Towards structural design optimisation of railway crossings

Licentiate thesis, 2024

Railway switches and crossings (S&C, turnouts) connect different track sections and create a robust railway network by allowing trains to change tracks. While this provides valuable flexibility to the railway network, the flexibility comes at a cost. The maintenance, production and environmental costs for one turnout are significantly higher than the corresponding costs per kilometer of plain track due to the complex wheel–rail interaction and severe loading it has to endure during its lifetime. In one of the critical parts of the turnout, the crossing panel, high dynamic wheel–rail contact forces occur each time a train passes, even in the through route. In this thesis, the dynamics of the passage through the crossing panel is simulated and the structural loading is evaluated. The aim is to improve the long-term performance of the crossing panel by reducing the magnitude of the dynamic wheel–rail contact forces, while simultaneously reducing the material use to decrease environmental footprint and life cycle cost.

To this end, an extensive simulation model of a crossing panel is developed that enables extraction of the structural loading of each component. Based on measured data from a comprehensively instrumented demonstrator turnout, it is calibrated and validated using a calibration method that is developed in the thesis. The calibration is accomplished by tuning the parameters that are related to the support conditions of the crossing, such as sleeper support stiffness and sleeper–ballast voiding. After the calibration, very good correlation between simulation and measurements is achieved. In preparation for an optimisation of the crossing panel, which utilises the calibrated model and allows for significant design changes, structural requirements are proposed. These include dynamic load scenarios established from field measurements and load limits for the components within the crossing panel. In future work, the intention is to use the calibrated model together with the structural requirements in a structural design optimisation of the crossing panel.