Railway Bridge Transition Case Study

Railway track transitions at bridge approaches are often significant maintenance problems. Problems arise from settlement of the track at the bridge-approach along with stiffness and damping disparity between the fixed-structure and the approach. The substructure (ballast, subballast, subgrade and drainage) of the bridge-approach profoundly affects the settlement, stiffness and damping of the track at the transition location. To better characterize the condition and behavior of certain bridge approaches under heavy-axle load traffic and to also advance the state-of-the-art in bridge and track transition design and maintenance, two undergrade bridges were investigated on a major heavy axle load (coal and mixed freight) line in a mountainous territory in the eastern United States. The investigation consisted of standard test boring sampling, SPT and CPT testing along with track modulus and gage strength testing. This paper presents a case study of the investigation and analysis performed for the bridges at the project site. Also included is information on the past maintenance history and operating environment specific to the two bridges. Potential solutions are presented that are intended to arrest any settlement of the bridge approach and also achieve stiffness compatibility between the bridge and bridge-approach.