Keywords: high speed rail, train-track interaction, train models, finite element method, dynamic model coupling, finite element model coupling.

There has been interest in the United States in expanding the current rail infrastructure to accommodate high speed train (HST) transportation, but many challenges must be addressed before it is practical. Soft soils are common on the east coast, where population densities are greatest and HST transportation would be in the highest demand. The effect of a HST running at or above Rayleigh wave speeds on these soft soils could be detrimental to surrounding infrastructure and potentially dangerous to passengers. Sheng [1] observed that for trains travelling at speeds approaching the speed of waves propagating through the ground that the train vibration reached elevated levels. Furthermore, Ju [2] found that trains travelling at critical speeds generated vibrations that decayed much slower than low-velocity trains. Thus, adverse ground and vehicle vibrations must be considered when developing HST systems. Research presented in this paper focuses on developing an efficient computational tool to simulate the effects of a HST-track-ground system to aid future planning and construction of HST rail links.

This paper aims to develop detailed models of a train and rail, and to combine the models through an interactive coupling methodology to examine the relations between the two systems. The construction of finite element train and rail models is detailed. The two models interact through a dynamic coupling system, where the vibration forces from the train act upon the rail. The systems are solved for using Newmark's Beta method, and for every time step, train-rail interaction forces are coupled to simulate real-time interaction. The coupling process matches interface node displacements between the two systems by satisfying equilibrium and compatibility requirements, and corrects the displacement of non-interface nodes so the interaction of the train and rail can be modeled accurately.

An impulse force acting on the train is simulated, and the displacements of the coupled train-rail systems are shown. Also, the displacements of a single rail-train system are shown under the same forces to validate the coupling methodology. Results have been promising, and further research on coupling the finite element and boundary element systems is ongoing to develop interactive multi-system models to accurately and efficiently simulate ground and structure vibration arising from the passage of high speed trains.

1

X. Sheng, C.J.C. Jones, D.J. Thompson, "A Theoretical Model for Ground Vibration from Trains Generated by Vertical Track Irregularities", Journal of Sound and Vibration, 272, 937-965, 2004. doi:10.1016/S0022-460X(03)00782-X

2

S.H. Ju, H.T. Lin, "Analysis of Train-Induced Vibrations and Vibration Reduction Schemes Above and Below Critical Rayleigh Speeds by Finite Element Method", Soil Dynamics and Earthquake Engineering, 24, 993-1002, 2004. doi:10.1016/j.soildyn.2004.05.004

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