Theoretical and experimental study on notched steel beams strengthened with CFRP plate

CFRP external bonding is an alternative technique to repair or strengthen notch damaged steel beams. However, the premature debonding failure caused by the stress concentration at the notch location reduces the effectiveness of this reinforcement technique. This paper presents an integrated closed-form solution for obtaining the interfacial shear and normal stresses in steel beams strengthened with a CFRP plate. Simple expressions of the maximum interfacial stresses at the notch locations, the adhesive hollows and the plate ends are given. A parametric study indicates that the maximum stresses at the notch locations increased with the notch depth and the applied bending moment on notched cross-sections, but reduced with the thickness of the adhesive. An experimental study of model-scale CFRP bonded steel beams was conducted as well. The test results show the strength of the notched beam can be improved almost twice by the CFRP plate strengthening, while the brittle fracture caused by intermediate debonding initiated from the notch location limits the ductility enhancement of the retrofitted beams. The good agreement between the longitudinal strain distributions in the CFRP plate obtained from the tests and the corresponding analytical results demonstrates the validity of the theory.