Dynamic train-track interactions over railway track stiffness transition zones using baseplate fastening systems

In railway industry, significant attention has been spent to solve stiffness transition zone problems since the railway tracks at these zones, especially at the transition between bridge and embankment, are prone to the significant degradation and they need extra maintenance activities and cost to ensure the safety and comfort of passengers. A variety of applications to solve the transition zone problems have been widely investigated. However, never has the application of baseplate fastening systems to fix the transition zone problem been fully investigated. The study proposed herein is the world's first investigation to fill the knowledge gap by using numerical models to investigate the effect of baseplate pad stiffness and baseplate weight on the dynamic behaviours of the transition zone between slab track and ballasted track. The numerical models have been simulated using LS-DYNA software and validated by comparing with field measurements and other simulation results. The obtained results present that soft baseplate pads can intensify the rail displacements and increase an uneven track profile at transition zone. The results also show that the effect of baseplate weight play a slight role in reducing the differential settlement. The 400 MN/m/m(2) pad stiffness provides the best solution as the slab track stiffness can be equalised to the stiffness of ballasted track. Overall, the optimal stiffness of baseplate can significantly reduce the differential settlement leading to reduce track degradation. However, the uses of heavier baseplates and softer baseplate pads together may cause negative effect by increasing the rail displacements leading to higher differential settlements. Hence, baseplate fastening systems should be carefully selected to maximise the benefit of baseplate fastening systems. The new insights will help track engineers to make an appropriate decision on the design and usage of baseplate fastening systems at the stiffness transition zone to mitigate the risk of accelerated track degradation.