A Robust Methodology for the Standoff Condition Assessment of FRP-Retrofitted Concrete Systems

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Fiber-reinforced polymer (FRP) strengthening and retrofitting of reinforced concrete elements, such as beams, columns, slabs, and bridge decks have become increasingly popular. To remotely assess in-situ integrity of such retrofitted systems an efficient and effective nondestructive testing technique (NDT) is needed. In this research a robust standalone NDT approach utilizing an airborne acoustic wave focused on the damaged area will be developed to detect the damage and flaws underneath the FRP plates/sheets. Laboratory specimens with various defect configurations will be subjected to acoustic arrays from close as well as long distances. Dynamic responses produced by the defects will be collected by laser Doppler vibrometry (LDV). The proposed method is based on the concept that debonding damages and concrete voids in the FRP-concrete system cause local vibration anomalies that are considerably different from those caused by intact regions and that they are direct functions of the damage dimensions and mechanical properties.The proposed research represents a multi-disciplinary effort integrating knowledge from mechanics of composite concrete, wave propagation in solids, acoustic and laser technologies, and computer science. It involves numerical simulation, pattern recognition, signal processing and imaging in conjunction with complex composite material system behavior. Thus, the project will have a strong intellectual component with potential to advance scientific knowledge in these multi-disciplinary areas, and significant contribution toward the development of a robust non-contact technique for integrity assessment of FRP-bonded concrete structure. The findings from this research will be extensively disseminated through research publications and integrated educational materials through internet. The research activity will provide advanced training and research opportunity to the students working on this project.