Shear strengthening of simply-supported deep beams with openings incorporating combined steel-reinforced engineered cementitious composites and externally bonded carbon fibre-reinforced polymer sheets

In many practical applications, openings in deep beams are essential for accommodating services like ducts, pipes, and cables. However, these openings can significantly disrupt the load transfer mechanism and reduce the shear strength of the beam, potentially leading to premature failure. Consequently, strengthening techniques are employed to restore or enhance deep beams’ load-carrying capacity and structural performance with openings. This research investigates the effectiveness of a novel strengthening approach that combines reinforced engineered cementitious composites (ECC) and externally bonded carbon fibre-reinforced polymer (CFRP) sheets for enhancing the shear strength of simply-supported deep beams with openings. The ECC reinforced with galvanized steel wire mesh (GWWSM) was applied to the beam sides with steel anchors to connect it to the existing concrete. After ECC hardening, CFRP sheets were glued to the ECC surface. ECC is a highly ductile, fibre-reinforced cementitious material with superior crack resistance and energy dissipation capabilities. At the same time, externally bonded CFRP sheets provide additional shear reinforcement and confinement due to their high tensile strength. An extensive experimental programme was conducted to investigate the proposed strengthening technique. Six reinforced concrete (RC) deep beam specimens, forming two groups, were fabricated and tested to investigate the effect of opening shape and size on shear capacity. Both rectangular and circular openings were considered in this study. Results are presented as a load-deflection response, crack pattern, and failure mode. A nonlinear finite element model was developed to simulate the strengthening technique and was validated using the experimental findings. The findings from this research provide valuable guidelines for enhancing the performance of deep beams with openings using reinforced ECC and externally bonded CFRP sheets.