Out-of-plane stability of concrete-filled steel tubular arches at elevated temperatures

Abstract

This paper investigates the flexural-torsional buckling behaviour of concrete-filled steel tubular circular arches under mechanical and thermal loading. A thermo-elastic pre-buckling analysis is first conducted by employing the principle of virtual work to derive the non-linear equations of equilibrium. The governing geometrical, equilibrium and constitutive material relations are numerically solved as a system of first-order differential equations with boundary conditions of pinned or fixed ends. The prebuckling analysis is then generalised to consider basic creep strain which is found to have a negligible impact on the prebuckling response under short-term heating. Subsequently, an elastic out-of-plane buckling analysis is performed using energy methods and the influence of thermal loading on buckling loads is examined. The results show that stability boundaries decrease with an increase in thermal loading, and that the rate of reduction is independent of the type of end-supports. Additionally, a Finite Element (FE) model is developed to analyse the inelastic lateral buckling strength of CFST arches under both uniform thermal and fire loading. The FE analysis is validated by comparison to the numerical method derived herein for the elastic buckling analysis.