Defect visualization in FRP-bonded concrete by using high speed camera and motion magnification technique

Abstract

High speed camera has the unique capacity of recording fast-moving objects. By using the video processing technique (e.g. motion magnification), the small motions recorded by the high speed camera can be visualized. Combined use of video camera and motion magnification technique is strongly encouraged to inspect the structures from a distant scene of interest, due to the commonplace availability, operational convenience, and cost-efficiency. This paper presents a non-contact method to evaluate the defect in FRP-bonded concrete structural element based on the surface motion analysis of high speed video. In this study, an instant air pressure is used to initiate the vibration of FRP-bonded concrete and cause the distinct vibration for the interfacial defects. The entire structural surface under the air pressure is recorded by a high-speed camera and the surface motion in video is amplified by motion magnification processing technique. The experimental results demonstrate that motion in the interfacial defect region can be visualized in the high-speed video with motion magnification. This validates the effectiveness of the new NDT method for defect detection in the whole composites structural member. The use of high-speed camera and motion magnification technique has the advantages of remote detection, efficient inspection, and sensitive measurement, which would be beneficial to structural health monitoring.