Question

. Determine (approximately) the force in each member of the truss. Assume the diagonals can support both tensile and compressive forces. (15 marks) 8 kN 2 10 kN 冫 2 A symmetrical frame structure with two pined ends (A" and "H") is shown in the following figure Two lateral concentrated loads P-20kN acting at po 6.

Answer 1

Method of sections It is required that F_CE = F_DF = F-1 sigma F_x = 0 8 - 2F_1 (3/5) = 0 F_1 = 6.667 kN Therefore F_CE = 6.67 KN (c) F_DF = 6.67 KN (T) sigma M_E = 0 F_CD (1.5) - 6.667 (4/5) (1.5) = 0 F_CD = 5.333 KN (c) F_CD = 5.33 KN (c) sigma M_D = 0 F_EF (1.5) - 6.667 (4/5) (1.5) = 0 F_EF = 5.333 kN (T) F_EF = 5.33 kN (T) It is required that F_BF = F_AC = F_2 sigma F_x = 0 8 + 10 - 2F_2 (3/5) = 0 F_2 = 15 kN Therefore F_BF = 15 kN (c) F_AC = 15 kN (T) sigma M_F = 0 F_BC (1.5) - 15 (4/5) (1.5) - 8(2) = 0 F_BC = 22.67 FN (c) F_BC = 22.67 kN (c) sigma M_C = 0 F_AF (1.5) - 15 (4/5) (1.5) - 8(2) = 0