Keywords: railway bridges, dynamic monitoring system, strain gauges, fatigue assessment, local vibration fatigue.

This paper describes some of the tasks developed by the Laboratory of Vibrations and Monitoring (ViBest) of FEUP, in cooperation with the Portuguese railway administration, in the framework of the European FADLESS Project. The study was centred on a Portuguese riveted metallic railway bridge: the Trezói Bridge. The main developments are associated with the creation of finite element models that recreate with accuracy the dynamic behaviour of main elements and local structural details that are critical for fatigue safety [1]. This numerical work was based on several field tests: an ambient vibration test that allowed the calibration and validation of the main global modes [2], a temporary monitoring programme using strain gauges that permitted the evaluation of stress histories directly from the most stressed elements [3] and a long term monitoring programme addressing local elements that are more sensitive to local loading influence. These developments allowed the dynamic analysis and fatigue assessment of the most critical elements. Also, the strains measured on the rails allowed the estimation of axle spacing, axle loads and velocities using a methodology implemented in [4].

The work, described in this paper, led to the conclusion that, in this case, the most critical elements for vibration induced fatigue are not the principal elements since the cross-girders have a higher number of cycles and higher stress concentration. This is a result of the high sensitivity of these elements to each axle of the trains.

1

F. Marques, W. Hu, C. Moutinho, F. Magalhães, A. Cunha, "Evaluation of dynamic effects and fatigue assessment of a railway bridge supported by temporary monitoring", Eurodyn 2011 conference, Leuven, 2011.

2

F. Marques, "Evaluation of dynamic effects and fatigue assessment in metallic railway bridges", Master Thesis, Faculty of Engineering University of Porto, 2006. (in Portuguese)

3

Labest, "Monitoring of the behaviour of Trezói railway bridge under dynamic loads", Technical report, 2008. (in Portuguese)

4

I. Gonzalez, R. Karoumi, "Traffic Monitoring Using a Structural Health Monitoring System", Stockholm, Sweden, 2011.

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