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SP-165 The ACI Technical Session "Repair and Strengthening with Adhesive Bonded Plates" was held in Washington, D C on March 15-16, 1992. The papers presented at the technical session and the additional papers included in this special publication provide the first comprehensive publication of information on this subject in the United States. The papers cover research, design, construction methods, and case histories. The research described includes not only theoretical analysis and short-term experimental programs but also test programs that involve long-term outdoor exposure. research in the use of fiber reinforced plastic plates instead of the more commonly used steel plates is also described. The design papers illustrate practical engineering approaches and include details of anchoring plates, effect of plate dimensions, adhesive performance, and temperature limitations. Construction methods described include preparation of the plates, application of adhesive, and installation of the plates. The case histories provide a broad and historical view of the use of adhesive bonded plates to strengthen buildings and civil engineering structures.

Although some test data are available on the behavior of reinforced concrete beams with bonded plates in shear, there is still considerable lack of information on the effectiveness of such plates in resisting shear forces. This paper presents the results of the first stage of a comprehensive study to evaluate the role and mechanism of strengthening in shear when bonded steel plates are used either at the tension face or in the webs. The major variable in this study was the shear span-effective depth ratio, which is the critical parameter for shear failures; two different geometries of web plates were used. The effect of these bonded plates on deformations, cracking, failure loads, and mode of failure are presented and discussed. Bonded plates at the tension face enhanced the flexural stiffness of the original beams which were weak in shear, but their influence in enhancing shear behavior was minimal. Bonded web plates, on the other hand, were very effective in upgrading the structural behavior in shear. However, the latter were unable to reach their full load capacity due to shear cracking in the unreinforced part of the webs and the consequent debonding of the web plates.

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.

The plate bonding technique has been known and established in Europe for more than 20 years. Up to the present time, however, it has only been used in some specific applications. This is mainly due to the lack of an integral system approach. The increasing demand for strengthening, repair, and rehabilitation measures, especially in the field of the maintenance of structures, and the seismic upgrading or the change in use of structures ask for structural reliability and cost effectiveness. Both can be met with a new system approach for the plate bonding technique focusing on the requirements of engineering based design fundamentals; increase in ductility and strength, provided with permanent pressure applied to the steel plate; safe and easy handling on jobsite with adequate application system; overall quality control and assurance; integration of other plate/strip materials; and extension of the system to other subground material (masonry, wood, steel). A new system for the end anchorage of the bonded steel plates has led to a pronounced increase in ductility of the overall structural system so that the stringent requirements for structural elements used in engineering design can be met in full. A new design procedure is in development, based on extensive laboratory tests and preliminary field tests, as well as on finite element calculations. The new design procedure is fully in length with current developments in reinforced concrete design.

The use of steel plates bonded with epoxy adhesives to reinforced concrete structures is a technique more than 25 years old. In this paper, the applications of using this technique for construction of new structural members and strengthening of existing members are reviewed. For the strengthening of reinforced concrete beams and columns, preloading prior to bonding of steel plates is studied to simulate the in situ strengthening process. For upgrading of columns, the transfer of stresses, lateral confinement of the concrete section, and failure modes are described. From the experiments carried out, it is concluded that strengthening with epoxy- bonded steel plates alone will not increase the ultimate strength of the column, though the stiffness in enhanced marginally. However, additional inclusion of lateral confinement plates improves its strength. In particular, the post-failure mode and post-failure strength may lead to highly potential applications. Test results of scale models are discussed and tentative design criteria recommended.