Experimental Study and Theoretical Analysis on the Flexural Behaviour of RC Beams Strengthened With Externally Bonded Reinforcement on Groove (EBROG) CFRP

The Externally Bonded Reinforcement on Grooves (EBROG) technique has recently appeared as a promising solution to provide better bond performance for strengthening Reinforced Concrete (RC) beams by using Carbon Fibre Reinforced Polymer (CFRP) rather than Externally Bonded Reinforcement (EBR). Due to the limited available results, there is still a need of further studies to better understand the behaviour of elements strengthened using this technique. This contribution aims to determine the feasibility of EBROG systems to delay or eventually prevent Intermediate Crack (IC) debonding of RC flexural elements strengthened with CFRP pre-cured laminates through experimental and theoretical points of view. For this purpose, an experimental programme including seven RC beams strengthened with CFRP and one control RC beam was performed. The beams were designed to theoretically fail by IC debonding following the fib Bulletin 90 simplified methodology. Two of them were strengthened using the EBR technique while five were strengthened using the EBROG methodology. Different internal tensile steel reinforcement, CFRP laminate width and EBROG groove distribution were used. The results in terms of load–deflection response, flexural capacity and modes of failure are presented and compared to analytical provisions. An improvement in the flexural performance of the strengthening system when using the EBROG technique was observed in all cases. The simplified approach from fib Bulletin 90 was found to be conservative for EBROG specimens.