Tests on residual ultimate bearing capacity of square CFST columns after impact

This paper presents a study on the mechanical performance of the square concrete-filled steel tube (CFST) columns under the axial compression, which is based on forty-eight short square CFST columns subjected to lateral impact. The concrete compressive strength, impact energy and impact location are set as the parameters in the test. This paper mainly analyzes the effect of these three parameters on the residual ultimate bearing capacity of the test specimens. The result indicates that the lateral impact has negative influence on the residual ultimate bearing capacity, initial stiffness and ductility of the CFST columns. The impact location has a significant influence on the residual ultimate bearing capacity. The residual ultimate bearing capacity decreases as the impact location varies from the middle-length to the end of the specimens. The test result indicates that the lateral impact causes an evident decrease of the ductility and initial stiffness of CFST columns. Ductility increases as the impact location varies from the middle-length to the end of the specimens. Besides, the strain development of twelve square CFST columns during the experiment is investigated in this paper. Based on the experimental results, a calculation formula is proposed to predict the residual ultimate bearing capacity for the specimens tested, and a good agreement with the experimental results is achieved.