Maristella E. Voutetaki

Damage detection in concrete structures using a simultaneously activated multi-mode PZT active sensing system: numerical modelling

In this study, a structural health monitoring approach that integrates both electromechanical admittance (EMA) and guided wave (GW) techniques is presented. More specifically, the EMA technique is used for local damage identification, by employing a piezoelectric transducer (PZT) as admittance sensor. Simultaneously, the same admittance sensor is disturbed by selected elastic GWs launched by another PZT to monitor the damages located beyond the sensing area of the admittance sensor. The validation of the integrated approach is achieved by identifying the changes in electrical admittance signatures as measured on the surface electrodes of PZTs. These changes occur when damage alters the mechanical impedance of the examined concrete structure and when propagating GWs encounter structural damage. Finite element models of damages occurring in conventional unreinforced, steel-reinforced or fiber reinforced plastics-reinforced concrete specimens are investigated. Results illustrate that the proposed integrated technique is an efficient approach for damage identification of concrete structures.

Development of an electromechanical admittance approach for application in the vibration control of intelligent structures

The present work considers the possibility of vibration control of a distributed dynamical system, such as flexible plates using local piezoelectric (PZT) actuators/sensors and the electromechanical admittance concept. When PZT actuators bonded on structures are used in active vibration and acoustic control, the desired deformation field in the structure is obtained through the application of localized line forces and moments generated by applying an appropriate electrical field on the outer surfaces of the PZT patches. The electromechanical admittance generated at the electrical terminals of a PZT-driven smart structure is then extracted to synthesize a desired damping performance. This is achieved by a FEM-based minimization of the difference between the computed and the desired electromechanical admittance signature for investigated frequency ranges.

Developing a multi-mode PZT sensing solution for active SHM in concrete structures

Two damage detection and identification techniques are integrated in this work, including electromechanical impedance and guided waves methodologies, by using piezoelectric (PZT) patches bonded or embedded to the host structure. In particular, the electromechanical impedance has been used for identifying local damaged regions by monitoring the changes in structural mechanical properties, which are coupled with the electrical impedance of a PZT patch. In the guided wave propagation, one PZT patch acting as an actuator launches an elastic wave through the structure, which is can be measured by another PZT patch. The integration approach of these two methodologies is then straightforward because the same piezoelectric patch can be used for both methods. This integration approach is experimentally validated in this work by developing a reused and “multi-mode” sensing system for damage detection of concrete structures.