Abstract
The primary objective of this study is to investigate the feasibility of an innovative surface-mount sensor, made of a piezoelectric disc (PZT sensor), as a consistent source for surface wave velocity and transmission measurements in concrete structures. To this end, one concrete slab with lateral dimensions of 1500 by 1500 mm and a thickness of 200 mm was prepared in the laboratory. The concrete slab had a notch-type, surface-breaking crack at its center, with depths increasing from 0 to 100 mm at stepwise intervals of 10 mm. A PZT sensor was attached to the concrete surface and used to generate incident surface waves for surface wave measurements. Two accelerometers were used to measure the surface waves. Signals generated by the PZT sensors show a broad bandwidth with a center frequency around 40 kHz, and very good signal consistency in the frequency range from 0 to 100 kHz. Furthermore, repeatability of the surface wave velocity and transmission measurements is significantly improved compared to that obtained using manual impact sources. In addition, the PZT sensors are demonstrated to be effective for monitoring an actual surface-breaking crack in a concrete beam specimen subjected to various external loadings (compressive and flexural loading with stepwise increases). The findings in this study demonstrate that the surface mount sensor has great potential as a consistent source for surface wave velocity and transmission measurements for automated health monitoring of concrete structures.
Highlights
Introduction and MotivationSurface wave measurements have been widely used to develop non-destructive evaluation (NDE) techniques for concrete structures in civil engineering due to their useful features (Graff 1991)
The primary objective of this study is to investigate the feasibility of an innovative surface-mount sensor made of a piezoelectric transducers (PZT) disc as a consistent source for surface wave velocity and transmission measurements in concrete structures
The measured signals generated by a manual impact source shows good signal consistency in the frequency range of 10–30 kHz: the useful frequency range depends on the diameter of the steel ball used for impact sources
Summary
Surface wave measurements have been widely used to develop non-destructive evaluation (NDE) techniques for concrete structures in civil engineering due to their useful features (Graff 1991). Surface waves are non-dispersive, that is the wave velocity does not change with frequency This assumption is valid when the thickness H of the. Selecting an appropriate impact source is of great importance for successfully measuring surface waves in concrete structures. For plate-like concrete structures (deck, slab, wall, etc.), the ultrasonic surface wave (USW) technique has been demonstrated to be effective for evaluating material damages caused by many sources: ASR, DEF, freeze-and-thaw, and corrosion of reinforcing steel (Gucunski et al 2013). The frequency range of interest in the USW technique is a highfrequency range compared to the thickness of the tested object, in which surface waves are non-dispersive. In the case of a sound and homogenous concrete plate, the velocity of the surface waves will show little variability, while significant variation in the phase velocity will be an indication of the presence of a defect or other anomaly
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