A Method for Using Transformed Track Deflection Data to Assess Dynamic Forces at Railway Track Stiffness Transitions

Abrupt changes in railway vertical track support stiffness result in dynamic impact forces that can accelerate the degradation of the running geometry of the track. This results in more frequent maintenance and shortened track component lives. A method for utilizing near-continuous vertical track deflection measurement data to assess dynamic forces at track transitions is developed. This method determines the proportional forces associated with the stiffness variation and running track surface geometry for actual conditions in track. Basic mechanics of beam on elastic foundation for variable track stiffness, and a simplified dynamic simulation model that uses a vertical velocity input excitation, are used to determine dynamic impact forces for idealized step changes in track stiffness. Near-continuous vertical track deflection inspection data is transformed using the Hilbert-Huang transform to separate the velocity input into components that identify the proportion of the force at the wheel/rail interface associated with the running rail geometry and the proportion associated with stiffness variation in the actual track support. Simulation of actual inspection data showed that an increase in vertical force of 5–10% can be expected due to stiffness transitions, while local deformations can result in an increased force of 50% + . The resulting method was then applied to 150 km of vertical track deflection data to prioritize maintenance for local areas of excessive deflection directly from the vertical track deflection data. This in turn can be used to determine maintenance and typical transition rehabilitation measures for stiffness transitions associated with bridges, grade crossings, and culverts.