Remote Detection of Debonding in FRP-strengthened Concrete Structures Using Acoustic-Laser Technique

Abstract

Fiber-reinforced polymer (FRP) strengthening and retrofitting of concrete elements, such as beams, columns, slabs, and bridge decks, have become increa­singly popular. Nonetheless, rapid and reliable nondestructive testing techniques (NDT) that are capable of remotely assessing in-situintegrity of retrofitted systems are needed. Development of a robust NDT method that provides an accurate and remote assessment of damage and flaws underneath the FRP plates/sheets is required. In this study, a NDT based on an acoustic-laser system is proposed for remote detection of debonding in FRP-strengthened concrete structures. This technique utilizes the difference in dynamic response of the intact and the debonded regions in a FRP-strengthened concrete structure to an acoustic excitation, which is then measured using laser vibrometry. Feasibility and accuracy of the technique were investigated through a series of measurements on laboratory-sized plain, reinforced, and FRP-strengthened concrete specimens. It was shown that the difference in dynamic response could be captured by the acoustic-laser system and is in good agreement with simple calculations.