Evaluating glass fiber reinforced composite sleepers to mitigate elastic fastening system spike fatigue failure: A finite element study

Abstract

North American railroads have experienced spike fastener fatigue failures due to spike overloading that have led to multiple derailments. Failures have primarily been found in timber sleeper track constructed with elastic fasteners. This is likely because the elastic fasteners change the load path, resulting in spikes becoming a primary component to transfer the longitudinal forces. Mitigation methods to prevent spike overloading have been limited and thus, this novel study seeks an alternative method leveraging engineered composite sleepers to reduce spike stress. This paper first documents and compares typical composite and timber sleeper properties as reported in the literature. Then, this paper describes the development and validation of a single spike-in-sleeper finite element model (FEM) used to investigate the interaction between the composite sleeper and spike. A glass fiber reinforced composite (GFRC) sleeper was selected due to its high elastic modulus and compressive strength reported in the literature. The validated model was used to quantify the effect of these critical material properties on spikes subjected to longitudinal loads. The GFRC’s stiffness and compressive strength values lead to a 30% reduction in the maximum spike stress when compared to spikes installed in timber sleepers. The reduced spike stress in the GFRC fell below the spike’s expected fatigue limit. Finally, this paper provides required compressive strength for given longitudinal loads to ensure the spike stress falls below the fatigue limit in different operating environments. This characterization of required composite sleeper strength properties can be used to advance track system mechanistic-empirical design.