Damage detection under environmental and operational variability using the cointegration technique

Within Structural Health Monitoring (SHM) framework based on Operational Modal Analysis (OMA), novelty analysis aims to detect structural anomalies by inspecting the time evolution of the modal characteristics of a structure subjected to ambient (unknown) excitations. However, in real applications, modal parameters are affected not only by structural changes, but also by environmental and operational variability (EOV), thus it is necessary to remove EOV effects before approaching any novelty analysis. The paper describes the vibrationbased SHM of Baixo Sabor dam (Portugal) involving the application of automated tools for modal identification during the first 2 years of monitoring. Within this context, two different novelty analysis procedures are adopted: (a) the well-known Hotelling T2 control chart based on PCA regression and (b) the less diffused Cointegration technique. Furthermore, several damage scenarios are simulated in a FE model of the dam, mainly with the purpose to compare the ability in the damage detection provided by the two different procedures of novelty analysis. Compared to traditional methods, Cointegration relies on more general operations and also permits to considerably reduce the training period where the structure is supposed to be in an healthy state.