"Edge Effects in Retrofitting of Concrete Beams Using Fiber Reinforced Polymer Stripes—Closed-Form, High-Order Theory Approach"

A closed-form high-order analytical approach for analysis of concrete beams strengthened with externally bonded fiber-reinforced polymer (FRP) stripes, on the tensile faces of the RC beam in positive and negative bending moment regions, is presented. The mode is based on equilibrium and compatibility requirements in and between all constituents of the strengthened beam, i.e. the concrete beam, the FRP stripe, the adhesive layers and the interfaces between the various parts. The governing equations of the mathematical model of the strengthened beam are derived and an analytically closed-form solution is determined. A numerical example of a typical continuous reinforced concrete beam strengthened with externally bonded FRP stripes is discussed with emphasis on the shear and transverse normal (peeling) stress concentrations at the adhesive-concrete and adhesive-FRP interfaces at the edges of the FRP stripes. Results concerning the edge stresses at three characteristic locations that have been determined using the closed-form high-order model are discussed. In the sequel a summary, conclusions, and recommendations for the design of the strengthened beam are presented.