复合约束方钢管混凝土短柱轴压性能有限元分析

为延缓轴压作用下方钢管的局部屈曲，提高方钢管对核心混凝土的约束能力，提出了一种内置方形箍筋的复合约束方钢管混凝土柱。采用有限元软件ABAQUS对该柱进行模拟，研究其在轴向压力作用下的破坏模式、承载能力、延性、箍筋应力分布和复合约束特性，并分析了混凝土强度、方钢管壁厚对其轴压力学性能的影响。研究结果表明：提高混凝土强度、增加方钢管厚度和增设方形钢筋笼均能显著提高短柱的承载能力；方形箍筋在弹性阶段约束作用较小，其主要在弹塑性阶段和流塑性阶段发挥约束作用，设置方形箍筋可以有效提高短柱承载能力和延性，且其对延性的提高更为显著；方钢管对混凝土的约束作用整体表现为“角部大”的特点，方形箍筋可以有效增强对方钢管边长中部区域混凝土的约束作用，进而使混凝土在各方向受到的约束作用趋于均匀。

Finite element analysis on axial loading behavior of stub column of composite confined concrete-filled square steel tube

A type of concrete-filled square steel tubular columns with square stirrups was put forward to delay the local buckling of square steel tube and improve the restraint ability of square steel tube on core concrete under the action of axial loads. The finite element software ABAQUS was used to simulate the stub columns. The failure mode, bearing capacity, ductility, stirrup stress distribution and composite constraint characteristics under axial loads were studied. The influence of concrete strength and wall thickness on axial loading behavior of the stub columns was also analyzed. The research results show that improving the concrete strength, increasing the wall thickness of the square steel tube and adding square reinforcement cage can improve the bearing capacity of stub columns significantly. The square stirrup has limited restraint effect on the concrete in the elastic stage. However, it mainly plays a constraint role in the elastic-plastic and flow-plastic stage and therefore it can effectively improve the bearing capacity and ductility of the columns. Besides, it has a greater improvement on the ductility. The restraint effect of square steel tube on concrete is mainly characterized by large corner. The square stirrup can effectively supplement the restraint effect of the core concrete in the middle area of the side length of square steel tube, which makes the restraint effect on concrete in all directions uniform.