Out-of-plane creep buckling analysis on slender concrete-filled steel tubular arches

Concrete-filled steel tubes (CFST) are becoming a popular structural solution for arch bridges because of their high compressive strength and efficiency in construction. For long span CFST arch bridges, the time-dependent behaviour of the core concrete may affect the stability of CFST arches. Despite this, only limited research has been carried out to date on their creep buckling behaviour. In this context, this study aims to investigate the influence of the prebuckling deformation induced by time effects on the out-of-plane stability of single parabolic CFST arches with fixed ends and subjected to uniformly distributed loads applied along the span by means of the finite element method using ABAQUS. The time-dependent behaviour of the concrete has been described using the Eurocode 2 model and implemented in the analysis using the integral type creep law. The nonlinear material property and the confinement effects under ultimate condition have also been taken into account and implemented in ABAQUS with UMAT subroutines. The accuracy of the proposed analysis method has been validated against the experimental results of an out-of-plane buckling test of a 1:10 scaled CFST arch reported in the literature. An extensive parametric study has been then carried out and it has been found that the ultimate capacity of the arches can be decreased by up to 18% due to the prebuckling deformation induced by time effects. Finally, designing equations are proposed based on the finite element analysis results to predict the ultimate loads of CFST arches accounting for time effects.