Bond behavior of prestressed FRP sheet-concrete joints: Comparison of EBROG and EBR methods

Abstract

When strengthening reinforced concrete (RC) elements with prestressed fiber-reinforced polymer (FRP), proper transfer of the prestressing force to the concrete surface must be assured. The current study investigated the bond behavior of specimens prepared with prestressed FRP sheets as well as the types of grooves used by employing a novel prestress-lap shear test. The prestressed and non-prestressed specimens were tested using a prestress-lap shear test and single-lap shear test, respectively, and the results were compared. A new groove classification technique was developed and results for the use of 5@15 mm (square grooves of 5×5 mm distanced center-to-center at 15 mm) and 10@20 mm grooves were compared with those for the conventional externally bonded reinforcement (EBR) method. The prestressing force was processed at 0%, 20%, and 30% of the ultimate strain. At all prestressing levels, specimens prepared in the 5@15 mm groove class performed better than those in the 10@20 mm groove class. The 5@15 mm groove class also required 53% less filling resin compared to the 10@20 mm groove class. At all prestressing levels, the specimens prepared through the grooving method (GM) using the externally bonded reinforcement on grooves (EBROG) technique performed better than those prepared by the EBR. The GM method allowed the 30% prestress force to be transferred to the substrate surface by engaging more depth of the concrete. The combined use of prestressed FRP sheets and GM to strengthen concrete specimens improved the overall performance of the joint compared to the specimen strengthened with non-prestressed FRP sheets and EBR.