Benefit of damping in structural concrete for railway structures and track components

There are two types of modern railway tracks including ballasted and ballastless tracks. Ballasted tracks are optimally designed for suitability to railway operations with train speed less than 250 km/h, while ballastless tracks are more suitable for tunnelling work or higher speed trains. In both types of railway track systems, concrete is often used. However, the systems requirements for this material for real world applications are particularly demanding. Statistically, impact loading conditions comprise of nearly 25% of annual track loads. Also, abrasion from curve effects of train-track interaction causes high wear and tear. For example, railway concrete sleepers have been generally used in ballasted railway track and concrete slabs have been used for ballastless tracks around the world for over 50 years. Both safetycritical track components are commonly used to redistribute wheel forces onto track structure and to assure stable track gauge for safe passages of rolling stocks. The dynamic behaviours of concrete components are commonly well known; however, its damping characteristic is often neglected. With the increased demand for heavier and faster trains, the nature of track forces applying onto each track component is no longer static or quasi-static. The ignorance of damping can no longer be persisted as pre-mature damage or failure of track components can take place at a faster rate. A single sleeper failure may not affect open, plain track operations but it can give rise to the risks of rail breaks at rail joints, welds, bridge ends, switches and crossings, curved track, etc. Such the risks can later result in detrimental train derailments. This paper will highlight the development of high-damping concrete and the benefits of damping on the vibration mitigation of railway concrete sleepers in a track system. An established and validated finite element model of sleeper has been adopted for further studies. The model has been validated by experimental results. The insight into the vibration suppression of railway sleepers will help track engineers to decide the better choice of materials for manufacturing railway concrete sleepers.