Debonding- and Fatigue-Related Strain Limits for Externally Bonded FRP

Available guidance for mitigating debonding failure of externally bonded fiber reinforced polymer (FRP) composites applied to concrete is evaluated based on data obtained from large- and full-scale experimental programs. Current recommendations are inadequate to effectively mitigate intermediate crack-induced debonding in flexural members. An improved, although still simple to apply, equation for determining limiting FRP material properties to mitigate debonding is presented and evaluated. Additionally, the effect of fatigue loading on the debonding behavior of externally bonded FRP is not adequately addressed in practice. In the limited data presented, a degradation of bond behavior is observed even under fatigue loading conditions amounting to an FRP stress range of no more than 4% of the FRP capacity.