Question

A 20kN load was hung by a triangular truss as shown below. The member AB and AC are cylindrical solid bar with diameter 25mm. Assume all joints are pinned. Please choose one of the materials below for member AB and AC with reference to the following material properties. (Unless specified, all dimensions are in millimetres) (14 marks) 3000 20kN - 4000 Compressive Strength (N/mm²) | 50 Material 101 102 103 Tensile Strength (N/mm) 70 86 56 60 56

Answer 1

Answer: diameter of solid bar d= 25mm 3000 Aso 0 = tan-'(-3000) 0 = 36.87 20 KN tano-3 sinou 3 , Cosos ♡ Joint A: whese FAB FAB FACA Internal force in solid bar AB Internal force in solid bar AC - - - Equelibrium in y-direction: ZOKN => - {fy=0 FACsino - 20 - O FAB = 20 Faces - - en KM $ Tension ? FAB = 100km 3 Equlibrium in x-direction: FAC + FPBcOSO = 0 FACE - FAB woso V

=> Face - 100x - - BORN 3 FAC=- 80 ş Negative sign indicates FAC will be . compressive in nature FACE got x compression ? Stress developed in solid bar AB GABE / FAO 3* TI * 252 = 67.9 Mmm? | SAB= 67.9 N/mm2 { Tension}) Pensile stress developed in soled bar AB > 56 N/mm2 and nearly to 20 N/mm2 So, choose material of sold bar AB 102 Stress developed in solid bar AC GAC= _FAC - Area - 80 x 100 = 54.3 M/mm2 1. 32. 1 x 25?. JAC=54.3 N/mm2 { compression}]

> SON/mm2 and Compressive stress developed in solid bar ac nearly to 56 N/mm2 So choose material of solid bar ACT 102 Answer: A for 102 AB so led bar An, sold bar and AC for Material