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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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BEHAVIOUR IN TENSION
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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BEHAVIOUR IN TENSION
Plates with Holes
An = [ b n d + (p2 / 4 g)]t
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BEHAVIOUR IN TENSION
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
Revised IS 800:2007 CODAL PROVISIONS
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Fig. 6.2 Angles with end connections
bs=w
ww
w1
bs=w+w1
Revised IS 800:2007 CODAL PROVISIONS
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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
Revised IS 800:2007 CODAL PROVISIONS
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DESIGN OF TENSION MEMBERS
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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DESIGN OF TENSION MEMBERS
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/