Validation and calibration of a twin-deck bridge model under railway traffic

Abstract

This article describes the experimental and numerical evaluation of the dynamic behaviour of Cascalheira bridge located on the Northern Line of the Portuguese railway network. The bridge has a short span formed by two filler-beam half-decks each one accommodating a railway track. The study includes the development of a finite element numerical model in ANSYS® software, as well as in situ dynamic characterization tests of the structure, namely an ambient vibration test, for the estimation of natural frequencies, modes shapes and damping coefficients, and a dynamic test under railway traffic, particularly for the passage of Alfa Pendular train. The calibration of the numerical model of the bridge was carried out using an iterative methodology based on a genetic algorithm, allowing an upgrade of the agreement between the numerical and experimental modal parameters. Finally, the validation of the numerical model is performed by comparing the accelerations response of the structure under traffic actions, by means of numerical dynamic analyses considering the vehicle-bridge interaction, with the ones obtained by the dynamic test under traffic actions. The results of the calibrated numerical model showed a better agreement with the experimental results based on the accelerations evaluated in several measurement points located in both half-decks. In the validation process the degradation of the ballast located over the longitudinal joint between half-decks, demonstrated to be relevant for the accuracy and effectiveness of the numerical models.