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TENSION MEMBERS

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Dr S R Satish Kumar IIT Madras 2

DESIGN OF TENSION MEMBERS

Introduction

Behaviour of Tension Members

Plates Under Tension

Threaded Rods

Angles Under Tension

Code Provisions

Summary

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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

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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

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INTRODUCTION

Built up sections

Angle Double AngleChannel

Rod Cable

Cross Sections Used for Tension Members

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BEHAVIOUR IN TENSION

Plates with a Hole

(a) Elastic (b) Elasto-Plastic (c) Ultimate

uy

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Plates with Holes (Cl 6.3)

(b)(a)

(c)

P = pitch

g = gauge

1

1 4p

g2

3

bd

Case a: Net Area: = t (b - 2*d)

Case b: Net Area: = t (b

d)

Case c: t (b - 2*d)

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Plates with Holes

An = [ b n d + (p2 / 4 g)]t

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ANGLES Eccentrically Loaded Through Gussets

Gusset plate

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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

6.3.2 Threaded Rods

6.3.3 Single Angles

6.3.4 Other Sections

6.4 Design Strength due to Block Shear

6.4.1 Plates

6.4.2 Angles

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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= fyAg / 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 fuAn/ m1 m1 = 1.25

An = Contt

g

pndb

i i

ih

4

2

Revised IS 800:2007 CODAL PROVISIONS

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6.3.2 Threaded Rods

The design strength of threaded rods in tension, Tdn,

Tdn=0.9 fuAn/m1

Ultimateelastic elastic -Plastic

droot

dgross

f

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6.3.3SingleAnglesThe design strength, Tdn, as governed

by tearing

Tdn =0.9fuAnc / m1 + Ago fy/ m0

=1.4 0.076(w/t)(fu/fy)(bs/L ) [1.4-0.52(bs/L)]

Alternatively, the tearing strength of net section may be

taken as

Tdn = An fu / m


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Fig. 6.2 Angles with end connections

bs=w

ww

w1

bs=w+w1


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6.4 Design Strength due to Block Shear

6.4.1 PlatesThe block shear strength, Tdb, of connection shall be taken as the

smaller of

Tdb= ( Avg fy/( 3 m0) +fu Atn / m1 )

or

Tdb= ( fuAvn/( 3 m1) + fyAtg/ m0)

Fig 6.2 Block Shear Failure of Plates

12

43

1 2

3

Fig 6.3 Block Shear Failure of Angles

4


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Stiffness RequirementsDesigned for compression under

stress reversal /r < 250

Not designed for compression under

stress reversal /r < 350

Members under tension only /r < 400

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Summary

Efficient load carrying members

Efficiency may reduce due to

bolt holes

shear lag

block shear

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www.steel-insdag.org

Dr S R Satish KumarAsso. Professor & Head,

Structural Engineering Laboratory,

Dept. of Civil Engineering,IIT Madras, Chennai 600 [email protected]
http://www.steel-insdag.org/mailto:[email protected]:[email protected]://www.steel-insdag.org/http://www.steel-insdag.org/http://www.steel-insdag.org/

IS800-6Tens_140

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