A coupled approach for damage detection of framed structures using piezoelectric signature

High-frequency electro-mechanical impedance (EMI) signature is very sensitive to the local incipient damages in structures. However, extensive information on the nature of damages may not be available via EMI technique in its conventional non-model-based form. On the other hand, there is also little analytical work on the vibration modes of complex structures at ultrasonic frequencies. In this paper, a coupled approach combining EMI technique and a reverberation matrix method is proposed to quantitatively correlate damages in framed structures with high-frequency signature for structural health monitoring. The structural members are modeled as Timoshenko beams for flexural motion and as the classical longitudinal rods for axial motion. The PZT wafers, which are bonded to the beams, are also treated as one-dimensional in an axial vibration. A shear lag model is adopted to simulate the interfacial bonding between PZT patches and the host beam. An analytical expression for impedance (or admittance) related to response of the coupled model of PZT patch-bonding layer-host frame system is derived for the first time. Comparison study is presented with other established methods and theories. Based on this analysis, EMI signatures are extracted to identify the damages in framed structures theoretically. © 2007 Elsevier Ltd. All rights reserved.