Dynamic Analysis of Multispan Viaducts with Weak Coupling between Adjacent Spans

This paper deals with the dynamic analysis of multispan simply supported railway viaducts subjected to moving trains. In the analysis, the Sesia viaduct is considered, which is a composite railway bridge consisting of seven isostatic spans. An experimental analysis shows that the modes of adjacent spans are connected because of the weak coupling through the ballast and rails. In this case, a model of the entire viaduct is needed for an accurate prediction of the dynamic response of the bridge during the passage of the train. To reduce the computational cost, two alternatives are investigated: a single-span model with adjusted boundary conditions and a component mode synthesis (CMS) reduced-order model comprising all seven spans. The two models are subsequently used for dynamic train-bridge interaction analysis. The predicted dynamic responses of the viaduct during a train passage with both models are in good agreement with the experimental results. Compared with the single-span model, the coupling between adjacent spans is better represented by the CMS model of the entire viaduct. In practical engineering design, however, the single-span model with adjusted boundary conditions can be used to obtain a reasonably good representation of the dynamic behavior of the bridge.