Effect of Longitudinal Fastener Stiffness and Fastening System Loading


Over the past 20 years, there have been at least 10 derailments due to spike fatigue failures in North America. Researchers believe that fatigue failure is caused by overloading of the spike through a combination of lateral and longitudinal loads. The literature also indicates that vertical load fastener friction must also be considered when estimating failure locations. Further, though there has been research to quantify the vertical, lateral, and longitudinal fastener forces in track that has experienced spike failures, there is a need to account for additional fasteners and track locations. Additionally, because the fastening system can affect the track stiffness, laboratory experimentation was performed to quantify stiffness of multiple fastening systems. This data was input into an analytical model to quantify the effect of stiffness on fastener loading. The laboratory data indicates that there is significant variance in fastening system stiffness within, and between, systems. However, this variation in fastener stiffness has minimal effect on the load transferred to the fastening system. More work is needed to validate this in the lab or field given variability within a system could lead to stress concentrations that are not fully captured using the current idealized analytical method. The characterization of longitudinal stiffness of multiple fastening systems as presented within this paper can be used to advance track mechanistic-empirical design and improve rail neutral temperature prediction and track buckling models.