Evaluation of data-driven methods for damage detection under environmental effects – application to a cable stayed bridge
Abstract »Daily and seasonal temperature variations exert a significant influence on the structural re-sponse of bridges. Several long-term monitoring studies have reported that temperature variations can produce strains, displacements or rotations of the same order of magnitude, or even larger, than those produced by dead or live loads. In this context, the aim of this study is to evaluate the possibilities of detecting structural damage through the analysis of the thermal response of a cable stayed bridge on which a comprehensive long-term monitoring system has been installed.
To properly characterize the bridge thermal action on its three components (uniform, linear and non-linear), a finite element thermal analysis is performed using data from a meteorological station nearby the case study (providing the wind velocity, radiation and ambient temperature values) and the temperature readings inside the box-girder obtained from the bridge monitoring system. The results of the thermal model are compared with the experimental data from the temperature sensors embedded in the concrete and reasonable agreement is found. Finally, several damage scenarios are simulated and the response of the bridge to the thermal actions is obatined by means of a finite element mechanical model previously validated with data acquired during the construction stages and during a load test.
For the purpose of evaluating the ability of detecting damage using the structural response to thermal loads, Multilinear Regression Analysis (MLR) and Principal Component Analysis (PCA) are applied both to the simulated and to the experimental data sets. The experimental data corresponds to a monitoring period of about one year and comprises measurements of the stay-cable forces, longitudinal joint displacements, vertical deck displacements, rotations and strains. The performance of the two methods is compared and some conclusions are put forward regarding the feasibility of early damage detection in the selected cable-stayed bridge using the adopted methodologies and the installed monitoring system.