In-plane nonlinear buckling analysis and design method of concrete-filled steel tubular catenary arches

The prevalence of concrete-filled steel tubular (CFST) catenary arches, renowned for the optimal load-bearing efficiency, has shown a marked increase over the past decades. To date, extensive research has been conducted into the nonlinear buckling behaviors and elastic-plastic strength of circular and parabolic CFST arches, grounded on the assumption that the curvature of the arch axis remains a specific constant. However, for CFST catenary arches, this assumption is not appropriate, given the substantial variation in curvature along the arch rib, and the influence of the arch axis is not adequately addressed in the existing design codes. Therefore, in this paper, a more precise strain expression is employed to conduct the nonlinear buckling analysis on CFST catenary arches. The analytic solutions for both symmetric snap-through buckling and anti-symmetric bifurcation buckling loads are obtained. In addition, a validated finite element (FE) model is adopted to investigate the influence of key parameters, including the slenderness ratio, the arch-axis coefficient, the rise-to-span ratio, and the steel ratio, on the in-plane stability bearing capacity of CFST catenary arches subjected to axial compression. Moreover, the obtained numerical results are utilized for comparison with the prediction results calculated by the existing design codes for CFST or steel arches. The comparison results indicate that the existing design codes have tended to overestimate the in-plane strength of CFST catenary arches, mainly due to the ignorance of the influence of pre-buckling deformation. Thus, based on the nonlinear buckling analysis results, a revised lower-bound design formula for predicting the in-plane stability bearing capacity of CFST catenary arches under axial compression is proposed, considering the influence of the rise-to-span ratio and the steel ratio.