Stiffness variations of railway tracks over rigid concrete and flexible steel culverts

Abstract

Over several decades it has been observed that additional maintenance and frequent track adjustments are needed close to bridges and rigid concrete culverts. Literature often suggests that these problems relate to a combination of differential settlements and variations in track stiffness, both which cause an increase in train-track interaction forces which over time adds to more differential settlements. This paper presents a study of displacement and stiffness related to train loads passing over rigid concrete and flexible steel culverts. Through numerical simulations supplemented by track measurements from field, the paper focuses on track displacements during regular train passage aiming for understanding how culverts affect the development of vertical track irregularities with time. The numerical simulations are carried out using the finite element (FE) program PLAXIS 2D. The challenge of transforming the problem into 2D is addressed and a pragmatic solution is suggested. Dynamic simulations are made of vertical point loads passing over rigid and flexible culverts to identify what designs and construction procedures that may lead to significant changes in track stiffness. In addition to numerical simulations, the performance of the track over six Norwegian culvert cases are considered using data from the measuring coach “ROGER 1000”. It is concluded that stiffness variations up to 65% do not lead to a growing problem with extensive track displacements and settlements, as long as the total rail deflections upon train passage is sufficiently small. This presupposes that modern design rules and specifications are used and followed when installing and backfilling around culverts, and that certain local conditions are met.