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Civil-Comp Proceedings
ISSN 1759-3433
CCP: 110
Edited by: J. Pombo
Paper 199

Modeling of Train-Induced Transitional Wavefields

K.N. van Dalen1 and M.J.M.M. Steenbergen2

1Section of Structural Mechanics, Chair of Dynamics of Solids and Structures, Faculty of Civil Engineering and Geosciences, Delft University of Technology, The Netherlands
2Section of Railway Engineering, Faculty of Civil Engineering and Geosciences, Delft University of Technology, The Netherlands

Full Bibliographic Reference for this paper
K.N. van Dalen, M.J.M.M. Steenbergen, "Modeling of Train-Induced Transitional Wavefields", in J. Pombo, (Editor), "Proceedings of the Third International Conference on Railway Technology: Research, Development and Maintenance", Civil-Comp Press, Stirlingshire, UK, Paper 199, 2016. doi:10.4203/ccp.110.199
Keywords: stiffness variation, transitional/free wavefield, eigenfield, transition radiation, directivity of energy flux, railroad degradation.

Transitions in constitutive or cross-sectional properties are at the basis of long-term degradation of railway tracks. Therefore, the study of transitional wavefields excited by moving loads is of paramount importance. The study, reported in this paper, proposes an elementary model of two elastic layers, having a thin plate mounted on top, resting on a rigid foundation and connected at a straight vertical interface. The system is excited by a surface load (i.e., axle load) that crosses the vertical interface, and thus moves from one medium with given material parameters to another. Using a semi-analytical solution, the energy flux associated with the transitional wavefield (i.e., the free-field energy flux) close to the vertical interface can be assessed. Initial results show that the flux becomes powerful for load velocities close to the critical velocity or for large contrasts in the material parameters. In addition, the free-field energy flux exhibits peculiar angle dependence; depending on the load velocity and the mentioned contrast, it can be extreme in the horizontal direction, into the layers, or along the vertical interface. Though this study models transitions in a simplified way, it clearly highlights fundamental features of transitional wavefields that should be incorporated in the assessment of track degradation.

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