Allowable tensile strain of FRP in strengthening RC beam

Failure of externally bonded Fiber Reinforced Polymer (FRP) strengthened beam often occurs through debonding of the FRP from the concrete substrate. This failure type can be effectively avoided by restricting the tensile strain in the FRP. This paper provides a review of the progress achieved in this area regarding the design formula for the allowable tensile strain in the FRP. It is shown that the allowable tensile strain of the FRP is related to the stiffness of FRP and the strength of the concrete substrate. Chinese present design code leads to unsafe design when the concrete strength of the substrate is low, therefore it is necessary to improve the present design formula.