Critical Review of Plate Anchorage Stresses in Premature Debonding Failures of Plate Bonded Reinforced Concrete Beams

One of the major disadvantages of the plate bonding technology is the premature and brittle debonding failure of the bonded plate. It has been assumed, quite logically, that the stress concentration at the plate end is the primary cause of such premature plate debonding failure. However, there is no direct evidence of the validity of these stresses agree with the experimental data or not. Also there is concern if they can form the basis and criteria for the design and prevention of debonding failures. This paper presents a critical analysis of the calculated peak shear and normal stress values at the plate end using Roberts' approximate model, and derived from a wide range of published data involving steel, glass fiber reinforced polymer (GFRP) and carbon fiber reinforced polymer (CFRP) plates. It is shown that these calculated stresses are far too high, and cover unacceptably wide range of values, without any consistent pattern of variation with the plate stiffness. It is clear that the peak stresses are influenced by other parameters which are not taken into account in the approximate model used in the calculations. The wide range of the peak stresses cannot form a reliable basis to explain or design the prevention of premature plate debonding failures.