Vibration-based detection of structural damage in a railway bridge - a comparative study

This paper presents the comparison of several damage indicators to detect a damage in a railway bridge. Two damage scenarios and one environmental effect are introduced to the structure. In this study, modal-based damage indicators are directly computed from the results of a numerical modal analysis while the wavelet-based indicators are based on the dynamic bridge response of train passage excitation. The artificially generated experimental data are extracted from numerical simulations of a train passage on the bridge using the finite element method with a Newmark time integration. The finite element model represents the EU Erfttalstrasse, a bridge with 26.15m span width near Kerpen (Germany), which was extensively investigated in previous experimental campaigns. Based on experimentally obtained modal parameters the finite element model has been calibrated. The results show that wavelet-based damage indicators have higher sensitivities compared to natural frequencies or modal deflections. Some wavelet-based indicators are able to detect a very local small damage where almost no change in the modal parameters of lower modes can be observed. Although, modal-based damage indicators cannot detect very small damages, they show a monotonously increase to the damage's growth, an important property for damage quantification. All indicators are significantly affected by environmental effects, such as temperature. Therefore, a further procedure is needed to distinguish damage and non damage effects. However, this separation is not treated this contribution.