Design of railway bridges for dynamic loads due to high-speed traffic

This contribution deals with the dynamic behaviour of railway bridges for high-speed traffic and investigates the impact of changes to the structural system on the dynamic response due to crossing trains. Multi-span simply supported beams represent the most unfavourable system for high-speed trains, structurally as well as aesthetically. Therefore, alternative structural systems were analysed to find out whether the dynamic characteristics of railway bridges can be adjusted in the design stage. Because of the strong interaction between the crossing train and the bridge structure the impact of changes to the structure is very difficult to estimate a priori. The internal forces in continuous beams with lengths exceeding 30 m are generally smaller than those in single-span beams with the same cross section and the speeds at which they can be crossed are significantly higher. By adding haunches to the beams those eigenfrequencies whose eigenmodes exhibit curvatures at the supports can be increased. Shortening the end spans leads to an increase in all eigenfrequencies and hence in resonance speeds. Using the findings from this article the dynamic stability of high-speed railway bridges can be improved at the preliminary design stage.