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. © 2020, Editorial Office of Journal of Building Structures. All right reserved.