Modelling scheme for railway vehicle/track/ground dynamic interaction in the time domain

Modelling of vehicle/track/ground dynamic interaction is an important issue for railway design. Better
understanding of how the moving dynamic loads are distributed through the track components to the ground can
be derived from these numerical results to improve the stability of the moving train and decrease the cost of the
maintenance. Nonlinear models of the ground may be required due to the large displacements induced by
heavier and/or high-speed trains. The aim of this research is to develop a general modelling approach for
predicting the dynamic behaviour for a variety of situations.
A three-dimensional vehicle/track/ground approach in the time domain is presented. The finite element method
is used to model the track/ground vibration. The equations of motion of a multi-body vehicle are implemented to
couple with the ground/track system. An alternative approach to the commonly used infinite elements is
proposed for modelling the far-field, based on the use of mass-proportional damping to suppress the reflections
from model edges. Improved results are shown and better efficiency can be found compared to the results from
models with infinite elements. Furthermore, two different geometries for the ground model, a hemispherical and
a cuboid one, are discussed. The issue of transients developed by the moving load is discussed and it is shown
that long models are required for load speeds close to the wavespeed in the ground to allow the results to
achieve steady state. Finally, the results are benchmarked against the results from a wavenumber FE/BE model.