带肋冷弯薄壁方钢管混凝土柱滞回性能研究

对3根带肋冷弯薄壁方钢管混凝土柱进行滞回试验，主要参数为轴压比。试验结果表明：纵向加劲肋有效延缓了钢管壁局部屈曲的发生；其滞回曲线饱满，具有良好的耗能能力；随着轴压比的增大，柱承载力略有增大，而延性、耗能能力则明显减小；当横向位移大于6倍的屈服位移时，大轴压比的刚度退化速度最快。建立了该类试件的有限元模型，对比可得有限元模拟结果与试验结果吻合较好。基于有限元模型对该类构件开展机理分析和参数分析。结果表明：在带肋冷弯薄壁方钢管的约束下，核心混凝土的强度得到了较大提高；钢管局部屈曲发生在峰值荷载后，局部屈曲只发生在纵向加劲肋和钢管角部间；材料强度、轴压比、钢管宽厚比和长细比等参数对该类构件的承载力有较大影响；混凝土强度、轴压比和长细比对荷载-位移骨架曲线形状有较大影响。基于参数分析建议了该类构件的简化滞回模型，简化计算结果和有限元计算结果吻合较好。

Hysteretic behaviour of concrete-filled square cold-formed thin-walled steel tubular beam-columns with longitudinal stiffeners

The hysteretic tests of three concrete-filled square cold-formed thin-walled steel tubular (CSCTST) specimens with longitudinal stiffeners were carried out. The main experimental parameter was axial compressive ratio. The experimental results indicate that the local buckling of the steel tube is delayed by longitudinal stiffeners. The hysteretic curves of composite columns are plump. This composite column has a good energy dissipation capacity. With the increasing of the axial compressive ratio, the lateral load-bearing capacity of specimens increases slightly, but the ductility and energy dissipation capacity decreases dramatically. When the lateral displacement is beyond 6 times of yield displacement, the specimen with the largest axial compressive ratio achieves the highest speed of stiffness degradation. The finite element (FE) model of the CSCTST specimen was developed. Through a comparison, it can be found that FE results agree well with test results. The mechanism analysis and parametric analysis of CSCTST columns were conducted using the FE model. It can be found that the concrete strength can be effectively enhanced due to the confinement of the square cold-formed thin-walled steel tube with longitudinal stiffeners. The local buckling of the steel tube is observed after the peak load. The steel tube buckling only occurrs between the longitudinal stiffener and the corner of the steel tube. The strength of this composite specimen is significantly affected by parameters including the material strength, axial compressive ratio, width to thickness ratio of the steel tube and slenderness ratio. The shape of the load versus displacement skeleton curve of the composite column is affected by parameters including the concrete strength, axial compressive ratio and slenderness ratio. Based on the parametric analysis, the simplified hysteretic model was proposed for this composite column. The predictions using the simplified hysteretic model agreed well with the FE results.