Prediction of concrete cover separation failure for RC beams strengthened with CFRP strips

External bonding of fibre reinforced plastic (FRP) strips to reinforced concrete (RC) beams has been widely accepted as an effective method for strengthening. The ultimate flexural strength of strengthened RC beams can be improved significantly but it is often impaired by premature failure modes, such as concrete cover separation. The objective of this paper is to establish a simple and accurate design methodology to predict the load carrying capacity of a strengthened RC beam when concrete cover separation take., place. An analytical expression is developed taking into account the stress concentrations in concrete near the tension rebar closest to the cut off point of the FRP strip. The derivation of the expression involves two major steps: (i) determination of the tensile stress in the FRP strips assuming a full composite action; and (ii) obtaining the local stresses and comparison with the concrete strength. The predictions based on the present analytical model are compared to 58 experimental data from the literature and good agreement has been obtained. The expressions derived in this paper therefore have potential for application in the design of FRP-strengthened beams. (C) 2004 Elsevier Ltd. All rights reserved.