弯-剪-扭耦合荷载作用下钢管混凝土短柱受力性能研究

为研究钢管混凝土短柱在剪切和扭转复合作用下的受力性能，开展了10个钢管混凝土短柱试件在纯扭、弯-剪和弯-剪-扭荷载作用下的拟静力往复加载及单调加载试验，得到了钢管混凝土短柱的荷载-变形曲线和钢管应变分布规律。试验结果表明：钢管混凝土短柱具有良好的承载能力和塑性性能；在纯扭作用下，圆形钢管混凝土短柱在往复扭转荷载作用下钢管发生低周疲劳破坏；方形钢管混凝土短柱在单调及往复扭转荷载作用下钢管面外发生斜向局部屈曲；纯扭往复荷载作用下的钢管混凝土柱的荷载-变形骨架曲线与单调加载下基本一致；在弯-剪及弯-剪-扭复合荷载作用下，在进入塑性工作阶段前截面的轴向变形基本满足“平截面假定”；在弯-剪-扭耦合荷载作用下，短柱的破坏模式取决于弯扭比，在弯扭比较大（为1.90）时，其类似于弯剪破坏，在弯扭比较小（为0.96）时，其类似于扭转破坏。在有限元模拟及大量参数分析的基础上，得到了钢管混凝土短柱的弯-剪-扭承载力相关方程，承载力计算结果与有限元分析结果吻合较好。

Study on mechanical behavior of concrete filled steel tubular short columns under compound bending-shear-torsion load

In order to investigate the mechanical properties and failure mechanism of concrete filled steel tubular (CFST) short columns under compound forces including shear and torsion, the experimental study of ten CFST short column specimens under reversed cyclic and monotonic pure torsion, bending-shear and bending-shear-torsion load was carried out. The load-deformation curve and the strain distribution law of the CFST short columns under reversed cyclic and monotonic loading were obtained. Test results showed that the ultimate capacity and plastic properties of CFST short columns are good. The failure mode of circular CFST short columns under cyclic torsion load is the low-cycle fatigue failure of steel tube, and the diagonal buckling wave appeares on steel tube of square CFST short columns. The skeleton curve of specimens under cyclic pure torsion is similar with that of specimens under monotonic pure torsion. When specimens subject to bending-shear load and bending-shear-torsion load, the axial cross section deformation satisfies the ‘plane section assumption’. The failure modes depend on the bending moment-torsion moment ratio under bending-shear-torsion load. The failure modes of columns are flexural and shearing failure on the larger bending and torsion ratio (1.90) . The failure modes of columns are torsion failure on the smaller bending and torsion ratio (0.96). Then, the finite element simulation and parameter analysis were carried out for obtaining the interaction relation equation of CFST columns under compound bending-shear-torsion load. The results of finite element method and the results of calculation of bearing capacity agree very well.