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Highlights: [•] A retrofit solution to mitigate excessive vibrations in railway bridges is proposed. [•] The retrofit is based in a double beam system linked with fluid viscous dampers. [•] Partial clamping of the secondary beam supports improves the system performance. [•] High transverse acceleration levels at platform can be reduced with the alternative. [•] Secondary beam size may be drastically reduce with the embedment of the supports. [Copyright &y& Elsevier]

Abstract: In this paper, the dynamic performance of a certain kind of existing bridge under the action of high-speed railway traffic is addressed. Short-to-medium-span simply supported structures are susceptible to experiencing harmful transverse vibrations under resonant conditions, leading to excessive levels of vertical acceleration, the subsequent premature deconsolidation and degradation of the ballast layer, passenger discomfort and high maintenance costs of the corresponding lines. This dynamic problem, which can require the reduction of the design velocity or the temporary interruption of the railway service to undertake corrective actions, has been reported in Europe, China and Japan during the last decades (European Rail Research Institute (2000) , Duan (1995) , Ishibashi (2004) ). In particular, single-track simply supported short bridges appear to be quite critical structures in this regard. In what follows, the authors present an evaluation of the dynamic performance of three real bridges on the Spanish railway network, located in double-track branches but composed of structurally independent decks. The objective of the investigation is to compare their performance with that of hypothetical modified double-track versions of the original decks. An orthotropic plate finite element model, whose properties are updated from experimental tests performed on the bridges in the past, is used to predict the structural dynamic responses in the time domain. Finally, the predominant effect of the increase in the mass of the bridges over the increase in the eccentricity of the tracks, the reduction in the natural frequency experienced by the torsion mode, and the relevance of three-dimensional modal contributions is proven, leading to remarkable reductions of the maximum acceleration levels in the multiple-track modified structures. [Copyright &y& Elsevier]

Abstract: 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. [Copyright &y& Elsevier]