An integrated approach to dynamic analysis of railroad track transitions behavior

Abstract

Railway transitions like bridge approaches experience differential vertical movements due to variations in track stiffness, track damping characteristics, ballast settlement from fouling and/or degradation, as well as fill and subgrade settlement. Proper understanding of this phenomenon requires the integration of field instrumentation with analytical and numerical modeling. This paper introduces an integrated approach to dynamic analysis of the railway track transitions behavior using field instrumentation, analytical modeling, as well as numerical simulations using the Discrete Element Method (DEM). Several bridge approaches have been instrumented to monitor the track response on a problematic portion of the US North East Corridor (NEC), which is primarily a high-speed railway line with occasional freight traffic, carrying high-speed passenger trains operating up to a maximum speed of 241km/h. Previous publications by the authors have focused on findings from geotechnical instrumentation of railroad track transitions, as well as the validity of a fully coupled 3-dimensional track dynamic model and image-aided discrete element models. The primary contribution of the current manuscript involves the combination of these three components to propose an integrated approach for studying the behavior of railroad track transitions. Track response data from instrumented bridge approaches were used to determine track substructure layer properties and calibrate a fully coupled 3-dimensional track dynamic model. Loading profiles generated from this model were then used as input for a discrete element based program to predict individual particle accelerations within the ballast layer. The importance of modeling the ballast layer as a particulate medium has been highlighted, and the particle to particle nature of load transfer within the ballast layer has been demonstrated.