Concrete cover rip-off of R/C beams strengthened with FRP composites

In this paper the authors consider four FRP strengthened R/C beams brought to failure for concrete cover rip-off under uniform load conditions. Based on the available experimental results, a comparative study of different models for crack spacing evaluation is presented, accounting the influence of the FRP strengthening on the crack pattern development and stabilization. Among the considered models, the authors select a simple and efficient expression suitable to be proposed as a design tool. Thanks to the selected crack spacing expression, the authors work out a simple model that can predict the rip-off failure load of R/C beams externally strengthened with FRP with an acceptable accuracy. The model is calibrated making use of the four available experimental beams and is validated accounting for 23 experimental beams derived from the literature.