Monitoring of strain of in-service railway switch rails through field experimentation

In the financial year 2009/10, the Great Britain (GB) rail infrastructure manager, Network Rail, spent 32 pound million on the failures within switches and crossings. Approximately 53% of those failures occurred within the switch panel. In addition, two major incidents in GB in recent years have highlighted a lack of understanding of the loads and vibrations experienced by, and the consequent rates of deterioration of, switch panels. This paper describes work which has been undertaken to help improve understanding of in-service loads experienced by switch panels and their consequent deterioration rate. Field experimentation has been designed and installed on four sites around GB, with the same design of switch. The change in response to loading, and the rate of deterioration, of the switch panels at each site was monitored over time. The effect of the vehicles and the deterioration were analysed individually before a comparison between the four sites. The analysis from the strain gauge measurements showed that there was an increase in the variance and maximum strains generated on the stock rail with the switch closed compared to when the switch is open. Finite element analysis was used to validate variation recorded by the strain gauges under similar loads.