A Parametric Study on the Dynamic Behavior of Combined Cable-Stayed and Suspension Bridges under Moving Loads

A parametric study to investigate dynamic behavior of long-span combined cable bridges under moving loads is proposed. The bridge typology is based on the combination of both cable-stayed and suspension systems. The theoretical formulation is based on a continuum approach, which has been utilized in the literature to analyze long-span bridges. The bridge formulation is developed for combined stayed-suspension cable schemes, which can be easily specialized to analyze perfect cable-stayed and suspension bridges. In order to investigate the dynamic response of cable-supported bridges under moving loads, comparisons in terms of main deformability and stress-bridge parameters are proposed. Dynamic equilibrium equations lead to a partial differential problem, which has been solved, numerically, by means of a finite difference scheme. The formulation is developed in a dimensionless context by means of proper variables strictly connected with moving loads and bridge properties. In order to quantify the amplification effects produced by the moving system on typical design bridge variables, a comparative study involving the behavior of cable-stayed, suspension, and combined cable system configurations is developed. The optimal ratios of cable steel quantity involved in both cable-stayed and suspension systems are discussed, providing specific rules that guarantee smaller material amounts in the cable systems and an improved structural behavior of the combined bridge scheme.