Carbon Fiber Reinforced Concrete Static Loading Performance Study

Recently, an advanced composite material named Carbon Fiber Reinforced Plastic (CFRP) has emerged as an alternative to traditional strengthening materials. The existing reinforced concrete structures can be strengthened by externally bonded CFRP to improve their mechanical performances. Many advantages such as lightweight, non-corrosive, simple construction, and high tensile strength make it widely used in strengthening field. In this paper, ninety-five single-lap shear test specimens were used to study the ultimate bond load. The effects of concrete strength, bond length, bond width, and the number of plies of Carbon Fiber Sheets (stiffness of CFS) were taken into consideration, including various adhesive resins. Using statistical regress method, a calculating recommendation for determining the ultimate load is presented. Additionally, thirty-eight shear test specimens with lateral CFS for anchoring were used to study the improvement of the ultimate bond load between CFS and concrete. In this paper, twenty-one simply supported beams, strengthened by CFS, were tested. The influence factors of concrete strength, reinforcement ratio and the number of plies of CFS etc. were taken into consideration. Experimental results indicate that the beams without any anchorage would tend to collapse by a sudden catastrophic failure, characterized by plate debonding; By using anchorage system, this sudden debonding failure can be avoided; CFS can evidently increase the flexural load-bearing capacity of the beams. The plate debonding failure is governed mainly by the ultimate bond load between CFS and concrete in this test. And the method for calculating the normal section flexural load-bearing capacity is proposed, which can meet the Chinese engineering requirements. Additionally, the stiffness and crack performance of the above tested beams are analyzed. In this paper, the use of CFS for strengthening the initially loaded beams was also investigated. Two reinforced beams were initially loaded to a predetennined level of the ultimate capacity and then repaired by CFS. The load-bearing characteristics of the repaired beams are discussed and the calculating method for the flexural ultimate load is also proposed. Furthermore, in order to overcome the initially loaded effect or improve crack performance, the concrete beams strengthened with prestressed CFS were tested in several beams, and the experimental results of the strengthened beams are presented. Finally, a processing system and technology for prestressing CFS is introduced. In order to study the shear load-bearing capacity of RC beams strengthened by CFS, eleven simply supported beams strengthened by CFS strips were tested. And the method for calculating the shear load-bearing capacity is proposed. The effective anchorage systems were proposed when the CFS was used for shear strengthening of T-section RC beams. In order to study the fire resistance capacity of RC beams strengthened by CFS, the fire resistance test for strengthened beam was experimentized. The design method for fire resistance was proposed at last. Finally, the design strength for CFS is proposed by using the reliability analysis method. And the method for calculating the normal section flexural load-bearing capacity can meet the reliability requirements.