Question

Please use figure 1B since i am in an even number group

1. Purlin Design Purlins are beams designed to carry roof loads. The roof purlins are usually inclined and carry vertical loads due to dead load and live load and normal loads due to wind. Hence the purlin sections are subjected to unsymmetrical bending, Assume that the purlins are simply supported with span length, L = 3.0 m and carry uniform vertical load w. The allowable stresses in tension and compression are 125 MPa and 150 MPa, respectively. The regular Z and C steel section have the dimensions shown. You are required to determine which shape (regular Zor C) or (Inverted Zor C) can carry the larger uniform load w. (a) Fig 1A-ODD Number Groups (Inverted sections) (b) Fig 1B-EVEN Number Groups (Regular sections) Fig. 1B Fig. IA AINT = 15 deg = 15 deg 12 mm WIIIIIIIIIIAL 150 mm 12 mm 180 mm 180 mm 12 mm 12 mm 12 mm + 12 mm 150 mm 150 mm

Answer 1

puulins ce simboly supported with span length = zom And carry uniform load - W Mx = WNL where My is Max.B.M ws Zx = Section Modules Zx = I SY Thx - permissible or allowable stress box- Simik My = WIL MOI Zy- I - Te Externe fibre distance by = my Note: Tot = obx to by allowable for Concept is greater the section Modules z goberno lesser will be the stresses produced more resistance to Load

"So check for section modules Greater value of section modules 1 more resistande capacity to load Figla A150 ISO 12mm mm L2mm 12 mm WW=Wcoso WT = Wsino

S uso want have Monsent of Resistance - o (stress) x 2 (Section 1 AT Modulus.) Moment of Resistance will be more for fig 1A. By changing sections of moment of Resistance will change or effected.