Erol Tutumluer

Train-track interaction models are widely used to simulate the dynamic responses of train and track components. In a conventional train-track analytical model, the ballast layer is often simplified as mass blocks, interacting with other components through a spring and dashpot system. Such an idealization ignores the particle-level information, that is interaction of different sized and shaped aggregates and related degradation characteristics linked to fouling behavior of the ballast layer. On the other hand, realistic ballast models based on the discrete element method (DEM) can capture the particle-level information but require predefined external loading patterns as inputs to mimic the train passages. To overcome such drawbacks of train-track and DEM models, this paper proposes to couple the two calibrated models together to build a more realistic ballasted track model for predicting dynamic responses of the train and track. The coupled model was first validated with detailed field data collected from Amtrak’s Northeast Corridor. The validated model was then used to study the effects of crosstie spacing realizing that a smaller crosstie spacing than regular often results in a higher construction cost. Increasing crosstie spacing, however, was found to result in larger track displacements, crosstie accelerations and reaction forces, particle accelerations, and local average normal contact forces. Therefore, vibration patterns with a smaller crosstie spacing were more stable. Such observations suggest that crosstie spacing plays an essential role in controlling track dynamic responses, and an optimum crosstie spacing could be determined by using the newly introduced coupled model.