A nonlinear model for predicting intermediate crack-induced debonding in FRP-retrofitted beams in flexure

A nonlinear analytical model is presented and used to determine the interfacial shear and normal stresses at the FRP/concrete interface for RC beams externally strengthened with CFRP sheets. The computed stresses can be used to predict intermediate crack-induced debonding near the section of maximum moment. The model is based on composite beam theory with partial slip at the FRP-concrete interface permitted. Nonlinearity in the retrofitted beam is accounted for via consideration of the full moment-strain response of the unretrofitted beam. For model validation, the computed longitudinal strain along the laminate and the debonding load for a number of tested beams are compared with their corresponding experimental values. Furthermore, the shear and normal stresses distribution were also predicted. The theoretical predicted delamination load is in good agreement with the experimental results. The model yielded a reasonable theoretical load for beams with anchors and as predicted using ACI (08) method.