Suspension bridge deformation and internal forces under the concentrated live load: Analytical algorithm

Abstract

Suspension bridge is a flexible structure, which responses to live loads are quite complicated due to the coupling of several factors. In this paper, an analytical algorithm is proposed for estimating the deformation and internal forces of earth-anchored suspension bridges under the concentrated live load. Based on the known parameters of the completed bridge and the live load, the deformation of the main cable, the deformation of the girder, the relationship between the main cable and the girder, and the deformation of towers are successively analyzed. Next, four categories of governing equations are set up, namely, the conservation of the unstrained length of each main cable segment, the force and deformation coordination of each hanger, the closure of length and elevation difference in each span, and the mechanical balance of the girder. The total number of governing equations is equal to that of basic unknown parameters. Finally, all the governing equations are incorporated into an objective function, and the programming solution is carried out. The values of the basic unknown parameters are determined so that all the governing equations hold true simultaneously. Based on this, all other parameters are derived and the deformed state of the structure is expressed. The proposed method's feasibility and effectiveness are verified by its application to an earth-anchored suspension bridge with a main span of 1080 m. Both the deformation and internal forces under the live load are accurately estimated using the proposed analytical algorithm, which agree well with the finite element analysis.