Effectiveness of Using Elastomeric Pads to Mitigate Impact Vibration at an Urban Turnout Crossing

Summary

A turnout is a structural track system used to divert a train to other directions or other tracks. A turnout system includes rails, switches, crossings (special track components), steel plates, rubber pads, biscuits, fasteners, screw spikes, concrete bearers, ballast and formation. The wheel rail contact over the crossing transfer zone has a dip-like shape where the wheel trajectory is not smooth. The wheel/rail interaction with such imperfect contact transfer can cause detrimental impact loads on the railway track and its components. In addition, the large impact emits disturbing noises (either impact or ground-borne noise) to railway neighbors.

A methodology to reduce the wheel/rail impact at a turnout crossing is to adopt more resilient elastomeric pads. The functions of the turnout rubber pads are quite similar to those of plain-track rail pads. Nonetheless, it is important to note that the stiffness of a turnout structure is considerably higher than that of a plain track. As a result, it is desirable that the turnout pads should be softer than general rail pads, in order to moderate global track stiffness as well as to attenuate a higher impact force due to the wheel/rail interaction over the crossing transfer zone (dip-like trajectory). A trial of such methodology has been implemented at an urban turnout diamond in RailCorp’s urban rail network and the effectiveness of such a method has then been evaluated using integrated numerical train/track simulations, axle box acceleration and ride quality data obtained from the calibrated track inspection vehicle “AK Car”. The field trial demonstrates that using more resilient elastomeric pads in an urban turnout is effective in mitigating impact vibration and upgrading passenger ride comfort. However, it is important to note that an overly soft or hard pad is not recommended because it tends to reduce lives of other adjacent track components.