Experimental evaluation of railway switch and crossing (S&C) modular bearer performance

Abstract

Railway switch and crossing (S&C) are an essential part of the railway track as they enable trains to change paths. Traditionally, S&C comprises continuous long bearers, up to over 6 m in length, which help to maintain gauge and prevent lateral movement between the rails. However, to decrease the cost and time associated with maintenance works, modular S&C have been introduced. These use jointed bearers which enables pre-assembled sections of S&C to be transported to and fitted on site. The joints used to tie the bearers can vary in stiffness and their location can change. This poses some questions, as the inclusion of a joint within the bearers may affect track behaviour. This research investigated the performance implications of introducing a joint in the bearers, the relative merit of various joint types and their locations with respect to the loaded rails. It also explored mitigation options, such as the lateral confinement of the ballast shoulder. This was done using full-scale laboratory testing on a single bearer bay of track, three-point bending tests and finite element modelling. It was found that eccentric loading of bearers resulted in significant variation in permanent settlement and resilient deflections along the length of the bearers. This effect was mitigated with the lateral confinement of the ballast shoulder, which offered lateral stability to the shoulder ballast. Whilst the use of a joint between the loaded rails exacerbated the variation in permanent settlement along the length of the bearers, it drastically reduced the rate of change in resilient deflections over the course of loading cycles. Joining symmetrically loaded segments of bearers can mitigate the tilting of the bearers and reduce differential settlement along the bearer length. Results from this work will enrich current S&C models and provide insights to benefit the development of new modular bearer joints.

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ORCID for William Powrie: orcid.org/0000-0002-2271-0826

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