Week 2 Challenge

Design of Tension Member

1. Net Area for tension member calculation problem

Calculate the net section area for the tension member as shown in Figure below. The plate size is 260 x 20 thick and Bolt size is 20 mm.

Plate – Drilled Hole

Plate – Zigzag bolting

Angle (200 x 100 x 12 with M20 bolt)

ANS

PLATE - DRILLIED HOLE

NET SECTION AREA FOR THE TENSION MEMBER-

An = ( b-ndh )* t

=where b= with of plate

n= no of bolt at critical secton

dh = diameter of bolt hole

t= thickness of plate

= (260-4*22)*20 = 3440 mm2

plate= zig-zag bolting

Along bolt A-C-D

An = ( b-ndh +`sum`psi2/4gi) *t

=( 260 -3 *22 +2*60*60/4*60) *20

= 4480 MM^2

2. Sag rod design problem

Design a sag rod as shown in Figure below. Purlins are supported at 1/3^rd points by sag rods.

Assume centre to centre distance of Rafter spaced at 8 m , spacing of purlin = 1.2 m, Self weight of roofing (including thermal insulation)= 60 kg/m² , Wind pressure intensity = 150 kg/m²,Slope of rafter = 15 degrees, Live Load =75 kg/m². Assume self weight of purlin as 100 kg/m.

GRAVITY LOAD ON THE PURLIN.

(DEAD LOAD +LIVE LOAD ) ON THE PURLIN - 60 KG/M2*1.2M +75KG/M2*1.2 +100 =262 KG/M = 2.62 KN/M

WIND LOAD ACTING ON THE PURLIN.

= 2.62*SIN15 = 0.678 KN/M

FORCE ON SAG ROD= 0.67*(1/3) *SPACING

=0.67*1/3*8 = 1.79 KN

FACTORED OAD =1.5*1.79 = 2.69 KN

REQUIRED NET AREA.

An = Tdn*ym1/0.9*Fu = 2.69*10^3 *1.25/0.9*410 =9.112 mm2

provide 12 mm sag rod= 3.14/4x 12*12 = 113 mm2

3. Determine section size for given tensile load

Design a single angle member of length 5m to carry axial tensile force of 500 kN. Yield strength fy of the material to be considered is 350 N/mm².

give data

p= 500kn

l =5m

fy = 350 n/mm2

• Calculate required area of cross section from factored load

factoreed load = 1.5*500 = 750kn

required area Ag = Td *ymo/Fy

= 750* 1.1/350 = 2357 mm2

choose the setion from the table whose area graeter than this.

choose section isa 110x110x8 mm

design strength of member due to yieldig = Tdg = Ag x fy / ymo

2502 x 350 /1.1 = 796 kn>750kn ok

design strength of member by tearing of net section =

Tdn = 0.9 x Fu x Anc/ym1

=0.9 * 400 *(110-4-20)*8 /1.125 =220 kn

SLENDERNESS RATIO= kl / r min =5*1000/6 = 833