Interfacial debonding in steel beams strengthened by externally bonded CFRP

The interfacial debonding at the plate ends is the most common failure mode in a carbon fibre reinforced polymer (CFRP) strengthened steel beam due to the high stress concentration there. This paper presents the results of a theoretical and experimental study on the interfacial debonding of the steel beams reinforced with CFRP plates. An analytical solution was developed to calculate the interfacial shear stress between the steel beam and the CFRP plate. The shear stress-slip relation of the bonding layer was simulated by a bilinear model. Three specimens were tested under threepoint bending. Two strain gauges were mounted at the ends of the plate bottom. If the effect of the spew fillet and the normal stress are ignored, the curves of strain recorded from the tests can be simplified to a bilinear model as well, which validates the theoretical results. When the strain is close to zero, the interfacial debonding initiated at the end of the plate. The agreement between the debonding loads obtained from the analytical solutions and the tests is good, which demonstrate that the presented analytical solution can predicate the debonding load correctly.