USPs on damage reduction of concrete railway sleepers

Abstract

Ballast is the weakest among all of the railway track components due to its latent dynamic shifting and variation of stiffness along and across the track. Sharp Angular shape of the ballast components hinders evenly distribution of loads from sleeper to ballast, which in turn causes the sleepers to deteriorate over time resulting in higher frequency of railway track maintenance. Previous studies have shown that having an under-sleeper pad (USP) in between sleeper and ballast increases the contact area between them significantly. This by itself reduces the long-term damage on sleepers by a substantial amount. However, concrete sleeper is subjected to cracking due to excessive dynamic load from rail wheels. This paper intends to numerically evaluate whether the cracking of concrete sleepers gets reduced due to installing of USPs in the railway track system. The foremost reason behind cracking of concrete sleepers is the induced dynamic loads due to track irregularities and imperfect wheel rail contact. The most affected portion is at the bottom of the rail seat location of sleeper. Thus, two finite element models (one without USP and one with a 20mm thick USP attached at sleeper bottom) were analyzed while incorporating the concrete damage plasticity in the sleepers’ material. Results have shown better performance of concrete sleepers with USPs. Sleeper pads have shown a tendency to minimize excessive stress developed within naked concrete sleepers. Substantial advantage of using USPs in terms of damage reduction among sleepers were also perceived during conducting this analysis. Consequential reduction of crack formation was observed after installation of USPs.