Experimental investigation on RC beams strengthened with FRP sheets by drilling method

One of the most important applications of FRP sheets is the flexural strengthening of concrete beams by bonding these materials to the beam's tensile surface. The most common problem in this strengthening method is the early debonding of the sheet from the surface of the concrete, which results in a early failure before the final strength of the beam is obtained. The most common method for preparing concrete surfaces for proper bonding of composite sheets is the Externally Bonded Reinforcement (EBR) method, which, in addition to environmental pollution, does not completely eliminate the problem of early debonding of FRP sheet. This paper examines the possibility of replacing the proposed drilling method with mounting screws instead of EBR method. In this research, 10 samples of beam with dimensions of 150 × 300 × 1700 mm were tested under 4-point bending. The samples were tested by changing the number of layers and the method of mounting the sheets and in three samples with Simultaneous flexural and shear strengthening. Using the proposed method, the debonding problem was completely eliminated in all samples. The greatest increase in flexural strength was related to the sample, which, simoltanously strengthened in shear with FRP bars by NSM method.The effect of removing the bond in the middle part of the frp sheats was also investigated. The installation without bond of the sheets in the middle part, in addition to delaying the rupture of the sheets, increased the ductility.