BENDING AND TWISTING ABOUT A CONSTRAINED AXIS OF Z-SECTION PURLINS WITH ONE SAG ROD AT MIDSPAN

The sag Rods connected to the webs of puRlins weRe RegaRded as the lateRal elastic suppoRts of the puRlins. The formulas for calculating the Rigidity of the sag Rod weRe established by deRiving the web deformation of the puRlin accoRding to the theoRy of plate and shell，and then the Rigidity of the sag Rod taking account of the web deformation was got，which was modified by FE analysis. It was found that for a Z-section puRlin undeR wind suction，the Reaction within the sag Rod was small. Hence theRe would be a veRy limited effect on the stRess，and also a small distoRtional deformation of the sag Rod section if the sag Rod was simplified as a lateRal Rigid suppoRt oR elastic one. FoR the Z-section the calculated stRess would have excellent accuRacy when the EC3 method，two-way bending method and the method of one-way bending about the paRallel axis weRe used.