Compressive behaviour of circular CFDST short columns with high- and ultrahigh-strength concrete

Abstract

Concrete-filled double-skin steel tubular (CFDST) columns possess lower self-weight, higher ductility and energy absorption than conventional concrete-filled steel tubular (CFST) ones. The use of high-strength concrete (HSC) can further enhance their advantages, such as greater mechanical and economical benefits. However, there is little information on the structural performance of CFDST columns with HSC, especially ones with ultrahigh-strength concrete (UHSC). In this paper, a comprehensive experimental program consisted of 24 specimens was carried out to investigate the compressive behaviour of circular CFDST short columns with HSC and UHSC. The test results show that CFDST columns with higher strength concrete generally achieve higher initial stiffness and axial strengths but lower ductility. Additionally, the axial strengths of CFDST columns are improved as the yield stress and wall thickness of the outer steel tubes increase and as the hollow ratio decreases. A finite element (FE) model was established and verified against the present test results, based on which the interaction of the steel tubes and concrete and the load distribution on components were analysed. A parametric study using the verified FE model was conducted to further ascertain the influences of column variables on the compressive behaviour of the studied CFDST columns. Finally, the applicability of the existing design codes and empirical models to design the CFDST columns was evaluated based on the test results in the present and previous studies. It is shown that European code EN 1994−1−1 (EC4) achieves better strength predictions than other design models.