Enhancing the shear capacity and ductility of RC beams using a hybrid strengthening system of anchored CFRP sheets and rubber supports: Experimental and numerical investigation

Abstract

Over the past four decades, carbon fiber-reinforced polymer (CFRP) sheets have been widely used to enhance the ultimate load capacity of reinforced concrete (RC) beams with low shear strength. However, their effectiveness in improving ductility is limited by premature debonding. This study investigates the use of carbon fiber-reinforced polymer–rubber support composites (CFRP-RSC) systems to enhance both load capacity and ductility. Twelve RC beams with shear span-to-depth ratios (a/d) of 1.1, 2.7, and 3.8 were tested under three-point loading. Three strengthening techniques were examined: conventional epoxy-bonded CFRP sheets, epoxy-bonded CFRP-RSC systems, and CFRP-RSC systems anchored with 6.0 mm diameter steel bolts. A 3D ABAQUS model was also developed to generate the load–strain behavior of steel reinforcement and assess ductility under different configurations. The results showed that conventional CFRP sheets experienced partial debonding, whereas CFRP-RSC systems reached rupture strain. Anchored CFRP-RSC systems effectively dispersed major shear cracks into multiple secondary cracks, reducing crack widths compared with conventional CFRP sheets. Beams strengthened with anchored CFRP-RSC systems exhibited ultimate load increases of 13.3 %, 9.3 %, and 21.5 % for a/d ratios of 1.1, 2.7, and 3.8, respectively, compared to their corresponding control beams. Ductility improvements were also significant, with increases of 32.6 %, 46.6 %, and 36.6 %, respectively, over beams strengthened with conventional CFRP sheets. The findings demonstrate that anchored CFRP-RSC systems are more effective than conventional CFRP sheets in simultaneously enhancing both load capacity and ductility of RC beams.