Sleeper spacing has been a taboo subject throughout the railway’s history. Safety concerns related to the structural integrity have been the main causes of not addressing this matter. There are no specific and clear recommendations or guidelines in relation to this matter and the distances do not go more than 0.8 m. In order to go beyond this current situation, the following research paper analyses the influence of the spacing between sleepers on the behaviour of ballasted tracks by performing a dynamic simulation with finite elements in two dimensions for different track configurations, different elements, geometries, and separations within the frame of the ODSTRACK project. The variables studied are the vertical displacements, the forces and stresses on the most important elements of the superstructure, as well as the vertical accelerations in the sleepers and the train. The values obtained from the numerical simulations were compared with the maximum permitted values according to the guidelines. To limit this distance to the most restrictive variable among those analysed, it is necessary to make important assumptions, such as the permissible values and effective support contact areas between the sleepers and the ballast. The preliminary analyses carried out shed light on a possible increment of the spacing between sleepers’ axes up to more than 0.8 m. This suggests that important savings in railways construction costs can be achieved, and they will help to develop the next stage of the ODSTRACK project.

@en

One of the most important factors influencing the track maintenance is the transitions between parts of the track with different vertical stiffness. The dynamic forces in the super-structure, i.e. from rail to ballast/slab and subgrade, including every layer under ballast/slab until natural ground, are influenced by the type of materials, layer configuration and geometry. One way to mitigate track transition problems is to have a more gradual transition with a reduced stiffness differential. The aim of this research is to reduce vertical transient stresses and displacements under track supports at track transition areas by combining different structural configurations. For this purpose, the train-track dynamic interaction in the transition zones with different vertical stiffness values is analysed using a finite element software. A high-speed train moving on a slab and ballasted track is considered travelling in both directions. The effect of different structural track designs is studied in realistic operation scenarios. The results allow concluding that the sleeper displacements and ballast stresses can be significantly reduced in the transition zones by making small changes in the track structural elements.@en