Effect of unsupported sleepers on rail track dynamic behaviour

Railway track behaviour with unsupported prestressed sleepers has been investigated in the literature. However, some of the important factors – such as prestressing forces, variations of the sleeper cross-section along its length, losing or recovering contact between the sleeper and the ballast layer – have been omitted. These limitations have been addressed in this research. The effects of unsupported sleepers on the dynamic behaviour of railway track have been investigated, using an improved three-dimensional numerical model of track developed here. The validity of the model is evaluated by comparing the results obtained from the model with experimental results (obtained in this research and available in the literature). The influences of the size of the gap between the sleeper and the underlying ballast, the vehicle speed and the number of unsupported sleepers on the track dynamic behaviour were investigated. The effects of the various unsupported conditions of sleepers on the rail seat load, sleeper bending moment and sleeper–ballast contact force at various train speeds were illustrated. It was shown that consideration of sleeper prestress forces, detailed geometry of the sleepers and a more realistic assumption for the sleeper–ballast contact has considerably improved the accuracy of the results obtained from theoretical models.