Methods to mitigate railway premium fastening system spike fatigue failures using finite element analysis

Railroad track fasteners work as a system, in conjunction with the sleeper, to maintain gauge, transmit loads, and resist lateral and longitudinal rail movement. Timber sleeper elastic fastening systems have shown benefits by preventing rail rollover derailments and reducing spike killing. However, these systems have experienced broken spike failures leading to at least 10 derailments over the past 20 years. Recent studies focusing on the cause of the failures have indicated that the spikes fail in fatigue and these fatigue failures are driven by the addition of longitudinal loads the spikes carry. Further, due to the nature of the elastic fastener, the wave-action of the rail separates the plate from the sleeper, as opposed to the rail from the plate, thus eliminating the load transferred by friction. This study quantifies the effect of fastening system design changes on spike stress and the load required to exceed the spike endurance limit. Specific design changes investigated in this study include increasing spike cross-sectional area, comparing spike type (cut vs screw), varying the spike load location, controlling the development of friction between the sleeper and plate, varying spike engagement and finally, adjusting the quantity of spikes at a given rail seat. Finite element analysis (FEA) was used to quantify these effects and multiple 3D models were developed and used. Results indicate that the two most effective methods to reduce spike stress and increase the required load to exceed the spike's endurance limit, and thus mitigate spike fatigue failures, would be to ensure spike engagement between the plate and spikes and develop friction between the plate and sleeper (e.g. add spring washers, etc.). Future fastening system designs can incorporate these, and other findings, to mitigate spike fastener failures to ensure the full value of timber sleeper elastic track fastening systems is realized.