Delamination detection in concrete bridge decks using the constant phase approach in the analysis of air-coupled impact echo data
Creators: name: Almallah, Najjiya
Publisher: name: No Publisher Supplied
Year: 2022

description: For the economic management of aging highway bridges, it is essential to detect the early signs of deterioration. Delamination is one of the most common problems in concrete bridge decks commonly detected by the impact echo method. The impact-echo (IE) is a nondestructive testing method used to detect internal defects, primarily delamination, in concrete elements. The amplitude spectrum is commonly used to determine the dominant frequency peak, or the thickness frequency, that gives information of the element thickness or is an indication of the presence of a defect or anomaly. To speed up the data collection process, an air-coupled version of the IE test has been recently used. The amplitude spectrum of the air-coupled IE signal is usually contaminated with multiple peaks from acoustic and ambient noise, and the localization of the thickness frequency is not straightforward. Different preprocessing and postprocessing techniques were introduced to improve the interpretation of IE data, but most of these techniques are subjective (operator dependent). This dissertation proposes an automated (operator-independent) detection and visualization of concrete internal defects based on Lamb wave theory which relates the dominant frequency of air-coupled IE data to the zero-group velocity mode (S1-ZGV). Therefore, the phase spectra of IE signals, recorded from multiple air-coupled sensors, are used to locate internal defects in concrete elements. The phase spectra of these signals are stacked together to obtain a 2D frequency-sensor offset profile. This profile shows a constant phase at the thickness mode frequency. The proposed technique is named the Constant Phase Impact Echo CPIE, its performance is examined using synthetic data of decks with shallow, intermediate, and deep embedded delaminations simulated using ABAQUS 2018 software. Results demonstrate that the proposed technique has satisfactory performance in detecting the presence of delamination, its depth, orientation, and dimensions.Synthetic data is also used to investigate the sensitivity of the CPIE to different parameters including sensor array orientation, its distance from impact location, its height, and the distance among its sensors. This part of the research shows how the effectiveness of the constant phase impact echo technique is related to these parameters and how to further improve its performance.An indoor experimental comprehensive study was conducted by applying the CPIE algorithm to the floor of the Laboratory for Sustainable Infrastructure (LSI) at Rutgers University. Various types of impactors, sensors, and experimental configurations were used to validate the results of the CPIE algorithm. Furthermore, the performance of the CPIE algorithm was compared to two other multi-sensor algorithms used in the IE testing, namely the Multi Cross-Spectral Density (MCSD) and the Time Domain Summation (TDS). The results reveal that both the TDS and the CPIE techniques outperform the MCSD IE technique. The CPIE shows a performance advantage over the TDS in rejecting acoustic noise.Another experimental study was conducted in an outdoor bridge deck with simulated embedded defects. Results demonstrate that the CPIE technique has satisfactory performance in detecting the presence of delamination, its depth, and its dimensions. The CPIE algorithm shows superior performance, especially in the presence of acoustic noise. This is because it exploits the S1-ZGV feature of the thickness frequency, in an explicit way, by searching for the frequency at which the phase from all the sensors along the radial offset becomes constant.