Compression behaviours of CFSTs using stainless-steel tubes at low temperatures

This paper made pilot studies on behaviours of concrete-filled stub square stainless-steel tubes (CFSSSTs) subjected to low-temperature compression. Firstly, 16 CFSSSTs were tested under low-temperature axial compression. This testing program studied the effects of testing temperature (T) and SS-tube wall thickness (t). The tests showed that local buckling, corner-region splitting fracture, and concrete crushing occurred to CFSSSTs. The compressive load-shortening curves behaved a four-stage manner, which behaved differently from those hollow stainless-steel tubes (HSSTs). Compared with the common concrete-filled steel tube columns, the CFSSSTs exhibit a higher ductility. Studies showed that reducing T improved the compression capacity (Pu) but compromised the ductility of CFSSSTs; increasing the t of HSSTs improved the compression behaviour of CFSSSTs; filling concrete to the HSSSTs significantly improved the compression behaviour of CFSSSTs. This study also developed 3D finite element models (FEM) for the CFSSSTs using the low-temperature mechanical properties of both HSSTs and concrete, which accurately predicted compression behaviours of CFSSSTs at low temperatures. Moreover, the prediction equations in different codes were also adopted to predict the low-temperature Pu of CFSSSTs. Validations showed that these code equations provided about 15% underestimations on Pu, and they were recommended to predict Pu of CFSSSTs at low temperatures.