冷弯薄壁Z形钢梁的双向弯曲和扭转试验研究

Experimental Research on Cold-formed Thin-walled Z-beams Under Biaxial Bending and Torsion

冷弯薄壁Z形截面钢梁在实际工程中受到横向荷载作用时容易发生双向弯曲并且伴随扭转。为此,对跨中偏心集中荷载引起的双向弯曲和扭转联合作用下12根冷弯薄壁Z形钢梁进行静力试验。试验采用两种不同厚度、两种不同跨长的冷弯薄壁Z形钢梁,梁端为简支支座,在跨中施加平行于腹板的竖向集中力,并采用3种不同的偏心距,得到了试验钢梁的破坏形态、极限荷载、荷载-位移曲线。同时对试验钢梁进行了非线性有限元分析,分析结果与试验结果吻合。试验钢梁在跨中偏心集中力引起的双向弯曲和扭转联合作用下,截面发生扭转,同时上翼缘出现畸变屈曲,下翼缘出现局部屈曲。随着偏心距数值的增大,钢梁破坏时的极限荷载值明显降低,受弯承载力相应地降低。根据现行冷弯薄壁型钢结构技术规范(GB50018—2002)的计算公式对试验钢梁的承载力进行了计算,得到的计算结果十分保守。

Cold-formed thin-walled Z-beam is often subjected to biaxial bending and combined torsion actions when it is subjected to transverse loads in practical engineering.This paper conducted tests on 12 cold-formed thin-walled Z-beams under biaxial bending and torsion induced by the action of a mid-span eccentric load.In the tests cold-formed thin-walled Z-beams with two varying thicknesses and two varying spans were used,the beams were simply-supported,the load was applied at mid-span and was parallel to the web with three varying eccentricities.Failure modes,ultimate loads,and load-displacement curves of the tested beams were obtained.Nonlinear finite clement analysis was conducted on the tested beams and the analysis results agreed well with test results.The tested beams failed with section twist rotation,top flange distortional buckling and bottom flange local buckling.As the load eccentricities increase,their ultimate loads decrease obviously and the bending capacities reduce corrcspondcntly.The design equation in the current technical code of cold-formed thin-wall steel structures(GB50018—2002)was used to calculate the load capacity of the tested beams and the calculation results were very conservative.