Efficacy of NSM hybrid FRP strips for shear strengthening of rc deep beams

Abstract

This paper presents an experimental study on the efficacy of near-surface mounted (NSM) hybrid carbon/glass fiber reinforced polymer (FRP) strips for the strengthening of shear-critical reinforced concrete (RC) deep beams. For this purpose, the experimental investigation was carried out on four medium-scaled RC deep beams. Three beams were strengthened with hybrid NSM-FRP strips, while one beam was kept unstrengthened to act as a reference. All beams were tested as a simply supported system under displacement controlled three-point loading test. The test variable includes the geometric reinforcement ratio of the FRP system. The test results revealed that the NSM-FRP strengthening system is effective in increasing the shear strength of deep beams, up to 55.8% increase in the shear strength was observed. In addition, the results showed that the NSM-FRP had the potential to mitigate the premature debonding between the concrete and the strengthening material, which is commonly observed in the conventional externally bonded technique. The strengthening system has also enhanced the deformational characteristics of the strengthened deep beams.