Dynamical identification and modelling of steel-concrete composite high-speed railway bridges

In the last few years, the construction of new high-speed (HS) railways across Europe, as well as in many other countries, has required many different bridges and viaducts. Together with classical concrete solutions, new steel-concrete composite typologies have been developed, giving light and cheap structures. Despite these studies and applications, some concerns still remain about the definition of reliable models for the evaluation of their actual dynamical behaviour under HS train passage. In particular, the influence of many structural and non-structural components, such as cross-girders and ballast, are still not well recognised. In this paper, open problems related to the dynamical assessment and modelling of new steel-concrete four-parallel-girder and box-girder solutions are exposed and analysed. A suitable procedure, based on operational modal analysis, model updating and train-bridge interaction analysis is applied to two bridges, recently built in the new Italian HS network, in order to assess and verify their dynamic behaviour under operative conditions.