During recent decades, increased damage of the crossing nose in turnouts where the wooden sleepers were replaced by the concrete ones has been observed in the Dutch railway network. It should be noted that the elastic properties of the turnout structure was not adjusted when replacing the sleepers. In [1] it was shown that by increasing the elasticity of the turnout supporting structure the dynamic forces in the crossing nose could significantly be reduced. The goal of the research presented here is to improve the turnout design by tuning the elastic properties of the track structure with the aim to reduce the dynamic forces in the crossing nose.

The train and turnout interaction has been investigated in a number of research papers being published recently [2,3,4,5,6,7]. Here the dynamic interaction between the railway vehicle and track structure has been analysed in time domain using the two-dimensional finite element model (DARTS_NL). A procedure for obtaining vertical rail geometry in crossing using visual images suggested in [1] has been used here.

Using DARTS_NL a turnout 1:9 on a ballast bed with and without under sleeper pads (USP) has been modelled. Performance of the turnout has been improved using a numerical optimisation method. The stiffness and damping of the elastic elements of the crossing track structure such as rail pads and USP have been chosen as the design variables. The combined objective function is a weighted sum of the dynamic forces on rails, sleepers and ballast, which should be minimised. Constraints are imposed on the displacements and stresses of the structural elements. The results of the optimisations have shown that the stiffness of the elastic elements should be reduced in order to reduce the dynamic forces. The results have also revealed that for the best turnout performance the stiffness of the elastic elements should not be the same along the crossing.

1

V.L. Markine, M.J.M.M. Steenbergen, I.Y. Shevtsov, "Combatting RCF on switch points by tuning elastic track properties", Wear, 271, 158-167, 2011. doi:10.1016/j.wear.2010.10.031

2

A. Johansson, B. Palsson, M. Ekh, J.C.O. Nielsen, M.K.A. Ander, J. Brouzoulis, E. Kassa, "Simulation of wheel-rail contact and damage in switches & crossings", Wear, 2010. doi:10.1016/j.wear.2010.10.014

3

E. Kassa, C. Andersson, J.C.O. Nielsen, "Simulation of dynamic interaction between train and railway turnout", Vehicle System Dynamics, 44(3), 247-258, March 2006. doi:10.1080/00423110500233487

4

M. Wiest, W. Daves, F.D. Fischer, H. Ossberger, "Deformation and damage of a crossing nose due to wheels passages", Wear, 265, 1431-1438, 2008. doi:10.1016/j.wear.2008.01.033

5

C. Andersson, T. Dahlberg, "Load impacts at railway turnout crossing", Vehicle System Dynamics, 33(SUPPL), 131-142, 2000.

6

A. Johansson, J.C.O. Nielsen, R. Bolmsvik, A. Karlström, "Under sleeper pads - Influence on dynamic train-track interaction", Wear, 265, 1479-1487, 2008. doi:10.1016/j.wear.2008.02.032

7

S. Alfi, S. Bruni, "Mathematical modelling of train-turnout interaction", Vehicle System Dynamics, 47(5), 551-574, 2009. doi:10.1080/00423110802245015

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