Torsional capacity of concrete-filled steel tube columns circumferentially confined by CFRP

Abstract The concrete-filled steel tube (CFST) column circumferentially confined by carbon fibre reinforced polymer (CFRP), i.e. CFRP-CFST column, is a promising structural member in engineering practice. In this paper, the torsional capacity of CFRP-CFST columns was investigated by means of finite element (FE) simulation and theoretical derivation. Comprehensive FE models were established considering suitable material constitutive laws and interface relationships, which were then verified by experiment results. Besides, parametric analysis was conducted to reveal the geometrical and material parameters' effects on the torsional capacity of CFRP-CFST columns. The results show that the yield strength, the thickness, and the outer diameter of the steel tube are the most influential factors, and the number of CFRP layers also affects the torsional capacity considerably. Meanwhile, the comparison between the CFRP-CFST and CFST column indicates that the confinement effect provided by the CFRP can enhance the torsional capacity. Finally, equations for calculating the torsional capacity of the CFRP-CFST column were proposed and proved to be accurate through comparison with the test data.