Analysis Of The Influence Of The Ballast Track In The Dynamic Behaviour Of Single-Track Railway Bridges Of Different Typologies

[EN] Short-to-medium span simply-supported (SS) railway bridges are prone to experience high levels of vertical acceleration due to train passage. The necessity of predicting accurately their dynamic behaviour for design, safety and maintenance reasons, requires a deep understanding of the train induced vibrations in these structures. A key factor of this phenomenon is the influence exerted by the ballast track on their dynamic response. This paper provides a detailed sensitivity analysis over a single-track bridge catalogue covering lengths of interest from 10 to 25 m considering two different typologies, (i) girder-deck bridges and (ii) slab-deck bridges. The effect of the vertical flexibility of elastic bearings is also analysed. A 2D Finite-Element (FE) track-bridge interaction model is implemented with the aim to evaluate the influence of the track parameters on the modal properties of the bridges and the dynamic response under train passages. The results obtained reveal the influence of the ballast shear stiffness and damping in the dynamic behaviour of the structures, especially in the case of the shortest girder bridges.