Question

Problem 3-4 (20%) Please write Pb 3-4 on top of your submission sheet for this problem Fy Fx C All members are steel circular rods Es=200 GPa Diameter = 40mm L = 2.0m H= 1.0m Fx =Fy = 20KN (A) What is the factor of safety against buckling for this truss?

Answer 1

Step I Analysis of truss By E2m 20kn 2010 Max Time Hlm Y t tamo= ½ Ax to coso = 1 / Sint = Fs • Finding reactions ; ů { Fy=0 By-20 20 By=201001 co met moment at AzO EM AO J _ BX X1 +20x2 -20x120 =) Bx=20 kNE Cío {fxzo > Ax-Bx-2020 = A x=40 KN • Joint B By Z0 KN Tx Bee Foc EF, = 0 Foc- B x =0 > foc=20KN ETT 220K 20 KN {fy =O - FABt By co =far=20kw (1) 20 KN Jointa 20 KN Ex Face 20kn oth 20kn {fy=0 oc facsin 0-20 KN=0 FAcXL = 20KN (fac = 20 55 kN (C)

Notel so out of 3 members (AB, AC & BC) only AC is having compressive force so only Al' can have buckling as AB, BC have tension so no buckling in AB & BC I only AC is having compressive force & fac= 2055 kN] length of AR, LAC= V1+2= = 15m diameter, d=0,04m. Es=200 GPa = 200x109 Alma 1. Both ends of ac are hinged so critical buckling load of AC so Left = Lacrom PORAL= T²E Inc 12 64 64 Moment of inertia, Jacz AdaAX(0.04), 47x10m4 Per ac= 7²x 200 x100x (4*X108)_49610.04 N (rs)2 (PAC = 49.610 kN - Using 0 , FAC=2055 = 44.72 KN (A) factor of safety against buckling = critical drucking load (Per) 3 Actual Condacting CFAC) fos = 4.4.6.1 - 1.1093 I factor of safety against buckling = 1.1o.