UBC Theses and Dissertations
Practicality and capability of NDT in evaluating long-term durability of FRP repairs on concrete bridges Zadeh, Aidin Abdolrahim
Fiber reinforced polymer (FRP) repairs on concrete structures have become popular, but their long-term durability remains in question. The objective of this research project is to investigate the efficiency, practicality, and capability of non-destructive testing in assessing the durability of FRP repairs applied on concrete bridges that have been in service for some years. Three bridges were chosen as the best available case studies: (1) the Safe Bridge with sprayed FRP in British Columbia, (2) the St-Étienne-de-Bolton Bridge with four different FRP wrap products in Quebec, and (3) the Leslie Street Bridge with wrap carbon fiber reinforced polymer in Ontario. These structures represent a wide variation in severity of environmental exposure, length of time in service, type of strengthening, and type of FRP product. They also encompass flexural and shear strengthening of beams and strengthening of columns. Two non-destructive evaluation techniques, active infrared thermography and impact-echo, were chosen as the most suitable methods of bond evaluation. The results of these non-destructive techniques were compared with the actual bond strength for accuracy and consistency. To measure the actual integrity of the bond, direct mechanical pull-off tests were performed as a complementary semi-destructive method. Initial indications are that infrared thermography enables investigation of vast areas in a reasonably time-efficient manner and provides reliable qualitative results. Impact-echo is found to be ineffective in evaluating the FRP bond, as the method is incapable of assaying the material close to the impact surface. The direct mechanical pull-off test was found to be relatively accurate in providing quantitative results in environmentally mild testing conditions. Use of the direct mechanical pull-off test, in a small sample, as substantiation of the infrared thermography, significantly increases the reliability of the non-destructive technique. In general, infrared thermography showed that the bond between FRP and concrete in these structures is reasonably good in most areas, but it is strongly influenced by the placement technique, workmanship, exposure severity, and detailing.
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