Potential for external reinforcement of insulated rail joints

This paper aims to investigate alternative ways of reducing the deterioration and failure of railway track insulated rail joints (IRJs). Joints deteriorate faster than rail initially due to the structural discontinuity present. This weakness results in both extra displacement as a consequence of applied load and the dynamic force that results as a consequence. Over time this situation worsens as the impacts and applied stresses both damage and soften the ballast and supporting subgrade under the joint. This study initially presents a static finite element model designed to simulate the mechanics of IRJs and a comparison between plain rail and a suspended insulated rail joint under various support stiffnesses. Product design options of reinforced IRJs are then chosen as input variables of the model. Results of the model are compared with field and laboratory data acquired via the Video Gauge, which is a new high-resolution optical measurement technique. Results show that the use of strap rails or more robust I-beam sections in the vicinity of the IRJ to stiffen the support structure can significantly reduce the displacement and the subsequent dip angle seen at an IRJ. This potentially presents a means of improving the IRJ behaviour. Their impact becomes more significant for soft support conditions. Although these results are indicative for new IRJ conditions, field measurements indicate that the magnitude of deflection of IRJs is a result of the structural discontinuity of the rail, the dynamic P2 force, the wheel condition, the degraded ballast and it significantly increases with time under repeated load. Thus, it is recommended that careful field implementation and testing will indicate the effect of an external enhancement on the timely degradation of insulated rail joints.