DETECTION OF DEFECTS BETWEEN FRP SHEET AND CONCRETE BY INFRARED THERMOGRAPHY METHOD

Delamination between FRP sheets and concrete, which might be caused by inappropriate works or deterioration due to a time elapse, decreases bond strength between FRP sheets and concrete, and also decreases the strength of the structural element reinforced with FRP sheets. Therefore, these defects must be accurately detected and be properly repaired. This paper concerns the detection of defects between FRP sheets and concrete by measuring thermal distribution of the surface using an infrared thermography method. It is confirmed from the basic experiments using heated or cooled specimens that the detection of defects is influenced by the type and number of FRP sheets, as well as the thickness of defects. It is shown from experiments in the open air that defects can be detected from the difference between specimens and circumferential air in both clear and cloudy weather. Moreover, a non-steady heat transfer analysis by FEM is conducted and it is confirmed that the analysis can well simulate the experimental results.