RAIL-BRIDGE INTERACTION EFFECTS IN SINGLE-TRACK MULTI- SPAN BRIDGES. EXPERIMENTAL RESULTS VERSUS NUMERICAL PREDICTIONS UNDER OPERATING CONDITIONS

摘要

This paper is devoted to the analysis of rail-bridge interaction effects in railway bridges under the circulation of moving trains. In a first approach, a bidimensional Finite Element model is implemented. The rail and the bridge are represented as Bernouilli-Euler beams, and a three-layer discrete track model accounting for the damping and flexibility of rail pads, ballast and subgrade is considered. In the model, several elastically supported spans are included, coupled by the presence of the track. First a sensitivity analysis is performed on the track parameters. A numerical receptance test is simulated on the rails showing that the track damping parameters influence the response only in the vicinity of the track natural frequencies, which are much higher than the bridge's. Then, the maximum acceleration of the bridge is evaluated under equidistant trains and consistent conclusions are extracted regarding the track parameters. Last, the number of spans included in the model is evaluated showing that limiting the model to one span does not necessarily lead to the highest response in terms of the bridge acceleration. Finally, the response of an existing two-span single-track bridge belonging to a conventional Spanish line is evaluated under the circulation of the Altaria Talgo train. Numerical predictions are compared to experimental results obtained in a recent campaign. The prediction of the vertical acceleration at the sensors located along the longitudinal symmetry axis is adequate. From the experimental results the coupling effect between the adjacent decks in each span is evident suggesting the need of analyzing this phenomenon with more sophisticated models.