In-plane buckling behavior of slender parabolic concrete-filled steel tubular arches with fixed ends

The current codes use the equivalent beam-column method to predict the in-plane strength of concrete-filled steel tubular (CFST) arches with slenderness ratio λ≤80. Yet there are nearly 20% standing CFST arch bridges with slenderness ratio exceeding the limit, which are called slender CFST arches. The finite element model for the parabolic CFST arches with fixed ends and with the slenderness ratio higher than 80 was developed using ABAQUS to investigate the in-plane buckling behavior when subjected to uniformly distributed vertical load. After verifying the reliability of the model, a parametric analysis was conducted to study the influences of slenderness ratio, rise-to-span ratio, steel ratio, concrete strength and steel strength on the strength of the arches. Based on the parametric analysis results, a design formula was proposed by modifying the existing stability coefficient equation for uniformly loaded parabolic arches with fixed ends. In conclusion, the strength of the arches is decreased significantly with the increase of slenderness ratio, but is increased linearly with the increase of rise-to-span ratio and steel ratio. The influence of the rise-to-span ratio is more pronounced for slender arches, while the influence of the steel ratio is more pronounced for arches using steel tubes with higher strengths. The results obtained by the proposed design formula are in good agreement with the finite element analysis results with mean value 1.02-1.08, standard deviation 0.039-0.051 and variable coefficient 3.74%-4.72%.