Interfacial crack-induced debonding identification in FRP-strengthened RC beams from PZT signatures using hierarchical clustering analysis

The Electromechanical Impedance Method (EMI), based on the use of piezoelectric ceramic patches (PZT) constitutes one of the most promising methods for damage detection and location in the Structural Health Monitoring (SHM) field, more particularly for monitoring structures reinforced with novel FRP strengthening techniques. Many efforts have been made to obtain robust and reliable procedures that lead to a successful damage identification of experimental structures in general, but reliable data analysis and rational data interpretation are still challenges to be overcome in the case of debonding detection in strengthened structures, an approach being necessary that allows direct assessment of these experimental structures without the use of numerical models to compare with. In that way, clustering methods are a useful tool since they provide a classification of the data, based on some kind of similarity after a direct comparison between experimental results. With that purpose, in this study an innovative hierarchical clustering analysis has been proposed in order not only to obtain a set of clusters based on damage patterns found in experimental data obtained with PZT sensors, but also to achieve a graphical representation of this information so that the damage identification can be done qualitatively and quantitatively in an intuitive manner. The performance of the proposed approach has been investigated using three experimental tests including a full-scale reinforced concrete beam strengthened with FRP strip.