Behaviours of circular high-strength concrete-filled high-strength steel tubular columns after constant heating

High-strength concrete-filled high-strength steel tubular (HSCFST) columns offer good bearing capacity and stiffness. Currently, there is limited research focused on the residual performance of this kind of member. In this study, the axial compressive responses of the circular HSCFST columns after exposure to constant high temperatures were investigated by experimental and numerical methodologies. A total of 7 stub HSCFST columns were exposed to elevated temperatures, and the axial compression tests were conducted after cooling. The attained temperatures, failure modes, load-deformation curves, and load-stress curves were discussed. The results of the experiments reveal a more pronounced decrease in the ultimate capacity of HSCFST columns exposed to 800 °C compared with normal-strength concrete-filled steel tubular (NSCFST) columns. A coupled thermal-stress finite element model was established and utilized to conduct parametric studies. On the basis of the 825 simulated data, design equations were suggested to evaluate the residual cross-sectional capacity of the HSCFST column.