复式薄壁方钢管混凝土构件受弯性能研究

通过复式薄壁方钢管混凝土构件受弯性能的试验研究，分析了内置圆形截面空钢管和钢管高强混凝土对薄壁方钢管混凝土构件纯弯段受弯性能的影响。试验表明：内置圆形截面空钢管和钢管高强混凝土可有效提高构件的受弯承载力，内置钢管高强混凝土的提高效果更显著；薄壁方钢管混凝土的受弯承载力和抗弯刚度明显较对比空钢管的高；试验过程中未出现钢管角部破坏的情况。对复式薄壁方钢管混凝土纯弯构件受力性能进行有限元分析，分析结果和试验结果吻合较好，外管的约束作用有效提高了夹层混凝土转角处混凝土的抗压强度。有限元参数分析结果表明，构件的受弯承载力和抗弯刚度随着夹层混凝土强度和径宽比的增大而增大，但随着径厚比的增大而减小；同时构件的受弯承载力随着钢管强度的增大而增大。建议了复式实心薄壁方钢管混凝土构件和复式空心薄壁方钢管混凝土构件受弯承载力的简化计算模型，其计算结果精度较高。

Flexural behavior of composite concrete-filled square thin-walled steel tubular specimens

The tests of composite concrete-filled square thin-walled steel tubular (CCSTWST) specimens under bending load were carried out. The effects of embedding hollow circular steel tube and embedding high-strength concrete filled circular steel tube on the bending behavior of the pure bending segment of the CCSTWST specimen were investigated. The test results indicate that embedding hollow circular steel tube and embedding high-strength concrete-filled circular steel tube can significantly enhance its flexural resistance, and the effect of the later is more obvious. The strength and stiffness of a square CCSTWST is obviously higher than the pure steel tubular counterpart. During the whole testing process, no failure at the corner of the outer steel tube can be found. The FE analysis of the flexural behavior of composite CCSTWST beams were then conducted. The predicted results agreed well with the measured results. The compressive strength of the sandwiched concrete at the corner was effectively increased due to the confinement of the outer steel tube. The parameteric analysis indicates that the flexural resistance and stiffness of CCSTWST specimens are increased with the increase of the sandwiched concrete strength and the ratio of diameter to width. However, the flexural resistance and stiffness are decreased with the increase of the ratio of diameter to thickness. And the flexural resistance of CCSTWST specimens is increased with the increase of the steel yield strength. Finally, the simplified models were proposed to calculate flexural resistances of CCSTWST specimens with a hollow section or a solid section, which have a high accuracy.