Integration of Electro-mechanical Impedance and Global Dynamic Techniques for Improved Structural Health Monitoring

This article proposes the simultaneous application of the local electro-mechanical impedance (EMI) and the global dynamic techniques using the same set of piezoelectric ceramic (PZT) sensor patches for improved health monitoring of structures. It describes an experimental study conducted on a two-story reinforced concrete frame structure using PZT patches embedded in the structure. The global dynamic technique, which is based on global frequency changes, is effective in low frequency range only, due to which an incipient damage (such as hair crack) cannot be detected by it. On the other hand, the EMI technique, which works in the kilohertz range, is very sensitive to incipient damage. The initial cracks were successfully detected by the EMI technique whereas more severe type damages were identified and suitably quantified by the global dynamic techniques. Selected inputs, chosen from the extracted equivalent parameters, namely stiffness and damping changes (EMI technique) and the damping ratio (global technique), were used to train an artificial neural network, whose outputs were the severity and the location of the damage. The simultaneous use of the two techniques results in an improved structural health monitoring. This approach is very sensitive and cost effective to detect damages ranging from incipient to severe types in the civil structures.