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A wheel-rail contact formulation for analyzing the train-structure nonlinear interaction that takes into account the wheel and rail geometry is proposed. Most of the existing methods treat the contact forces as external forces, whereas the present formulation uses a finite element to model the behavior in the contact interface, based on Hertz's theory and Kalker's laws. The equations of motion are complemented with constraint equations that relate the displacements of the vehicle and structure, being the complete system solved directly using an optimized algorithm. The formulation is validated with experimental data from a test performed on a rolling stock plant.

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a b s t r a c tRailway tracks degrade faster at transition zones to railway bridges. In modern lines, backfills with bound and unbound granular geomaterials have been used to minimize this problem. To provide insight into the behaviour of the train-track system and to fill the gap between numerical and experimental studies, the authors carried out extensive field measurements. These were then used to validate a FEM model that considers the relevant track components, earthworks and bridge; accounts for the train-track interaction using contact elements; and is very accurate in reproducing the measurements. Results showed that the backfill design fulfils its purpose in that it provides a stiffness transition from the embankment to the bridge. The dynamic component of the train-track interaction remained low. The performance of the model makes it a very useful tool to further study the railway track at critical locations, such as transition zones.