Laboratory measurements of dynamic properties of rail pads under incremental preload

Rail pad is an important component in ballasted railway track. Its main function is to attenuate track loads, preventing underneath railway sleepers from excessive stress waves. Generally, the dynamic track design relies on the available data that are mostly focused on the condition at a specific toe load. Recent findings show that track irregularities appreciably amplify the loads over railway tracks. This nature of traffics gives rise to a considerable concern that the rail pad undergoes higher effective pre-loading than anticipated in the past. On this ground, this paper highlights the significance of pre-loading on dynamic properties of polymeric rail pads. An innovative test rig for controlling preloads on rail pads has been developed. Based on single-degree-of-freedom impact-excitation responses, the rail pads, which have been subjected to incremental preloads, are tested for their modal parameters such as dynamic stiffness and damping constants in laboratory. The influence of large preloads on dynamic properties of the rail pads is portrayed. The further discussion also involves the approach to adopt the relationships between dynamic properties versus preloading variations in practical uses.

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