Keywords: dynamics, bridges, impact factor, resonance, vehicle-bridge interaction, lateral dynamics, wheel-rail contact, nonlinear.

The dynamic effects of high-speed trains on viaducts are important issues for the design of the structures, as well as for the consideration of safe running conditions for the trains. In this work we start by reviewing the relevance of some basic design aspects. The significance of impact factor envelopes for moving loads is considered first. Resonance which may be achieved for high-speed trains requires dynamic analysis, for which some key aspects are discussed. The relevance of performing a longitudinal distribution of axle loads, the number of modes taken in analysis, and the consideration of vehicle-structure interaction are discussed with representative examples.

The lateral dynamic effects of running trains on bridges is of importance for laterally compliant viaducts, such as some very tall structures erected in new high-speed lines. The relevance of this study is mainly for the safety of the traffic, considering both internal actions such as the hunting motion as well as external actions such as wind or earthquakes [1]. These studies require three-dimensional dynamic coupled vehicle-bridge models, and consideration of wheel to rail contact, a phenomenon which is complex and costly to model in detail. We describe here a fully nonlinear coupled model, described in absolute coordinates and incorporated into a commercial finite element framework [2]. The wheel-rail contact has been considered using a FastSim algorithm which provides a compromise between accuracy and computational cost, and captures the main nonlinear response of the contact interface. Two applications are presented, firstly to a vehicle subject to a strong wind gust traversing a bridge, showing the relevance of the nonlinear wheel-rail contact model as well as the dynamic interaction between bridge and vehicle. The second application is to a real HS viaduct with a long continuous deck and tall piers and high lateral compliance [3]. The results show the safety of the traffic as well as the importance of considering features such as track alignment irregularities.

[1]

W. Guo, H. Xia, Y. Xu, "Running safety analysis of a train on the Tsing Ma Bridge under turbulent winds", Earthquake Engineering and Engineering Vibration, 9(3), 307-318, 2010. doi:10.1007/s11803-010-0015-3

[2]

P. Antolin, J.M. Goicolea, J. Oliva, M.A. Astiz, "Nonlinear train-bridge lateral interaction using a simplified wheel-rail contact method within a finite element framework", Journal of Computational and Nonlinear Dynamics, 2012. (in press)

[3]

F. Millanes, J. Pascual, M. Ortega, "'Arroyo de las Piedras' viaduct: The first composite steel-concrete high speed railway bridge in Spain", Structural Engineering International, 17(4), 292-297, 2007. doi:10.2749/101686607782359047

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