Numerical modeling of axially loaded circular concrete-filled double-skin steel tubular short columns incorporating a new concrete confinement model

The accurate prediction of the concrete confinement effects in concrete-filled double-skin steel tubular (CFDST) columns composed of a circular section is vital in stimulating their true structural performance. However, existing concrete confinement models for such columns were developed based on limited studies and may not accurately predict their axial responses under axial loading. In this paper, a numerical model is developed to study the nonlinear performance of axially-loaded short CFDST columns incorporating an accurate concrete confinement model. Herein, a novel expression to calculate the lateral confining pressure on the confined concrete of the CFDST column is proposed considering the influences of a wide range of important column parameters. Furthermore, a reduction factor to accurately predict the post-peak behavior of confined concrete is suggested based on the previous test results. The accuracy of the numerical model incorporating the proposed concrete confinement model is verified against the experimental tests. The accuracy of the existing concrete confinement models is also evaluated and compared with the one proposed in this study. It is demonstrated that the proposed confinement model can yield the axial performance of CFDST columns more accurately. A parameter study is then performed to analyze the impacts of important column parameters on the axial performance of such a column. The applicability of the existing design standards in designing CFDST columns is verified. Lastly, a simple and accurate design equation to quantify the ultimate axial load is proposed.