Keywords: bridge dynamics, high-speed trains, resonance phenomena, moving loads, fluid-viscous dampers, passive control, orthotropic plates.

The dynamic performance of railway bridges is an increasingly relevant issue in public transport systems due to the extensive construction of new high-speed railway lines and the use of old lines for higher operating train velocities. Higher design velocities may lead to resonant phenomena, entailing adverse consequences such as ballast destabilization, risk of derailment, deterioration of passenger comfort and a rise in the maintenance costs, especially in short simply supported structures [1].

In order to mitigate the excessive vertical oscillations experienced by bridge decks, a specific type of retrofit has already been proposed by the authors [2,3]. It consists on artificially increasing the overall damping, retrofitting the deck with fluid viscous dampers linking the vertical motion of the slab with that of an auxiliary structure. This solution could substitute a classical strengthening process in existing railway bridges, being one of its principal advantages the possibility of installation and maintenance without interfering with everyday railway traffic. In order to realistically assess the technical feasibility of the proposed alternative, some practical aspects related to the damper installation are now analyzed, such as (i) the effect of the local deformation of the slab at the damper connections and, (ii) the forces transmitted by these elements to the bridge and auxiliary structure.

A finite element code has been implemented specifically to predict the retrofitted structure response under railway traffic. As a result of the usual topologies of short simply supported bridges the bridge deck is modeled as an orthotropic thin plate simply supported on elastic bearings. The influence of the bearing vertical stiffness on the bridge dynamic response and the need of simulating these elements in order to adequately predict the structural response are evaluated as well. Finally, a real bridge belonging to the Spanish railway network is analyzed. A particular retrofit is proposed for the structure and the dynamic response of the original and retrofitted cases are compared. The controlling effect of the retrofitting system is proven for a wide range of trains and circulating velocities.

1

L. Frýba, "Dynamic behaviour of bridges due to high-speed trains", R. Delgado, R. Calçada, A. Campos e Matos, eds., Workshop Bridges for High-Speed railways, Porto, Portugal, June 3-4, 2004.

2

P. Museros, M.D. Martínez-Rodrigo, "Vibration of simply supported beams under moving loads using fluid viscous dampers", Journal of Sound and Vibration, 300, 292-315, 2007. doi:10.1016/j.jsv.2006.08.007

3

M.D. Martínez-Rodrigo, "Atenuación de vibraciones resonantes en puentes de ferrocarril de Alta Velocidad mediante amortiguadores fluido-viscosos", PhD Thesis, Universidad Politécnica de Valencia, 2009.

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