Piezoelectric impedance transducers for structural health monitoring of civil infrastructure systems

In the past decade, the electromechanical impedance (EMI) technique employing lead zirconate titanate (PZT) impedance transducers has been successfully applied for structural health monitoring (SHM) of various engineering structures. In this technique, the PZT transducers act as collocated actuators and sensors and employ ultrasonic vibrations (typically in tens to hundreds of kHz range) to glean out a characteristic admittance signature of the structure. The admittance signature encompasses vital information governing the phenomenological nature of the structure, and can be analyzed to assess the structural damage. Owing to its costeffectiveness and high sensitivity to damage, the EMI technique has attracted intensive research attention in recent years. This chapter presents the recent theoretical and technological developments in the field of EMI technique. The EMI models based on PZT-structure interaction are first described, including analytical and numerical ones, followed by their applications for qualitative and quantitative structural damage assessment. Subsequently, the sensing region of PZT transducers is theoretically investigated and experimentally verified. Finally, practical issues related to field application such as repeatability of the PZT signature, adhesive layer between PZT and structure, and temperature effect are elaborated.