拉筋钢管混凝土柱轴压力学性能研究

Experimental study on stirrup-confined concrete-filled steel tubular stub columns under axial loading

拉筋钢管混凝土短柱较其他组合结构短柱具有更高的承载力及延性。为提出适用性更广的拉筋钢管混凝土短柱轴压极限承载力计算方法,探究拉筋连接模式和等效体积配箍率对拉筋钢管混凝土柱轴压力学性能的影响,利用约束混凝土本构关系,建立焊接和非焊接拉筋钢管混凝土短柱轴压及不同截面形式拉筋钢管混凝土短柱轴压的数值模型。对16根不同截面及拉筋型式钢管混凝土短柱进行轴压试验研究,验证数值模型的准确性及适用性。在此基础上,探究拉筋钢管混凝土约束作用及约束区域,提出适用性更广的拉筋钢管混凝土短柱轴压承载力计算公式。研究结果表明:基于约束混凝土本构模型的数值分析方法可有效模拟焊接及非焊接型式拉筋钢管混凝土短住轴压受力性能。焊接及非焊接拉筋对钢管与核心混凝土有明显的约束作用,且拉筋对方形截面钢管混凝土短柱轴压承载力的影响大于圆形截面钢管混凝土短柱。相较于方形截面拉筋钢管混凝土短柱,等效配箍率对圆形截面短柱轴压承载力的影响较小。焊接试件拉筋应力较非焊接试件增加早且快,对核心混凝土的约束作用强。另外,所提拉筋钢管混凝土短柱轴压承载力计算公式对不同截面形式构件均有较好的适用性,计算结果与试验结果吻合良好,精度较高且偏于安全。

The stirrup-configuration concrete-filled steel tubular(CFST)short columns have higher bearing capacity and ductility than other short composite columns.To propose a more applicable calculation method for the ultimate axial bearing capacity of CFST short columns,and investigate the effects of the stirrup connection mode and equivalent volume stirrup ratio on the axial compressive properties of the stirrup-confined CFST short columns,the numerical models of welded and non-welded stirrup confined CFST short columns with different section forms were established based on the constrained concrete constitutive model.The accuracy and applicability of the numerical model were verified by the axial compression tests on 16 CFST short columns with different cross sections and stirrups.The constraint effects and constraint area of CFST short columns were studied,and a more applicable formula for calculating the axial bearing capacity of CFST short columns under axial compression was proposed.The results indicated that the numerical analysis method based on the constrained concrete constitutive model can effectively simulate the axial compressive properties of welded and non-welded stirrup-confined CFST short columns.The welded and non-welded stirrups both have obvious constraint effects on steel tube and core concrete.The influence of stirrups on the axial compression capacity of square section CFST short column is greater than that of circular section counterparts.Compared with square section columns,the effects of equivalent stirrup ratio on the axial bearing capacity of the circular section short columns is less.The tensile stress of welded stirrups increases earlier and faster than that of non-welded specimens,which has a stronger constraint effect on core concrete.In addition,the formula for calculating the axial bearing capacity of the stirrup-confined CFST short column has good applicability to the members with different section forms,and the calculated results are in good agreement with the experimental results,with high accuracy and safety.