中文摘要：

提出了适用于带约束拉杆方形钢管混凝土短柱有限元分析的核心混凝土单轴应力-应变关系模型;基于ABAQUS大型通用有限元平台,考虑试件受力过程中多种材料泊松比变化及本构关系非线性等因素,编写了USDFLD子程序,并建立了带约束拉杆方形钢管混凝土短柱的有限元模型;从应力-应变关系,钢管、核心混凝土及约束拉杆三者之间的约束作用、核心混凝土纵向应力分布等方面讨论了带约束拉杆方形钢管混凝土短柱的工作机理.结果表明：采用文中提出的有限元模型模拟得到的结果与试验结果吻合较好;设置约束拉杆能够减缓并延迟钢管的向外局部屈曲,使钢管屈服发生在极限承载力之前,增强钢管角部和中部对核心混凝土的约束作用,提高核心混凝土的纵向应力,从而提高试件的承载力和延性;随着约束拉杆间距的减小,钢管角部和中部对核心混凝土的约束作用明显增大.

英文摘要：

In this paper,first,a uniaxial stress-strain relation of the core concrete is proposed for the finite element （FE） analysis of the square concrete-filled steel tubular （CFST） stub columns with binding bars.Then,based on the ABAQUS FE platform,a USDFLD subroutine is presented by considering the Poisson ratio changes and the nonlinear constitutive relation of many materials in the loading process,and a FE model is then established to simulate the square CFST stub columns.Finally,the mechanical behavior of the square CFST stub columns is discussed in terms of the stress-strain relation and the confined effect among the steel tube,the core concrete and the binding bars,as well as of the longitudinal stress distribution of the core concrete.The results show that （1） the computation results obtained through the proposed FE model accord well with the test results; （2） the binding bars can delay the local buckling of the steel tube and thus make the steel tube yield before the ultimate strength of the specimen occurs,and they can also improve the concrete confinement of the corner and central regions and thus increase the longitudinal stress of the core concrete,so that the bearing capacity and ductility of the specimen can be improved; and （3） the concrete confinement of the corner and the central regions increases with the decrease of the spacing between the binding bars.