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PROCEEDINGS OF THE THIRTEENTH INTERNATIONAL CONFERENCE ON CIVIL, STRUCTURAL AND ENVIRONMENTAL ENGINEERING COMPUTING
Edited by: B.H.V. Topping and Y. Tsompanakis
Prediction of Environmental Vibrations Induced by Railway Traffic using a Three-Dimensional Dynamic Finite Element Analysis
G. Kouroussis1, L. Van Parys2, C. Conti1 and O. Verlinden1
1Department of Theoretical Mechanics, Dynamics and Vibrations, 2Department of Civil Engineering,
G. Kouroussis, L. Van Parys, C. Conti, O. Verlinden, "Prediction of Environmental Vibrations Induced by Railway Traffic using a Three-Dimensional Dynamic Finite Element Analysis", in B.H.V. Topping, Y. Tsompanakis, (Editors), "Proceedings of the Thirteenth International Conference on Civil, Structural and Environmental Engineering Computing", Civil-Comp Press, Stirlingshire, UK, Paper 7, 2011. doi:10.4203/ccp.96.7
Keywords: railway ground vibrations, finite-infinite element method, viscous boundary, vehicle dynamics, soil-structure interaction, wheel-rail contact, track deflection.
In railway-induced ground-borne vibrations, modelling is almost entirely carried out with the help of the boundary element method. The main reason is the ease of defining unbounded domains. This paper presents an interesting alternative to integral transformation-based methods by presenting the modelling possibilities of the finite element method. The accurate defining of the boundary appears to be the main constraint of the approach. In order to mimic the unbounded domain that soil represents, a viscous boundary  is combined with the infinite element method . In frequency analysis, rules about the domain dimension and element size exist and limit the applicability of finite element models to two-dimensional cases. The ground wave propagation is nevertheless a transient problem and the time domain formulation appears to be a natural way to model ground wave propagation. These non-reflecting boundaries are compared to classical free and fixed boundaries, for various domain sizes. It turns out that it is possible to work with reduced domain dimensions without sacrificing accuracy. That makes it possible to develop full three-dimensional models for predicting soil vibration problems. Viscous boundary conditions are also analysed to verify efficiency. Various cases of strain conditions at the interface or the transient response of infinite media are presented, emphasizing the choice of appropriate viscous damping coefficients for both analysis. In order to take all these aspects into account in the first step of the design process, a prediction model of railway ground vibrations is proposed as an extension of vehicle dynamic simulation, based on a decoupled approach: the vehicle-track model and the soil model are studied successively and separately. The vehicle-track subsystem is based on the multibody approach for the vehicle, coupled to a flexible track represented by finite elements-lumped masses. It provides the vertical forces acting on the soil surface, which will then be applied to the soil subsystem. Results for the Brussels tram are presented. Free field vibrations are analysed by comparing experimental data to numerical results related to homogeneous and layered halfspaces. Both results confirm the applicability of the proposed approach. Possibilities of the finite element method are finally illustrated through the calculation of the structural response of a building and its effect on the ground wave field.
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