Performance analysis and bearing capacity calculation on circular concrete-filled double steel tubular stub columns under axial compression

Abstract

Concrete-filled double steel tubular (CFDST) columns have been proposed in recent years. This paper presents the performance analysis and a new bearing capacity calculation method of circular CFDST stub columns under axial compression. In order to establish accurate finite element (FE) model, various constitutive models for both the concrete infill and steel tubes are analyzed and compared with experimental results in FE analysis, and the suitable constitutive models for sandwich concrete, core concrete and steel tube are proposed in the FE model developed. Based on the validated numerical model, the variation of confining stress between steel tube and concrete is analyzed in detail. In addition, parametric studies are conducted to investigate the effects of concrete strength, external tube thickness, inner tube thickness, diameter ratio of inner tube to external tube and yield strength of steel tube on the axial compressive performance of circular CFDST stub columns. A new simplified formula based on the confining pressure is proposed to evaluate the ultimate bearing capacity of the circular CFDST stub columns. Based on the comparisons with experimental results and numerical simulation results, it is shown that the proposed formulae for the circular CFDST stub columns appear to be satisfactory.