Damage analysis of spot replacement sleepers interspersed in ballasted railway tracks

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, balloon loops or siding. However, their negative effect on the railway has not been taken into account. It is observed that performance of interspersed tracks can quickly deteriorate after some years. On this ground, a nonlinear simulation of interspersed sleeper railway is conducted using the finite element program, STRAND7, so that the structural damage 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. Dynamic displacement and acceleration of sleeper are then evaluated by varying the speed of the moving force from 5 km/h to 120 km/h and the interspersed patterns to identify the causes of track deterioration and track differential settlement. The insight strongly demonstrates the potential cases and engineering guideline for interspersed railway tracks.