Rail steel bridges are vulnerable to high impact forces due to the passage of trains; unfortunate- ly the determination of these transient impact forces is not straightforward as these are affected by a large number of parameters, including the wagon design, the wheel-rail contact and the design parameters of the b ridge deck and track, as well as the operational parameters – wheel load and speed. To determine these im- pact forces, a detailed rail train-track/bridge dynamic interaction model has been developed, which includes a comprehensive train model using multi-body dynamics approach and a flexible track/bridge model using Eu- ler–Bernoulli beam theory. Single and multi-span bridges have been modelled to examine their dynamic char- acteristics. From the single span bridge, the train critical speed is determined; the minimum distance of two peak loadings is found to affect the train critical speed. The impact factor and the dynamic characteristics are discussed.
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