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Dual Mode Sensing on Grout Structures with Piezoelectric Sensors



Monitoring of cracking in low-strength grout structures is of high interest to owners and regulatory agencies associated with infrastructure safety. Due to the variety of deterioration sources and locations of defects in infrastructure materials, there is currently no single method that can detect and address the potential sources globally. In this paper, we present a dual mode sensing methodology that attempts to integrate passive acoustic emission (AE) and active guided ultrasonic wave (GUW) inspection methods based on the use of permanently installed piezoelectric sensors (PES). Active or growing cracks emit AE waves that arise from the rapid release of strain energy. Analysis of these recorded signals provides early stage information about the cracking source with very high sensitivity. The “active” SHM approaches, on the other hand, use one sensor in the array to generate interrogation waves and the others as the wave receivers. By that means, quantitative information regarding the structural state of health and integrity can be extracted. A set of proof-of-concept tests are performed on a small grout specimen with two types of PES transducers. Two array imaging algorithms are developed for AE source localization and active damage detection, respectively. The methods demonstrated in this investigation provide promising means for imaging of cracking events both passively and actively.

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