Keywords: high speed rail, dynamic interaction of coupled media, interface coupling, soil-track-train interaction, finite element method, boundary element method.

High speed rail (HSR) systems represent a popular transportation mode worldwide. Effective designs are based on a good understanding of the behavior of the coupled in nature transient soil-track-train system for HSRs. In-situ measurements, experimental testing, analytical and computational techniques and computer simulations provide such an insight. In-situ measurements and experimental testing programs are associated with high costs and high risks since they require either existing systems or large scale testing facilities. Analytical techniques and computer simulations are very cost-effective means of exploring the behavior of complex systems through parametric investigations. The physical system under consideration consists of three distinct components: (i) The propagation of the wave in the semi-infinite layered soil region and the embankment; (ii) The deformable rail and track structure; and (iii) The train vehicle that moves at high speeds. Accurate mathematical models of the physical problem should sufficiently represent the behavior of each of the components of the physical system and consider the dynamic interaction among the three components. The finite element method (FEM) and the boundary element method (BEM) are among the popular techniques used for the solution of the models each component. The present work introduces an explicit coupling scheme of multiple solvers by enforcing equilibrium and compatibility conditions at the interfaces [1]. The BEM within the framework of impulse response techniques is used for the solution of the wave propagation problem. The FEM is used for the rail and track and to model the vehicle dynamics. Each method uses independent time steps to satisfy accuracy and convergence conditions. The solutions are coupled at the interfaces using the proposed method. The method development and implementation are discussed. The applicability and accuracy of the coupling approach has been investigated and an example has been presented. Based on these results it is concluded that: (1) The proposed approach yields highly accurate responses for coupled systems when compared to exact solutions of the full models and other rigorous analysis solutions; (2) The approach has the flexibility to be extended to multiple interface connections using both the FEM and the BEM solutions; (3) System models can be condensed to the interface degrees of freedom only so the solution of the coupled response is not only accurate but highly efficient; (4) The approach allows for each system to be analyzed independently at time steps geared specifically to the frequency content of the system.

1

J. Mulliken, D.C. Rizos, J.M. Caicedo, "Non-iterative coupling of interacting systems solved by time domain FEM and BEM", Soil Dynamics and Earthquake Engineering, (under review), 2010.

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