The Behavior of Beams Reinforced with Patches Under Three-Point Bending: An Experimental Investigation

This study assesses the flexural performance of concrete beams repaired with externally bonded carbon-fiber-reinforced polymer (CFRP) patches under controlled damage conditions. Prismatic beams (7 × 7 × 28 cm) underwent three-point bending tests in four configurations: uncracked, uncracked-reinforced, cracked-unrepaired, and cracked-repaired. Pre-existing damage was caused by mid-span notches at a = 7, 21, and 35 mm. CFRP patches were placed on the tension face, and the ultimate load and failure mode were recorded. Repairing CFRP beams increased maximum load by up to 240% compared to unrepaired counterparts, and the failure characteristic changed from brittle shear to ductile flexural. Strengthening uncracked beams also yielded significant benefits. These findings show that patch-type CFRP reinforcement effectively recovers and enhances flexural performance across a wide range of crack severity, and they provide quantitative guidelines for determining repair levels depending on original crack depth.