Simplified Formula Algorithm Of The Critical Loading Of Z-purlin Braced By The Skin Diaphragm Under Wing Suction Effect

Purlin is always suffering lateral support and torsional restraint from the roof sheeting in the practical application, which is called bracing effect of skin diaphragms. Considering that effect can effectively reduce the economic costs during the engineering design. However, the current design algorithm of a relevant Chinese code for the bearing capacity of purlin braced by the skin diaphragm under wind suction effect is too complicated that decrease design efficiency greatly.This paper introduce the classic finite element model, then four parameter analyses are conducted under wind suction effect on the cratical loading of lateral buckling for Z-purlin,and the four parameters are purlin web depth-thickness ratio 、purlin flange width-thickness ratio、 purlin lateral slenderness ratio 、torsional restraint stiffness. Finally, a simplified calculation formula of the critical loading of Z-purlin which considering the diaphragm effect under wind suction effect is obtained.The accuracy of the formula is testified by comparing the result of simplified formula algorithm with the result of relevant Chinese code method and finite element analysis.The relationship between purlin distance and torsional restraint stiffness is analyzed with finite element method. Then 2394 simplified finite element models are established according to the torsional restrant test to calculate the torsional restraint stiffness that the torsion restraint stiffness table included, and the problem with the application of the simplified formula algorithm is solved.And compared with above code method, the calculation process of the simplified formula algorithm is very simple, so that it can improve the efficiency of engineering design greatly.