Week 4 Challenge

a) ISMB 500

b/tf=180/172=10.46<10.6

hence section is compact

b) ISMC 200

b/tf=75/11.4=6.57<9.4

hence section is PLASTIC

c) PG 1300X450X20X12

b/tf=450/20=22.5>29.3

hence section is PLASTIC

d)2 ISA 75X75X6

b/tf=75/6=12.5<15.7 >10.5

hence section is semi compact

e) RHS 150X100X10

d/tw=150/10=15<54

hence section is PLASTIC.

f) Builtup box 1000x450x20x12

d/tw=1000/12=83.3<84

hence section is PLASTIC.

2) a) Effective length of top chord1=0.85L1

Effective length of top chord2=0.85L2

Effective length of vertical member=0.85L3

Effective length of inclined member=0.75L4

b) Length of rafter

Effective Length of rafter=0.85L=0.85X20.7=17.6M

Result=The effective length of beams has been calculatedaccording to table 16 IS 800

3)Deflection of centre

Y=WL³/48EI=[3a1/L-4(a1)³/L]+WL³/48EI[3a2/L-4(a2)³/L]X5WL³/384EI

Y=100X7³/48X20X106X[3X2/7-4(2)³/7]+100X7³/48X20X10X[3X5/7-4(5)³/7]X5X6X7³/384X20X106

Y=0.0536mm

b)Y=WL³/48EI=[3a1/L-4(a1)³/L]+WL³/48EI[3a2/L-4(a2)³/L]X5WL³/384EI

Y=2000X5³/48X20X106X[3X2.5/5-4(2.5/5)³]+5/384X1500X5³/20X106

Y=0.782mm

c) Y=5mm

Y=5WL³/384EI

EI=5WL³/384Y

=5X10X1000X10³/384X5X10³