Numerical modelling and design recommendation of axially-loaded thin-walled RCFST slender column

The round-ended concrete-filled steel tube (RCFST) column behaves favorable prospects in engineering application due to its advantages of aesthetical properties and structural efficiency. Nevertheless, relevant studies were commonly focused on the mechanical performance of RCFST stub column. This paper developed a numerical analysis method for predicting the structural behaviour and failure mechanism of thin-walled RCFST slender column under axial compression. The nonlinear finite element (FE) modelling was established on the basis of the equivalent constitutive model and was verified well by the existing experimental results. Following this, several crucial geometric and material parameters were designed to explore the influences on the strength, stiffness and ductility of axially loaded thin-walled RCFST slender column. The impacts of various parameters on second order effect and buckling reduction factor of RCFST slender column were also identified. Furthermore, the mechanical performance of thin-walled RCFST slender column was evaluated by means of the axial force versus mid-height deflection characteristic and the contact stress. The numerical analysis results indicated that the axial strength of thin-walled RCFST slender column was obviously heightened by increasing the strength of concrete and steel in addition to the cross-section area, while contrary results were discovered with the increase of the slenderness ratio and the diameter-to-thickness ratio. Lastly, design recommendations for the axially-loaded thin-walled RCFST slender column were presented by comparing the numerical and previous experimental data with design provisions in specifications EC4, ANSI/AISI 360-16 and GB 50936.