Dynamic performance of existing high-speed railway bridges under resonant conditions retrofitted with fluid viscous dampers

This paper deals with the application of Passive Control techniques to mitigate the excessive vibrations that short simply supported railway bridges may undergo under the circulation of High-Speed trains. A possible solution to reduce inadmissible levels of deck vertical acceleration, based on retrofitting the bridge with fluid viscous dampers connected to the slab and to an auxiliary structure, is proposed and evaluated. To this end, two real bridges belonging to the Spanish railway network are analysed using an orthotropic plate Finite Element model, which properties are updated from experimental tests performed on the structures in the past. A possible conditioning of the respective lines for higher design velocities than the current ones is considered, leading to inadmissible performances of the bridges. A particular retrofit is proposed for each structure in order to accomplish the Serviceability Limit State of vertical acceleration, and the controlling effect of the proposed system is shown for a wide range of trains and circulating velocities. In order to realistically assess the technical feasibility of the alternative, special attention is given to practical aspects related to the auxiliary structure and dampers installation.