Design by testing procedure for intermediate debonding in EBR FRP strengthened RC beams

Externally bonded (EB) Fiber-Reinforced-Polymer (FRP) sheets and laminates are widely employed for enhancing the bending capacity of reinforced concrete (RC) beams. However, the adhesion between FRP and concrete substrate is an issue of concern and generally controls the ultimate capacity of RC beams. Particularly, intermediate debonding phenomenon which begins from an intermediate point throughout the FRP-concrete interface is one of the most common and peculiar failure modes observed in RC beams externally strengthened in bending by bonded FRP.The present paper applies a well-established procedure for calibrating a design formula for determining the maximum axial strain developed in FRP at the onset of intermediate debonding failure. The procedure is based on the well-known design-by-testing approach based on the availability of a wide collection of experimental results.General behavioral observations are firstly derived by analyzing a large number of experimental results available in the scientific literature and collected by the authors. Such results are finally used for calibrating a design formula which looks after the key mechanical parameters controlling the bond behavior. The model uncertainties are handled through a consistent statistical procedure leading to a sound definition of the characteristic value of the relevant design quantities.

► The present paper is aimed at deriving a formula for intermediate debonding failure.
► Some general behavioral observations are firstly derived by previous studies.
► Experimental results are utilized for calibrating a design formula.
► A design-by-testing statistical procedure comply to the Eurocode is used.