Sensitivity of rail pads on dynamic responses of spot replacement sleepers interspersed in ballasted railway tracks

In many countries, timber sleepers have been widely used in railway networks. Over the time, timbers degrade and it becomes more difficult to seek cost-effective hardwood sleepers to re-place the deteriorated timber sleepers. To enable a short-term solution, many infrastructure managers adopt the interspersing method of track maintenance. The interspersed pattern sleeper, a spot replacement of old timber sleeper with concrete or composite counterparts, of railway track is often used as a temporary maintenance for secondary railway lines such as yards, bal-loon loops or siding. It is observed that performance of interspersed tracks can quickly deterio-rate after some years due to impact loading condition induced by track stiffness difference. On this ground, a nonlinear simulation of interspersed sleeper railway is conducted using the finite element program, STRAND7, so that the dynamic analysis can be conducted. Two moving point loads representing an axle load along each rail has been established to investigate the worst-case, potential actions for premature damage of sleepers and differential settlement of the track. In this study, the emphasis is placed on the effect of rail pad properties on the dynamic displacement and acceleration of concrete sleepers. The median train speed of 60 km/h and a va-riety of interspersed patterns have been investigated to identify the causes of track deterioration and track differential settlement. The insight will help track engineers develop a method to con-trol vibration impacts for interspersed railway tracks using resilient rail pads in conjunction with concrete sleepers.