Research on the Axial Compressive Performance of CFSSSTs Under Low Temperatures

This paper conducted axial compression tests on six concrete-filled square stainless steel tube （CFSSST） columns and two hollow square stainless steel tube （HSSST） columns under different temperature conditions （ranging from -30 ℃ to 20 ℃）， to investigate the effects of low temperature and slenderness ratio on their failure modes， bearing capacity， and ductility. The results indicated that when the environmental temperature decreased to -30 ℃， the bearing capacity and initial stiffness of CFSSST columns increased significantly， while their ductility decreased. Low temperatures yielded negligible improvement in the bearing capacity of HSSST columns. As the slenderness ratio increased， the failure mode of CFSSST columns gradually shifted from being dominated by section failure to being dominated by buckling failure. The bearing capacity of CFSSST columns primarily originated from the outer stainless steel tubes， with the core concrete effectively preventing buckling failure due to inward collapse during service. When the test results were compared with domestic and international standards， Eurocode 4， AISC 360-16， and the Chinese standards were all found to yield conservative predictions for the axial bearing capacity of CFSSST columns. Finally， considering the strain hardening characteristics of stainless steel， this paper proposed a theoretical model for stainless steel tube-concrete composite columns. The computational results agreed well with the experimental data. Based on this， axial compression data for stainless steel tube-concrete columns from domestic and international sources were collected， and the theoretical model was shown to accurately predict the experimental results.