Fire resistance design of restrained stainless-clad bimetallic steel columns under axial compression

This paper presents a comprehensive investigation into the fire performance of axially restrained stainless-clad bimetallic steel (SCBS) columns. Based on the fire tests of five SCBS columns, finite element models were developed using ABAQUS. Thermo–mechanical analysis was conducted to obtain the variations of surface temperature, structural displacement and axial load with time, as well as key parameters such as buckling and failure temperatures. The numerical results were validated against experimental results. Based on the validated models, a comprehensive parametric study was performed to evaluate the effects of cross-sectional dimensions, initial global imperfections, load ratio, axial restraint stiffness ratio, slenderness ratio and cladding ratio on the fire resistance of the SCBS columns. Four key influencing parameters (axial restraint stiffness ratio, slenderness ratio, load ratio and cladding ratio) were identified, and their coupled interactions were analysed. Furthermore, based on the stress state of restrained SCBS columns at elevated temperatures and the design framework of EN 1993–1-2, theoretical formulae for predicting the buckling temperature, incorporating the effects of load ratio, axial restraint stiffness ratio, slenderness ratio and cladding ratio, were proposed and validated against 291 numerical cases. The developed model provides an accurate and practical approach for the fire resistance design of axially restrained SCBS columns.