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Field Investigation on Dynamics of Railway Track Pre-Stressed Concrete Sleepers

A comprehensive field investigation was made with the aim of achieving a better understanding of the dynamics of railway track pre-stressed concrete sleepers. Modal analysis and free decay method were used to determine the natural frequencies, model shapes and damping of sleepers. The validity of the results is discussed by comparing the results obtained here with those available in the literature. In order to investigate the characteristics of the dynamics of the loads imposed on the sleepers, load cells were installed between the rail seat and the sleeper and beneath the sleeper, recording the interaction between both sleeper and rail, and sleeper and ballast. The loads transferred from the rail to the sleeper and from the sleeper to the ballast were measured as a function of train speed. The rail seat load and the contact pressure between the ballast and the sleepers versus train axle loads and train speeds were recorded. The effects of the sleeper supporting conditions on the sleeper dynamic behaviour were investigated. The ratios of the rail seat load and the ballast contact pressure to the wheel load were obtained from the analyses of the field test results. These ratios were used to calculate the dynamic impact factors and ballast-sleeper pressure distribution patterns required for the design of sleepers. The methods, the test procedures and the results are presented and discussed in this paper.