Analytical models based on the compatibility of deformations and equilibrium of forces are presented to predict the stresses and deformations in concrete beams strengthened with fiber composite plates epoxy-bonded to the tension face of the beams. The models are given for beams having rectangular and T cross sections. A parametric study is conducted to investigate the effects of design variables, such as plate area, plate stiffness and strength, concrete compressive strength, and steel reinforcement ratio. The moment versus curvature diagrams for various combinations of these variables are plotted and compared. The results indicate that bonding composite plate to a concrete beam can increase the stiffness, yield moment, and flexural strength of the beam. The method is particularly effective for beams with a relatively low steel reinforcement ratio.

Although strengthening by bonded steel plates, where adhesive is used to bond the steel plates to the structural members, has been established for more than two decades, it was not until recently that this strengthening technique has been used in Singapore. A number of reinforced concrete structures have been successfully strengthened using this technique over the last three years. This paper describes this strengthening technique with particular reference to the material selection and design considerations, as well as the strengthening and construction methodologies. A case study on one of the structures strengthened is also presented. The structural members strengthened include bonding of steel plates to beams to increase flexural as well as shear capacities and encasing columns to prevent buckling and increased load carrying capacity.

In this paper, a closed-form solution is obtained for partially plated beams. Linear elastic behavior is assumed for beam, plate, and adhesive. The behavior of the adhesive is idealized using the Roberts and Haji-Kazemi model. A system of differential equations is obtained and finally solved by detecting the distribution of shearing stresses through the adhesive layer. All other beam resultants are obtained via equations of equilibrium. The approach has suggested a simple experimental device that enables the user to evaluate the stiffness parameters of the adhesive layer. Finally, the response of the model is compared with numerical solutions by finite element model and the experimental results obtained for flexural tests on partially plated beams. A good agreement is observed.

Extensive research has established that the provision of epoxy bonded steel plates as external reinforcement can be effective and efficient in enhancing the serviceability and ultimate strength of reinforced concrete beams. This plate bonding technique has many technical and practical advantages and provides an economic means of strengthening and rehabilitating damaged and/or deteriorated structures. There is, however, only limited data on the long term performance and durability of such strengthened beams. This paper presents the results of a comprehensive test program in which 21 steel plated reinforced concrete beams, both unloaded and loaded, were exposed to natural weathering for up to 12 years, without any maintenance, in an industrially polluted area. The main variables investigated include adhesive thickness, number of plates, and number and location of plate laps. The beams were examined in great detail after the exposure period; the extent of corrosion damage and the mechanisms of deterioration due to this exposure are critically evaluated and presented.

Repair and strengthening of concrete structures by external reinforcement with steel plates affords the manufacturer of concrete adhesives an attractive new and potentially large opportunity for his products. In this application, bond lines are generally thicker and environmental effects more pronounced than in more traditional uses of such adhesives. In plate bonding, the adhesive becomes an integral part of the reinforcement system and must be capable of transferring stresses without lasting hysteresis effects. High modulus epoxy adhesives with high heat deflection temperatures (HDT) have been shown to have the necessary creep resistance and shear strength. In plate bonding, the internal steel surface is not protected against corrosion by the alkalinity of concrete. Corrosion resistant primers were found either to lack bond strength at high temperature or to enhance a reaction between the freshly prepared metal surface and the hardener component of the epoxy adhesives, which led to the use of unprimed steel plates. Unfilled, low viscosity resins appear to have better barrier properties against corrosion than filled pastes. Treatment of freshly prepared steel surfaces with certain silanes appears to retard flash rust formation as claimed in the literature.