Flexural performance of RC beams strengthened with HB CFRP plates: Experimental study and theoretical model based on the intermediate crack debonding

This paper presents a study on the flexural performance of Reinforced Concrete (RC) beams strengthened with Hybrid Bonded (HB) Carbon Fibre Reinforced Polymer (CFRP) laminates. Single-shear tests and flexural tests on RC beams strengthened with CFRP are examined, comparing both Externally Bonded (EB) and HB strengthening techniques with different anchor spacings. Results show that hybrid bonding improved the bond and flexural capacity in single shear and beam tests, respectively. A numerical model is developed to predict Intermediate Crack Debonding (ICD) in RC beams strengthened with HB CFRP laminates. The methodology is based on considering two different bond-slip laws, one for the EB and another for the HB CFRP portions. The proposed model is validated applying the bond-slip laws calibrated from the EB and HB CFRP single-shear tests to the flexural test results, demonstrating accurate prediction of ICD failure for both EB and HB CFRP specimens.