Studies on the track input to the response of in-service insulated rail joints

Insulated Rail Joints (IRJs) are vulnerable to heavy axle loading as evidenced by their frequent replacement in short periods due to various modes of failures they exhibit under the passage of loaded wheels aggravated by the local condition of the track. As the wheel loads and track conditions can be highly variable, IRJs exhibit highly variable service life. The IRJs used in Australia are assembled in factories with high standards of quality control procedure as outlined in manuals and standards; however, their service life varies significantly even under similar traffic condition, which is of a major concern to the rail industry and the society and allied industries that depend on the rail transport. A research hypothesis on the effect of the support system (track) to the short and variable service life of IRJs is, therefore, formulated and examined in this thesis. In spite of the significant role the IRJs play to the control of signalling system and their low and highly variable service life, there is a paucity of literature with regard to the actual mechanical behaviour of the in-service IRJs. This thesis aims at bridging the gap in the knowledge. An extensive field test was conducted on an in-service heavy haul corridor in Australia with the specific aims of understanding the effects of track input to the response of the IRJs. Data on the wheel-rail forces, rail strains, sleeper accelerations and ballast pressure signatures are determined from the experiment. The data are systematically employed to analyse the mechanical behaviour of the IRJs resting on different support conditions relative to a Reference Rail (Ref rail) subjected to the same traffic loading. One of the instrumented IRJs and the Ref rail have been monitored over 16 months to examine the change in their responses under accumulated traffic. A track model containing an IRJ is developed in the GENSYS multi-body dynamic system framework. The developed model is calibrated against the data measured on the Ref rail and then validated using the data from the IRJs. GENSYS is widely used in train dynamic analysis and its usage in detailed track component modelling and examination of performance at component level is first of its kind; the results of which unearth the powerfulness of the platform for track dynamic analysis, albeit the model is complex. The validated GENSYS model is then employed to simulate various scenarios of track support conditions including varied levels of damage beneath the IRJs. The sensitivity of loading and responses of IRJs to the change in IRJ component properties as well as different track support parameters are analysed. Various conditions of deteriorated track including sleeper void (hanging sleepers) and geometry dip are investigated; their effects on the loading and responses of IRJ are discussed. Analysis of results obtained from experiments and numerical simulations have resulted in valuable conclusions on the effects of track input to the response of IRJs, the key of which are as follows: vi 1- The loading and responses at the IRJ are significantly higher than the regular track. 2- The high loading and response scenario adjacent to IRJ can partly be compensated by the modification of track/support parameters at IRJ. 3- Track/support parameters are more effective than the design parameters of the components for improved performance of IRJs. 4- When a new insulated rail joint is perfectly installed in a well maintained rail track, the dynamic wheel loads are only excited due to the joint gap under the train passages; however, over time the ongoing degradation of track significantly amplifies the IRJ responses. These conclusions have benefits for developing better practices for installation/maintenance of IRJs in track.