方钢管混凝土不等端弯矩偏压柱力学性能研究

以端弯矩比、长细比和荷载偏心距为主要变化参数，进行了12个方钢管混凝土不等端弯矩偏压柱试验研究。试验结果表明：对于长细比为40.1的试件，端弯矩比对试件破坏形态影响很大，端弯矩比为-1的试件挠曲线为S型，而端弯矩比为1的试件挠曲线为正弦半波；而对于长细比为20.6的短柱试件，端弯矩比对试件破坏形态影响不明显；长细比和偏心距越大，承载力越小；随端弯矩比β从-1~1变化，试件承载力逐渐减小。采用两种计算方法对试件承载力进行了计算，并与试验结果进行对比，计算结果总体低于试验结果。采用有限元软件ABAQUS对方钢管混凝土不等端弯矩偏压柱的受力全过程进行分析，计算得到的试件破坏形态与荷载 变形关系曲线均与试验结果吻合良好。在此基础上，对3种不同端弯矩比的典型算例进行计算，从试件的变形情况、荷载-变形全过程曲线、核心混凝土纵向应力分布及钢管与核心混凝土的相互作用等4个方面对方钢管混凝土不等端弯矩偏压柱的工作机理进行对比分析。研究结果表明：随着端弯矩比由-1~1变化，试件的侧向挠度增大，核心混凝土承担荷载降低，试件承载力降低；所有试件的钢管均表现出良好的约束性能。

Mechanical behavior of concrete-filled square steel tubular columns subjected to eccentric loading of unequal end-moment

Tests of 12 concrete-filled square steel tubular columns subjected to eccentric loading of unequal end-moment were carried out. The main test parameters were end-moment ratio, slenderness ratio and loading eccentricity. The results of tests show that the end-moment ratio has significant effect on the failure modes of composite specimens with slenderness ratio 40.1. The deflection curve looks like S when end-moment ratio of specimen is -1, while the deflection curve coincides with half sine wave as end-moment ratio of specimen is 1. For specimens with slenderness ratio 20.6, there is no significant impact on failure modes with the changes of end-moment ratio. With the increases of the slenderness ratio and eccentric distance, the bearing capacity of specimen reduces. When the end moment ratio of specimens changes from -1 to 1, the bearing capacity reduces. The bearing capacities of specimens were calculated by two kinds of formulas and compared with the test results. The overall calculated results are lower than the test results. The load-deformation of concrete-filled square steel tubular columns under eccentric loading of unequal end-moments was analyzed by finite element method. The calculation results were in good agreement with the experimental results. On this basis, the behavior of the columns was analyzed from the following four aspects such as the lateral deflection development, load-displacement curves, longitudinal stress distribution of concrete, and the interactions between steel and concrete. Three typical composite columns were then compared with working mechanism. The studies show that the deformation of composite columns will increase with the end-moment ratio of composite columns changing from -1 to 1, while the bearing capacity of composite columns will reduce. The steel tubes of all composite columns provide good confinement performance.