In-plane stability behaviours of concrete-filled steel tubular catenary arches under different loading conditions

Concrete-filled steel tubular (CFST) catenary arches, renowned for their superior loading-bearing efficiency due to the alignment of the arch axis with the thrust line, have become the predominant choice for large-span arch bridges over the past decade. However, research on CFST catenary arches remains limited, with most studies focusing on the in-plane strength of circular and parabolic arches. And the existing design methods are tailored to a narrow range of loading conditions, which raises concerns about their applicability to CFST catenary arches. Therefore, this paper addresses this gap by designing and testing six CFST catenary arches under three different loading conditions (quarter-point concentrated load, mid-span concentrated load, and five-point concentrated loads). The failure modes, load-displacement curves, cross-sectional strain and stress development, and confinement effects were compared and analysed among the loading conditions. Additionally, the finite element (FE) models using beam elements were developed and verified against the test results to conduct a parametric analysis. The influence of arch axis coefficient, slenderness ratio, rise-to-span ratio, and steel ratio on the in-plane strength of the CFST catenary arches under seven different loading conditions was discussed. Finally, by accounting for the non-uniform distribution of internal forces along the arch rib, a lower-bound design formula for the in-plane strength of CFST catenary arches under various loading conditions was proposed, and comparisons with numerical results show that the proposed method can provide conservative predictions. © 2024