Structural performance of RC beams with openings shear strengthened by hybrid techniques (EBR/EBRIG)

Abstract

Creating the openings in the existing reinforced concrete (RC) beams causes sudden deterioration, especially in the shear zone. This study investigates the effectiveness of a novel strengthening technology using externally reinforced fibre-reinforced polymer (FRP) strips in groves (EBRIG) on the shear behaviour of RC beams, compares it to that of externally reinforced (EBR) strips, and uses hybridisation between them to address the weakness brought on by the presence of an opening in the shear zone. Also, an innovative anchorage mechanism is suggested and studied to postpone the beginning of the strengthening system’s debonding. The strengthening material used in this research is glass fibre-reinforced polymers (GFRPs). For this study, 11 RC beams with an opening and a control beam without an opening, each measuring 120 × 300 × 2600 mm in size, were cast and subjected to the four-point loading test. All test beams had the same geometry and reinforcement details. The effect of the following parameters was investigated in this study: the dimension of the opening (square ‘150 × 150’ or rectangle ‘100 × 300’ mm), the strengthening technique used (externally bonded reinforcement [EBR], EBRIG and hybrid technique ‘EBRIG + EBR’) and the wrapping configuration of the strengthening (fully warped strips or U-shaped sheets with anchors). All techniques used raised the efficiency of shear resistance to approximate the fading effect of the opening, especially the technique of hybridising EBRIG and EBR. All strengthened beams showed an increase in the ultimate shear capacity ranging from 74% to 142% compared with the reference beams with the opening. The EBRIG technique shows numerous advantages over the EB system and can employ the strength of FRP materials. It also deals with the problems of weather factors that were facing EBR, and this is because of the covering that protects in the EBRIG technique. The technique to hybridize EBRIG and EBR was more effective at withstanding shear.