Eccentric compression behaviour of normal and ultra-high performance concrete-filled stainless steel tube stub columns

To investigate the mechanical properties of normal concrete -filled stainless steel tubes (CFSST) and ultra -high performance concrete -filled stainless steel tubes (UFSST) under eccentric compression, 6 axial compression specimens and 18 eccentric compression specimens were designed. The effect of different concrete strengths, eccentricity and diameter -to -thickness ratios ( D/t ) on the damage modes, load -displacement curves, load -strain curves, and lateral deflection distribution curves of the specimens were investigated. The test results showed that stainless steel tubes exhibited different degrees of buckling after failure. The load -displacement curve of CFSST presents a slight upward trend after the elastic -plastic phase, whereas that of the UFSST enters a slowly decreasing phase. And the increase in eccentricity leads to a decrease in the load bearing capacity, ductility, and initial stiffness of the specimen. As the D/t decreases, the load carrying capacity of the specimen increases. Additionally, parametric analysis was conducted on CFSST and UFSST specimens, including the eccentricity, concrete strength, stainless steel yield strength, and D / t . Compared with the design codes of EC 4, AISC 360, and GB/T 51446, the ultimate axial force -bending moment ( N u - M u ) curve was inaccurate. Thus, a prediction model for the N u - M u curve of CFSST and UFSST stub columns was proposed, and the predicted results of the proposed model were in good agreement with the experimental results.