Interface Shear Stress: A New Design Criterion for Plate Debonding

This paper critically assesses the applicability and reliability of existing analytical techniques to predict and/or prevent brittle plate debonding failure that occurs in reinforced concrete (RC) beams strengthened with externally bonded steel or fiberreinforced-polymer composite plates. The experimental results, available to date in literature, have been very carefully reviewed and analyzed for this purpose. A new approach, very different from existing methods, and based on the interface shear stress obtained form elastic analysis of RC beam cross section and the fundamentals of force transfer mechanism in a bonded joint, is presented to predict the premature plate debonding phenomenon. The paper identifies important structural, material, and force parameters that influence this critical interface shear stress value between the bonded plate and concrete. The relations between these parameters and interface shear stress value are also examined and found to be consistent and logical to predict plate debonding at the plate cutoff end. The validity of this new design-oriented approach and scope for further research are also discussed.