A Three-Parameter Elastic Foundation Model for Interface Stresses in Curved Beams Externally Strengthened by a Thin FRP Plate

Externally bonding of FRP plates or sheets has become a popular method for strengthening reinforced concrete structures. Stresses along the FRP-concrete interface are of great research interest because high interface stress concentration can lead to debonding along the FPR-concrete interface and premature failure of the structure. In this study, we develop an analytical solution of FRP-concrete interface stresses in a curved structural beam strengthened by a thin plate through externally bonding. Unlike existing studies in which the adhesive layer is modeled as a two-parameter elastic foundation, this study simulates the adhesive layer as a three-parameter elastic foundation by introducing an extra independent parameter, the deflection of the mid-plane of the adhesive layer. In this new model, the interface shear stress is assumed constant through the thickness of the adhesive layer; while the interface normal stresses along two adherend/adhesive interfaces are assumed different. The equilibrium equation of the adhesive layer, which is violated in two-parameter elastic foundation model, is satisfied by this new model. Closed-form solutions of interface stresses and beam forces are obtained and verified by finite element analysis.