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Based on double shear test, to study the performance of FRP and concrete bonding interface as the FRP sheet bond length is relatively short (hereinafter referred to as short bond). This paper mainly focuses on the research of interface failure modes, ultimate bearing capacity, interface fracture energy, the development and distribution regularity of strain and stress. Therefore, the interface bond slip relationship curve is obtained through differential operation and data regression analysis on FRP strain values which was gained from test. Results show that: (1) under the condition of short-bonding, damage form of FRP and concrete bonding interface is shear failure which caused sudden destruction to the inner of concrete block; (2) The ultimate bearing capacity, interface fracture energy and maximum shear stress increase with the improvement of concrete strength; (3) the interface shear stress - slip curve is obviously featured as nonlinear, composed of rising and falling, basically presents as a parabolic shape.

The RC beams strengthened by externally bonded steel plates are regarded as composite beams which consist of steel plates and reinforced concrete with bond-slip. Based on the deformation compatibility relationship between steel plates and reinforced concrete, the constitutive relationship which can reflect the mechanical properties of steel plates and reinforced concrete and the bond-slip constitutive law, a nonlinear differential equation for the beam, expressed in the form of the tensile force of steel plates, is derived. A nonlinear analytical solution under the double concentrated load of the RC beams strengthened by externally bonded steel plates is obtained. By which a coordination coefficient in the form of the characteristic value of the beam is deduced. By using the coordination coefficient, a practical nonlinear analysis method, which can exactly reflect the bearing capacity and deformation of the beam is established.