Research Of Interfacial Stresses Of FRP Strengthened Flexural Members

In recent years, with the rapid development of construction industry, more and more old buildings are needed to be strengthened due to the damage. Fiberreinforced-polymer has advantages over the traditional strengthening materials. Due to the superior mechanical and physical properties aswell as the flexibility, FRP is applied to strength the members of structural buildings and bridges. For the structural members strengthened by FRP, debonding failure is the main failure mode. This debonding failure is brittle and the strength advantage of FRP is not fully ustilized. Many researchers have done theoretical and experimental studies on debonding failure and have made some progress. However, the failure mechanism still needs to be further investigated. By theoretical deduction and numerical experimental analysis, present study obtains the following research contents:(1) Theoretical analysis is conducted to investigate the interfacial stresses of the FRP strengthened beams. Based on the compatibility of deformation and Timoshenko beam theory, the governing equations are successfully established. The application of Timoshenko beam theory takes the effect of adherend shear deformation into consideration, which makes present solution more rigorous and reliable. During the procedure of weight residual method, different forms of trial function are compared to determine the superior form. The general expressions of interfacial stresses are then obtained.(2) A CFRP plate strengthened simply-supported beam is selected as illustrative example. By MATLAB, the values of peak interfacial shear and normal stresses are caluated. The comparison between present solution and the existing solutions shows the effect of adherend shear deformation and the accuracy of present solution. By parametric study, the parameters that are critical to the interfacial stresses are determined.(3) Numerical experimental analysis of CFRP strengthened RC beams is conducted. Firstly, the effect of adherend shear deformation and the accuracy of present solution is futher proven by the finite element analysis. Then, a specific finite element analysis is given to investigate a nonuniform and/or a discontinuous adhesive layer. The corresponding effects of the geometry size and location on the interfacial stress and the stress distribution of adhesive layer are then demonstrated.