Infuence of cracked sleepers on the global track response: Coupling of a linear track model and nonlinear finite element analyses

Abstract

In the procedure of designing a prestressed concrete sleeper to be used in a railway track, irregularities of the wheels and rails may induce substantial dynamic loads that have to be accounted for. A global track model together with a nite element model of the sleeper were used to analyse the inuence of cracks in sleepers on the response of the entire track during a train passage. A train passage was simulated with the track model, and the time history of the vertical displacement at the rail seat position of a sleeper was obtained. This time history was applied to the sleeper in the nonlinear nite element model of both the sleeper and the underlying ballast, and detailed studies of the dynamic behaviour of the sleeper were made. The studies made with sleeper and track models showed that cracks in the sleepers had a minor effect on the direct response of the entire track. However, it is important to realize that cracks in the sleepers greatly reduce their lifetime; hence such cracks are very undesirable. The studies also showed that the interaction between the sleeper and the underlying ballast can be of importance for the dynamic behaviour of the sleeper. During a train passage, the time histories of the vertical displacement for the sleeper and the ballast can involve oscillation out of phase. This results in large impact forces as the sleeper hits the ballast surface.