Question

1) (100) For the following truss Determine the horizontal and vertical components of the reaction at pin C, and the a. reaction at roller F required to support the truss. Use the method of joints to find the internal forces of each member b. Assuming the maximum allowable tensile stress is 36 ksi and the maximum allowable C. compressive stress is 30ksi what is the required cross sectional area? Assume each member has the same cross sectional area. A 20 k 6' D 45° 30 k 30 k 8' 8'

Answer 1

Sof Jam a = %3D Sino= ")45" CosQ> 30K 30K. 8' FBD 20K 30k

- 30 (16) -30(8) + Re (6) > 0 he=12052 K Rf 20+ Cx + Cx = - 120 - 20 140 k - 30 - 3 O + Cy + - 60 120 1y= member foices member faces are in temsion A - he + ve aue in tunnion { fy=o fcF = Cy = - 60K = 140 k fCB

At joint D Efy=0 For 1FDA= 30k FoE 30 At joint A FAe 20 FAD { fx = 0 20 = FAe t Far cos Q A E Efy= 0 FAo + FAE SinO 30+ FAE 3 FAR= sOK Rutting fAe in ey O - FAs + (-50) fAB

At joint E E Fx= 0 FEA FeB FEF fEAcesQ + fED FEF -Sox4 FED TFEE: - чо к %3D EFy= 0 fEe + FEA Sino = 30 FEB + (-50)x FER = 60k At joint B fac Foct fepcono FeA FBE 140 + Fof x4 [Fef = -l00k 36 Kai <) allowable max tusile stiey = 30ksi allowakle max compienine strey = 140k Maximum tesile faice= Maxinum complemsine forie = %3D for tunile) 36 ? 140 A 3.889 in

for compesion 302 l00 A 2 3.33 in each member has s ame costedional aea memba aos sectional arla l member is of alea A =| 3.889 in uprofe Pleare :)