冷弯薄壁型钢四肢拼合箱形柱偏压受力性能试验研究与数值分析

对冷弯薄壁型钢四肢拼合箱形截面立柱进行轴压和偏压试验研究，得到各试件的荷载-位移曲线和极限承载力，详细分析了试件的屈曲模式和破坏特征。建立了考虑材料、几何和接触非线性的有限元模型对试验试件进行模拟分析，两者吻合较好，验证了有限元方法的正确性。进而采用数值方法分析了构件长细比、螺钉间距和位置、偏心距和偏心方向对该类拼合立柱偏压受力性能的影响。结果表明：双向刀铰支座可以很好的实现铰接；螺钉间距为300mm时，拼合柱各肢整体协同工作性能良好；轴压和绕弱轴偏压试件最终破坏模式均为绕弱轴整体弯曲，绕强轴偏压时，试件破坏模式为弯扭失稳，但扭转不明显；拼合柱的偏压极限承载力和刚度随长细比和偏心距的增大而降低；偏心距相同时，拼合柱绕强轴偏压的极限承载力和刚度比绕弱轴偏压略高。

Experimental study and numerical analysis on cold-formed thin-walled quadruple-limb built-up box-section columns under eccentric compression

 To investigate the buckling modes and failure characteristics of cold-formed thin-walledsteel quadruple-limb built-up box-section columns, column specimens were tested under axial andeccentric compression, respectively. The load-displacement curves and ultimate bearing capacity ofspecimens were obtained. The finite element models considering material, geometry and contactnonlinearity were also built to simulate and analyze the specimens. The results of FEM agree wellwith the test results, validating the reasonability of finite element method. With the finiteelement models, the influences of slenderness ratio, spacing and location of screws, eccentricityand eccentric direction on the eccentric mechanical behavior of these columns were studied. Theresults show that the hinge joint can be simulated by double knife-edge support very well. Thoselimbs of built-up columns can work in collaboration with each other when the spacing of screws is300mm. The failure mode of specimen in axial compression or in eccentric compression around weakaxis is the overall flexural buckling. The failure mode of specimen in eccentric compressionaround strong axis is the flexural-torsional buckling, but the torsion effect is not obvious. Theultimate bearing capacity and stiffness of built-up columns in eccentric compression may decreasewith the increase of slenderness ratio or eccentricity. With the same eccentricity, the ultimatebearing capacity and stiffness of built-up columns around strong axis are slightly higher thanthose of columns around weak axis.