Out-of-Plane Buckling Mechanism and Enhancing Method of Stiff Skeleton Arch Bridge When Wrapping Surrounding Concrete

This study investigates the stability of skeleton-reinforced concrete arch bridges during the concrete encasement process, employing a homogeneous generalized yield functions for extreme buckling load determination in nonlinear finite element analysis. Through an analysis of the stability of a stiff skeleton arch bridge with a 600 m span during the concrete wrapping stage, this study delves into and elucidates the mechanism by which the transverse brace enhances the out-of-plane stability capacity of the skeleton arch ribs. Additionally, a method for improving stability by controlling the lateral rotation angle of arch ribs is proposed. The results indicate that the lateral deflection angle of arch ribs serves as a crucial metric for assessing the out-of-plane stability of arch bridges. Transverse braces effectively coordinate and constrain the lateral deflections of two isolated arch ribs through their bending stiffness along the tangential direction of the arch axis. Notably, transverse braces within the range of L/8 to 3L/8 make the most substantial contribution to the lateral stiffness of arch ribs. Consequently, wrapping surrounding concrete on transverse braces within the L/8 to 3L/8 range proves advantageous for enhancing the stability of a stiff skeleton arch bridge under construction. Specifically, it is recommended to pour surrounding concrete on transverse braces at L/4 before the closure of the bottom plate’s concrete ring. After the ring of bottom plate’s concrete is closed, a symmetrical pouring of surrounding concrete on transverse braces from L/4 to the arch spring and vault is proposed.