Published Paper Details:

- Any civil structure require Health Monitoring with certain aging or after any repeated loading like earthquake. The EMI technique is a relatively new technique for SHM. The mechanical impedance Z of the host structure is function of the structural parameters viz. stiffness, the damping and the mass. Any damage to the structure will cause these parameters to change, resulting in change in mechanical impedance Z. Consequently, the electro-mechanical admittance will undergo changes, and serves as an indicator of the health of the structure. Due to high frequency of excitation, the EMI has very high sensitivity to damage, typically of the order of the ultrasonic techniques. The technique can detect flexural and shear crack before they can be conspicuously identified through naked eyes . In the EMI technique, a PZT patch is bonded to the surface of structure using high strength epoxy adhesive or embedded in structure whose health is to be monitored. The signature of the PZT patch is acquired over a high frequency range (30-400kHz) with the help of LCR meter or impedance analyzer. The signature is complex in nature, consisting of the real and the imaginary components called conductance and suspetance respectively. The signature in the healthy condition forms the reference signature. In future, when it is required to assess the health of structure, the signature is acquired again and compared with reference signature. Changes in signature from reference signature signify the crack/damage in the structure.