Numerical investigation on circular concrete-filled double skin steel tube columns under torsion

Abstract

This paper presents a finite element analysis (FEA) on the torsional behavior of circular concrete-filled double skin steel tube (CFDST) columns. A refined finite element model was established and verified by the test results of circular CFDST columns subject to torsion. The comparison results show that the finite element model can reasonably predict the torsional behavior of circular CFDST columns. Then, parametric analysis was conducted to investigate the effect of key parameters including concrete strength, yield strength and steel ratio of the outer steel tube, yield strength and thickness of the inner steel tube, and the hollow ratio on the torsional capacity of circular CFDST columns. The effect of end constraint, i.e. aspect ratio on the torsional capacity of circular CFDST columns was also discussed. When the aspect ratio is greater than 1.0, the aspect ratio has little effect on the torsional capacity and ductile deformation of circular CFDST columns. Yield strength and steel ratio of the outer steel tube have a great influence on the torsional capacity of circular CFDST columns, but the influence of concrete strength on the torsional capacity of circular CFDST columns is not obvious. Increasing the yield strength and thickness of the inner steel tube can effectively improve the torsional capacity of the circular CFDST columns when the hollow ratio is greater than 0.6. Finally, design formulas were proposed to predict the torsional capacity of the circular CFDST columns, and the comparison results show that the proposed formula has good accuracy.