Railway bridges on highspeed lines — dynamic effects at subgrade to bridge transition

The approach to the railway bridges are critical zones where very important dynamic amplifications can be registered due to the sudden changes of stiffness from the subgrade to the bridge. Such phenomena are investigated considering different forms of track placement, taking as base the Riada bridge, located on the Linha do Norte of the CP (The Portuguese Railway Company). The adopted model allows for the consideration of the stiffness characteristics of the subgrade and of the bridge, including a detailed description of the structural elements of the track. The studies are carried out numerically using a dynamic analysis model which considers the interaction between train and bridge.