Remote defect detection of FRP-bonded concrete system using acoustic-laser and imaging radar techniques

•A nondestructive testing scheme combining acoustic-laser and imaging radar techniques is proposed.•The defect characterization of FRP-bonded concrete structure is conducted.•Both global and local response of FRP-bonded concrete structure are evaluated.•The structural health can be monitored effectively by the proposed detection scheme.

Two different remote nondestructive testing (NDT) techniques, the acoustic-laser and imaging radar techniques, are studied for near-surface defect detection in fiber-reinforced polymer (FRP) retrofitted systems. In the acoustic-laser technique, the targeted structure is excited by acoustic waves, while vibration data on a measurement point is remotely collected. In the imaging radar technique, radar signals (electromagnetic waves) are remotely emitted toward the target structure and measured when they are reflected from the structure. Three FRP-bonded concrete cylinders with various defect sizes were fabricated for laser and radar measurements. The pros and cons of these two techniques are described with the support of experimental result.

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