Axial compression performance analysis and bearing capacity calculation on square concrete-filled double-tube short columns

Abstract

The concrete-filled double-tube (CFDT) columns have been proposed in recent years. The existence of inner steel tube can not only increase the confinement on core concrete, but also increase its fire resistance and anticorrosion performance. This makes it have a great application prospect in the field of ocean structure engineering. In this paper, the axial compression performance of square CFDT short columns is comprehensively analyzed. The specimens studied consist of an external steel tube (square hollow section) and an inner steel tube (circular hollow section), in which concrete is completely filled. The fine finite element (FE) method is used to simulate the performance of this column. Two constitutive models of confined concrete for square CFDT core concrete are proposed. In order to ensure the correctness of the model, the verification analysis of the model is carried out based on the previous experimental results, and the whole process of axial compression performance of CFDT columns is analyzed in detail. The concrete strength (fc'), width-thickness ratio (B/to), diameter-thickness ratio (d/ti), diameter-width ratio (d/B) and yield strength (fy) of square CFDT columns are compared and analyzed. The performance of CFDT columns with the same steel content is also analyzed, it is of great significance to improve the application of CFDT columns in marine environment or high temperature environment. Finally, new formulas for calculating the ultimate bearing capacity of CFDT short columns under axial compression are proposed. The results show that the new formulas can predict the strength of CFDT short columns well.