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Fracture Mechanics Approaches to Debonding Behavior of Reinforced Concrete Members with Externally-bonded Fiber Reinforced Polymer Laminates

SYNOPSIS: Externally-bonded fiber reinforced polymer (FRP) laminates are commonly used to strengthen or repair reinforced concrete members. The behavior of strengthened members is influenced not only by the properties of reinforced concrete and FRP laminates but also by their interface properties such as bond strength. Conventional strength based approaches lack the accuracy required to predict the interface behavior because they do not account for energy release during debonding. A fracture mechanics approach can provide a better alternative because it can account for post-cracking behavior, debonding propagation, and flaws and defects at the interface and within the materials. This paper presents a review on recent fracture mechanics approaches used to understand the debonding behavior of reinforced concrete members with externally-bonded FRP laminates. With a brief description of failure modes of FRP-strengthened beams, the methodology and limitations of strength based models of debonding are summarized and discussed. As the debonding of FRP from beams can be categorized as Mode-I, Mode-II, or Mixed Mode, test methods to attain the critical energy release rate of the FRP-concrete interfaces in specific modes are also presented. Analytical and numerical fracture mechanics based models are reviewed with respect to fracture energy and energy calculation methods.