the connection will fail at
the bolts. (If the threads are included in the shear plane).
BOLTED CONNECTIONS
Check Edge distances ae
ae = 1.5 x df = 1.5 x 20 = 30 mm
Check Bearing and Tearing Stresses with Section 9.3.2.4 (AS 4100)
Plate
V* = 540/5 = 108 kN
Vb = 3.2 x df tp fup = 3.2 x 20 x 16 x 410 x 10-3 = 419.8 kN (Bearing)
Vb = ae tp fup = 30 x 16 x 410 x 10-3 = 196.8 kN (Tearing)
Vb = 0.9 x 196.8 = 177.1 kN > V* = 108 kN OK.
Angle
V* = 540/(5 x 2) = 54 kN
Vb = 3.2 x df tp fup = 3.2 x 20 x 7.8 x 440 x 10-3 = 219.6 kN (Bearing)
Vb = ae tp fup = 30 x 7.8 x 440 x 10-3 = 103.0 kN (Tearing)
Vb = 0.9 x 103 = 92.7 kN > V* = 54 kN OK.
30 mm edge distance is OK.
