Stability Analysis of Special-Shape Arch Bridge

This paper presents a stability investigation of a special-shape arch bridge with a span of 180 m. Its structure and mechanics are significantly different from normal arch bridges because of its single arch rib skewing across the girder, its hangers hanging unevenly along the arch rib with different aslant angle, and its arch rib being subjected to massive axial compression force, bending moment, torque, and shear stress. In this paper, the eigenvalue method is used to analyze some of the main influencing factors, such as different loads, restraint conditions of arch spring, stiffness of arch rib, stiffness of main girder and rise-span ratio of arch rib. The study results showed that the slant hangers at both sides of the girder reduced the tendency of arch instability, which is obviously helpful to maintain overall structural stability. Increasing the height of the main girder can improve the structural stability, but the effect is limited. The restrained conditions of the arch spring markedly influence the overall structural stability, and the stability coefficient of a fixed arch is more than twice the coefficient of a two-hinge arch. The rise-span ratio has a relatively large impact on the stability coefficient. A reasonable rise-span ratio for the special-shape arch bridge studied here is around 0.37 that is larger than an expected ratio for a normal arch bridge obtained in existed studies. The impacts of vertical flexural stiffness and lateral flexural stiffness of the arch rib on the structural stability are determined by the mode of buckling, and the lateral flexural stiffness has nearly no impact on the structural stability for an in-plane buckling arch.