Abstract
Piezoelectric ceramic Lead Zirconate Titanate (PZT) based electro-mechanicalimpedance (EMI) technique for structural health monitoring (SHM) has been successfullyapplied to various engineering systems. However, fundamental research work on thesensitivity of the PZT impedance sensors for damage detection is still in need. In thetraditional EMI method, the PZT electro-mechanical (EM) admittance (inverse of theimpedance) is used as damage indicator, which is difficult to specify the effect of damage onstructural properties. This paper uses the structural mechanical impedance (SMI) extractedfrom the PZT EM admittance signature as the damage indicator. A comparison study on thesensitivity of the EM admittance and the structural mechanical impedance to the damages ina concrete structure is conducted. Results show that the SMI is more sensitive to the damagethan the EM admittance thus a better indicator for damage detection. Furthermore, this paperproposes a dynamic system consisting of a number of single-degree-of-freedom elementswith mass, spring and damper components to model the SMI. A genetic algorithm isemployed to search for the optimal value of the unknown parameters in the dynamic system.An experiment is carried out on a two-storey concrete frame subjected to base vibrations thatsimulate earthquake. A number of PZT sensors are regularly arrayed and bonded to the framestructure to acquire PZT EM admittance signatures. The relationship between the damageindex and the distance of the PZT sensor from the damage is studied. Consequently, thesensitivity of the PZT sensors is discussed and their sensing region in concrete is derived.
Highlights
The development of real-time, in-situ structural health monitoring (SHM) and damage detection techniques has been studied to prevent catastrophic failures and to reduce the cost of maintenance and inspecting tasks
The root mean square deviation (RMSD) indices based on the raw Piezoelectric ceramic Lead Zirconate Titanate (PZT) admittance and the structural impedance which is extracted from the raw admittance signature have been evaluated for a concrete frame structure
The damage indices based on the real parts of the structural impedance and the PZT admittance are more suitable for damage detection than those based on the imaginary parts
Summary
The development of real-time, in-situ structural health monitoring (SHM) and damage detection techniques has been studied to prevent catastrophic failures and to reduce the cost of maintenance and inspecting tasks. The impedance-based SHM technique has been developed by using the electromechanical (EM) coupling property of the piezoelectric materials [1]. It has involved into a new nondestructive evaluation (NDE) method. This paper proposes a dynamic system model to associate the damage state with the changes of structural properties. The EMI damage detection method is based on the principle of EM coupling effect between the host structure and the bonded PZT sensor. Any change in the EM admittance signature is an indication of a change in the structural integrity which may be caused by the presence of structural damage
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