Shear contribution of beams of different sizes strengthened in shear with anchored CFRP strips

Carbon-fibre-reinforced polymer (CFRP) materials can be used as structural reinforcement in engineering projects, but its effectiveness is jeopardised by debonding of the CFRP. Anchoring of the CFRP is thus crucial for efficient shear strengthening. The effect of anchoring on the shear resistance of nine CFRP U-wrapped concrete beams with varying shear span-to-depth (SSD) ratios (1.0, 1.5 and 2.0) and depths of 300–900 mm was investigated in this work. Nine unanchored beams and nine plain (without CFRP wrapping) concrete beams were also included in the comparison, considering the influence of the beam effective depth and the SSD ratio, with reference to prior research. An evaluation of the shear contribution of the CFRP wrapping was conducted, particularly for cases involving large dimensions and diverse SSD ratios. The anchoring effect was found to be most pronounced in small-scale beams with a large SSD ratio, demonstrating an improvement of over 60% compared with the CFRP shear-strengthened beam without anchoring. In contrast to beams without CFRP wrapping, the shear performance was enhanced by approximately 90%. Additionally, formulas for calculating the shear capacity from different national specifications were analysed and compared. A new calculation method for CFRP shear resistance was established and its accuracy was verified.