Deformation and internal force of multitower suspension bridges: Numerical modeling and analytical analysis

An analytical model for predicting the deformation and internal forces of multitower suspension bridges is proposed in this paper. Equilibrium differential equations and deformation coordination equations are established based on deflection theory and coupling analysis of bridge components, in which the vertical stiffness contribution of girders and the longitudinal stiffness of all towers are considered. The equations for the deformation and internal forces of the bridge components, including towers, hangers, cables, and girders, are derived taking into account the live loads to which the multitower suspension bridge is subjected. The equations capture the mechanical characteristics of the bridge components, and the results can be obtained explicitly with the proposed model, notably improving the calculation efficiency. The applicability and efficiency of the proposed model are verified by two finite element model examples featuring two and three towers. A parametric analysis is performed to investigate the impact of major bridge parameters using the proposed model. The analysis results indicate that the longitudinal stiffness ratio of the mid-tower to the main cable plays an important role in the key design indices, including girder deflection and safety factor of anti-slipping of the saddle. A suitable stiffness range for the mid-tower is obtained by the proposed model.