Static characteristics analysis of three-tower suspension bridges with central buckle using a simplified model

Compared with traditional two-tower suspension bridges, three-tower suspension bridges have to face challenges caused by the mid-tower effect, which requires the stiffness of the mid-tower satisfying two contradictory parameters, the deflection-to-span and the saddle sliding resistance coefficient, simultaneously. Meanwhile, the central buckles are often utilized to reduce the live load deflection and the torsional vibration caused by wind in two-tower suspension bridges. This study proposes an analytical model for predicting the structural responses of three-tower suspension bridges with central buckle under vehicle loads and examines the effect of the central buckle on suppressing the mid-tower effect. The analytical model simplifies the bridge as a series of cables with horizontal spring constraints. The validation analysis based on the structural parameters of the Yingwuzhou Yangtze River Bridge using the nonlinear finite element method demonstrates that the error of the proposed model does not exceed 5%. The parametric investigations show that the central buckle can significantly improve the performance of three-tower suspension bridges by enhancing their stiffness and reducing the unbalanced tension of the main cable on both sides of the mid-tower. Three-tower suspension bridge with central buckle has a much wider feasible mid-tower stiffness range than that of the traditional three-tower suspension bridges, and the critical dead-to-live load ratio for the feasible dimensionless stiffness range has decreased from 6.7 to 4.4.