Question

ma Problem 6.60 Determine the force in the members AB, AE, BC, BF, BD, and BE of the space truss. Sharing 4 ft A ft ngs 2 ft 4 ft 600 lb ols 2 ft 300 lb 400 I Part A Determine the force in member AB P N

Answer 1

2 ft 4 t 600 lb 300 lb 400 lb Method of Joints: In this case, there is no need to compute the support reactions. We will begin by analyzing the equilibrium of joint A, and then that ofjoints Cand B Joint A: From the free - body diagram, Fig. a FAE 300 0 Ans. FAE 450 lb (T) 4. -FAD 20 0 EF = 0; 600-450 FAD = 335.41 lb (T) Fy = 0; FAB - 335.41 20 450 Ans. = 300 lb (T) FAB Joint C: From the free -body diagram of the joint in Fig. b, notice that FaD, FOF, and Cv lie in the y -z plane (shown shaded). Thus, if we write the force equation of equilibrium along the x axis, we have 4 = 0 20 Ans. FRC 0 Joint B: From the free -body diagram, Fig. c, 4 0 - FBD52 (1) |- FBE68 F 0; -FBF (a) 6 -F BDT 68 (2) -300= 0 - FBE УFy 3 0; FвF 4. +FBF (3) 400 0 BE68 Solving Eqs. (1) through (3) yields Ans. FRE 225 lb (T) Ans. FRE = 515.39 lb = 515 lb (T) Ans. FRD-721.11 lb =721 lb (C)

4ft FBE FAE 4ft Fep FAB 300 FaP A boolb 4ft FAB 300lb 4001b Ca) FeF FD 4ft Cas C 2ft (b) NN