Out-of-plane stability of fixed concrete-filled steel tubular arches under uniformly distributed loads

In recent years, concrete-filled steel tubular (CFST) arches have been widely used and the out-of-plane buckling of CFST arches has become a major concern. So far, few studies have investigated the out-of-plane behaviours of CFST arches, and no codes have given the design formula of the out-of-plane stability bearing capacity. Therefore, in this paper fixed CFST parabolic arches with a circular cross-section under uniformly distributed loads are investigated. Considering the effect of material and geometric non-linearity, the distributions of the internal forces and deformations are observed, and on this basis an equivalent column model is established to derive the out-of-plane effective length coefficient. In addition, based on the stability theory, the nominalised slenderness ratio of CFST arches is modified considering the influence of rise-to-span ratios and can be substituted into any available stability coefficient equations in current design codes to calculate the out-of-plane bearing capacity of CFST parabolic arches. The proposed equation – which has a form of formula similar to the available stability equations in existing designing codes for CFST or steel members and which has an accuracy equal to or greater than the equations in the available literature – would be easier for the designers to accept and use.