Influence of Soil Stiffness on the Dynamic Behaviour of Bridges Travelled by High-Speed Trains

The present paper aims to study the influence of the soil/structure interaction on the dynamic behaviour of bridges, when high-speed trains travel on them. To better understand the importance of this interaction, the paper comprises the study of two distinct bridges. . Different models with soil inclusion are created in order to study, comparatively to the model with stiff supports, the results for accelerations, displacements and section forces of the deck. The study demonstrates the aggravation in the dynamic behaviour of the bridges when soil is considered and therefore, the importance of its simulation. Accelerations in models where soil was considered are always higher than in the model with stiff supports. The upper limit of 3,5 m/s 2, proposed by the Eurocode, is overcome in some of the tested models. In addition, section forces are always more severe in these models as well. A comparison of the models' eigenvalues showed the correct consideration of soil stiffness and a dependence between the modes of vibration and the effects on the structures behaviour was verified. This article suggests a way to consider soil simulation in rail bridge design.