Simple equations of shear and normal stresses at the ends of CFRP plate bonded onto steel member

Recently, repair or strengthening of steel members by externally bonding Carbon Fiber Reinforced Polymer, CFRP, plate have been reported. While bonding CFRP plate can easily achieves increase in stiffness and strength, the debonding of CFRP plate from its ends is concerned. In Japan, the CFRP plates are also employed for enhancement of steel members with deterioration, fatigue cracks or low load-carrying capacity. Nevertheless, the verification method for debonding of CFRP plate has not been established. In this research, to encourage the development of verification method for debonding of CFRP plate, the differential equations of steel member with CFRP plate under typical load conditions, which are concentrated load and uniformly-distributed load, were derived and solved. As a result, the estimation equations of shear and normal stresses in adhesive at CFRP plate ends under typical load conditions were given. The shear and normal stresses at CFRP plate ends were provided as the functions of cross-sectional forces acting in the CFRP plate ends, regardless their distributions. Furthermore, the loading test on the cantilevered steel plate with bonded CFRP plate was conducted. Debonding strength from the test results was approximately evaluated with principal stress in the adhesive, which is calculated from the estimated shear and normal stresses proposed in this paper.