1. TENSION MEMBERS

2. DESIGN OF TENSION MEMBERS
Teaching Resources for Steel Structures
DESIGN OF TENSION MEMBERS
Introduction
Behaviour of Tension Members
Plates Under Tension
Threaded Rods
Angles Under Tension
Code Provisions
Summary
© Dr S R Satish Kumar IIT Madras
© IIT Madras, SERC Madras, Anna Univ., INSDAG Calcutta

3. Tension Members in Buildings
suspenders
(b) Suspended Building
tie
(a) Roof Truss
rafter
(c) Roof Purlin System
purlin
Sag rod
Top chord
(d) Braced frame
© Dr S R Satish Kumar IIT Madras

4. Uniform stress over the cross section Very Efficient Member
INTRODUCTION
Characteristics
Members Experience
Axial force
Stretching
Uniform stress over the cross section
Very Efficient Member
Strength governed by the material strength
Bolt holes affect the strength
© Dr S R Satish Kumar IIT Madras

5. Cross Sections Used for Tension Members
INTRODUCTION
Cross Sections Used for Tension Members
Channel
Angle
Double Angle
Rod
Cable
Built up sections
© Dr S R Satish Kumar IIT Madras

6. BEHAVIOUR IN TENSION Material Properties T fy c  High Strength Steel
Mild Steel
High Strength Steel T  a b c d e fy
0.2%
Yield Plateau
© Dr S R Satish Kumar IIT Madras

7. BEHAVIOUR IN TENSION Plates with a Hole u y (a) Elastic
(b) Elasto-Plastic
(c) Ultimate u y
© Dr S R Satish Kumar IIT Madras

8. b d BEHAVIOUR IN TENSION Plates with Holes (Cl 6.3) (a) (b)
P = pitch
g = gauge 1 4 p g 2 3 b d
Case a: Net Area: = t (b - 2*d)
Case b: Net Area: = t (b – d)
Case c: t (b - 2*d)<Area< t (b –d)
(a)
(b)
(c)
© Dr S R Satish Kumar IIT Madras

9. An = [ b – n d + (p2 / 4 g)]t BEHAVIOUR IN TENSION Plates with Holes
© Dr S R Satish Kumar IIT Madras

10. BEHAVIOUR IN TENSION ANGLES Eccentrically Loaded Through Gussets
Gusset plate
© Dr S R Satish Kumar IIT Madras

11. SECTION 6 DESIGN OF TENSION MEMBERS
Revised IS 800:2007
SECTION 6 DESIGN OF TENSION MEMBERS
6.1 Tension Members
6.2 Design Strength due to Yielding of Gross Section
6.3 Design Strength due to Rupture of Critical Section
6.3.1 Plates
Threaded Rods
Single Angles
6.3.4 Other Sections
6.4 Design Strength due to Block Shear
Plates
Angles
© Dr S R Satish Kumar IIT Madras

12. Revised IS 800:2007 CODAL PROVISIONS
6.1 Tension Members
The factored design tension T, in the members T < Td
6.2 Design Strength due to Yielding of Gross Section
The design strength of members under axial tension Tdg, Tdg = fy Ag /m0
mo = 1.1
6.3 Design Strength due to Rupture of Critical Section
6.3.1 Plates  The design strength in tension of a plate, Tdn,
Tdn =0.9 fu An / m1 m1 = 1.25
An = Cont…
© Dr S R Satish Kumar IIT Madras

13. Revised IS 800:2007 CODAL PROVISIONS
6.3.2 Threaded Rods 
The design strength of threaded rods in tension, Tdn,
Tdn =0.9 fu An / m1
Ultimate
elastic
elastic -Plastic
droot
dgross
f < fy fy fu
© Dr S R Satish Kumar IIT Madras

14. Revised IS 800:2007 CODAL PROVISIONS
6.3.3 Single Angles  The design strength, Tdn, as governed by tearing
Tdn = 0.9 fu Anc / m1 + Ago fy /m0
 = 1.4 – (w/t) (fu/fy) (bs/L ) [≈ (bs/L)]
Alternatively, the tearing strength of net section may be taken as
Tdn =  An fu /m
© Dr S R Satish Kumar IIT Madras

15. Revised IS 800:2007 CODAL PROVISIONS
bs=w w w1
bs=w+w1
Fig. 6.2 Angles with end connections
© Dr S R Satish Kumar IIT Madras

16. Revised IS 800:2007 CODAL PROVISIONS
6.4 Design Strength due to Block Shear
6.4.1 Plates –The block shear strength, Tdb, of connection shall be taken as the smaller of
Tdb = ( Avg fy /(3 m0) + fu Atn /m1 ) or
Tdb = ( fu Avn /(3 m1) + fy Atg /m0 ) 1 2 3
Fig 6.3 Block Shear Failure of Angles 4
Fig 6.2 Block Shear Failure of Plates 1 2 4 3
© Dr S R Satish Kumar IIT Madras

17. DESIGN OF TENSION MEMBERS
Efficiency
 = Pt /(Ag * fy / M0)
Design Steps
An = Pt / (fu / M1)
Ag = Pt / (fy / M0)
Choose a trial section
Analyse for its strength
© Dr S R Satish Kumar IIT Madras

18. DESIGN OF TENSION MEMBERS
Stiffness Requirements
Designed for compression under
stress reversal /r < 250
Not designed for compression under
stress reversal /r < 350
Members under tension only /r < 400
© Dr S R Satish Kumar IIT Madras

19. DESIGN OF TENSION MEMBERS
Summary
Efficient load carrying members
Efficiency may reduce due to
bolt holes
shear lag
block shear
Thank You
© Dr S R Satish Kumar IIT Madras

20. Structural Engineering Laboratory, Dept. of Civil Engineering,
Dr S R Satish Kumar
Asso. Professor & Head,
Structural Engineering Laboratory,
Dept. of Civil Engineering,
IIT Madras, Chennai
© Dr S R Satish Kumar IIT Madras