Crack Detection of FRP-Reinforced Concrete Beam Using Embedded Piezoceramic Smart Aggregates

Abstract

In this paper, the authors present a stress wave-based active sensing method to detect the crack in FRP-reinforced concrete beams. The embedded smart aggregates (SAs), which utilize Lead Zirconate Titanate (PZT) as transducers, are employed in this research to generate and sense the stress wave. Three specimens are involved in the experimental program and each is made of concrete, longitudinal distributed reinforcement, steel stirrups, main bar (FRP bar or steel bar), and four SAs. A pair of SAs installed on the lower part of the main bar and the other pair of SAs mounted on the upper part of main bar are utilized to monitor the crack occurrence and development in the three test specimens. The signals received by the SA sensors are analyzed in both time domain and frequency domain. The wavelet packet energy is used to extract damage features. The applied load–vertical displacement curves of mid-span in the specimen are obtained. Experimental results show the test specimens experience crushing failure when the concrete compression exceeds its compressive strength. Increasing the contact area between FRP bar and concrete can effectively improve the cracking load of the FRP-reinforced concrete beam and reduce the cracking speed and depth of FRP-reinforced concrete beam; on the other hand, increasing the elastic modulus of the main bar can slow down the crack development of concrete on the upper side of the main bar and decrease the displacement of reinforced concrete beam during the loading test process. The research results show that the developed piezoceramic-based active sensing method, though low-cost, can monitor the crack-induced damage and estimate the process of damage degree in real-time, and has potentials to provide an early warning of crack occurrence and development for FRP-reinforced concrete beams.

Detecting of the Longitudinal Grouting Quality in Prestressed Curved Tendon Duct Using Piezoceramic Transducers

“…Each plot represents the frequencydomain signal received by a sensor under five different grouting states, including 0%, 50%, 75%, 90%, and 100% grouting. These frequency-domain signal diagrams indicate that the sensor signal has a sensitive frequency range from 50 kHz to 100 kHz, which is similar to the experimental findings in references [59,66]. The sensitive frequency range and PSD energy peak in the frequency-domain signals mainly depend on the characteristics of the structural responses.…”

“…In addition, wavelet packet decomposition can be performed on the signal sequence during the signal processing, and then the wavelet packet energy spectrum of the signals can be extracted. The study results show that the sensitivity and stability of the eigenvalues composed of wavelet packet energy spectrum are better than those in time-domain analysis and frequency-domain analysis [59,61]. Therefore, the above three signal analysis methods have their own focuses in the data process.…”

“…At present, the commonly used data processing methods of structural health monitoring mainly include time-domain analysis, frequency-domain analysis, and wavelet packet-based energy method. The time-domain signals are the original responses collected by the sensors, which can be described as a curve of signals with time [59]. Frequency-domain signals, transformed by Fourier transform from time-domain signals, are used to calculate the power spectral density (PSD) energy, which are closely related to the frequency composition of the signals.…”

Determination of the Real Cracking Moment of Two Reinforced Concrete Beams through the Use of Embedded Fiber Optic Sensors

“…By use of diffusing ultrasonic sensors, it has been possible to locate micro-cracks within the beam [16]. The stress wave technique with embedded smart aggregates in three samples of FRP reinforced concrete beams have provided satisfactory results in crack detection in the samples [17]. The use of plastic optical fibers to detect hairline cracks and ultimate failure crack in civil engineering structures has also obtained good results, even detecting the moment at which the structural element begins to crack and its evolution until the ultimate failure [18].…”

Feasibility Study on Grouting Compactness Detection in Sleeves Using Piezoelectric Transducers

“…Therefore, the signal processing method is vital, and wavelet packet energy (WPE) [18] method and Hilbert-Huang transform (HHT) [19] method are common signal processing methods. Jiang et al [20] presented a stress wave-based method to detect the crack in FRP-reinforced concrete beams. The research validated damage characteristics extracted in PZT signal by the WPE method were able to effectively monitor the crack occurrence and development.…”