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Keywords: railway ground vibrations, finite-infinite element method, viscous boundary, vehicle dynamics, soil-structure interaction, wheel-rail contact, track deflection.

Summary

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 [1] is combined with the infinite element method [2]. 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.

References

1: J. Lysmer, R.L. Kuhlemeyer, "Finite dynamic model for infinite media", Journal of the Engineering Mechanics Division, Proceedings of the ASCE, 95(EM4), 859-877, 1969.
2: O.C. Zienkiewicz, C. Emson, P. Bettess, "A novel boundary infinite element", International Journal for Numerical Methods in Engineering, 19(3), 393-404, 1983. doi:10.1002/nme.1620190307

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Front Page Browse CCP CSETS CTR IJRT Other Authors Search Purchase Guide FAQ Contact us	Civil-Comp Proceedings ISSN 1759-3433 CCP: 96 PROCEEDINGS OF THE THIRTEENTH INTERNATIONAL CONFERENCE ON CIVIL, STRUCTURAL AND ENVIRONMENTAL ENGINEERING COMPUTING Edited by: B.H.V. Topping and Y. Tsompanakis Paper 7 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, Faculty of Engineering, University of Mons (UMONS), Belgium doi:10.4203/ccp.96.7 download the full-text of this paper Full Bibliographic Reference for this paper 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. Summary 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 [1] is combined with the infinite element method [2]. 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. References 1 J. Lysmer, R.L. Kuhlemeyer, "Finite dynamic model for infinite media", Journal of the Engineering Mechanics Division, Proceedings of the ASCE, 95(EM4), 859-877, 1969. 2 O.C. Zienkiewicz, C. Emson, P. Bettess, "A novel boundary infinite element", International Journal for Numerical Methods in Engineering, 19(3), 393-404, 1983. doi:10.1002/nme.1620190307 download the full-text of this paper (PDF, 2578 Kb) go to the previous paper go to the next paper return to the table of contents return to the book description purchase this book (price £130 +P&P)
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