Keywords: vehicle-bridge interaction, fatigue assesment, railway bridge, steel viaduct, contact forces, moving loads.

The FADLESS research project aims at defining innovative technical guidelines for the assessment and control of existing and new bridges with regard to fatigue phenomena induced by vibrations and distortions produced by the passage of trains. For this purpose an improved representation of the vehicle loads is required.

The dynamic interaction between a bridge and the moving vehicles represents a special discipline within the structural dynamics field. In order to simulate the train-bridge interactive dynamics many kinds of two-dimensional and three-dimensional models for train carriages have been presented and adopted, in which the springs and the dashpots are used to describe the interactive effects between wheels and primary suspensions as well as primary and secondary suspensions. The subsystems interact through the contact forces, the forces induced at the contact points between the wheels and the rails surface (of the railway bridge) or the pavement surface (of the highway bridge). Such a problem is nonlinear and time-dependent because of the fact that the contact forces may move from time to time, while their magnitudes do not remain constant, as a result of the relative movement of the two subsystems.

This paper presents the results concerning the dynamic interaction between trains and the Lagoscuro bridge. In the vehicle-bridge interaction (VBI) models [1] the car bodies, the bogies and the wheels are assumed to be rigid and connected by means of springs and dashpots to represent the two suspensions systems.

Dynamic analyses will be conducted using a suitable numerical model of the Lagoscuro railway bridge. First, dynamic analyses of the bridge will be performed using the standard procedure given by the Eurocode 1, where the vehicle-bridge interaction is neglected and only a sequence of moving loads is defined, and the results will be compared with those obtained using the two-dimensional VBI model. Then, vehicle-bridge interactive analyses are performed, considering a three dimensional model for cars and bridge to study also lateral and torsional vibrations of the bridge. Data regarding the suspension systems of the high-speed train ETR500Y given in [2] are used. Finally, parametric investigations have been conducted as regard the travelling speed and the weight of the train.

1

K. Liu, G. De Roeck, G. Lombaert, "The effect of dynamic train-bridge interaction on the bridge response during a train passage", Journal of Sound and Vibration, 325, 2009. doi:10.1016/j.jsv.2009.03.021

2

K. Liu, E. Reynders, G. De Roeck, G. Lombaert, "Experimental and numerical analysis of a composite bridge for high-speed trains", Journal of Sound and Vibration, 320, 2009. doi:10.1016/j.jsv.2008.07.010

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