Experimental Study Of Reinforcement Concrete Frame Joints Strengthened With CFS

Joints are the most important parts in the Reinforcement Concrete (RC) frame structures. The RC frame would collapse if the joints failed. Especially for those joints which have little or no stirrups in their core areas. This paper mainly focuses on the rehabilitation of the RC frame joints with the Carbon Fiber Sheets (CFS) which had no stirrup in the joint cores.As a new strengthening material, the CFS has many excellent mechanical properties, such as high tension strength, light in weight, resisting corrosion, thin and flexible, etc. In recent years, it has been widely used in the rehabilitation of reinforced concrete structures. Many researchers and engineers have studied the CFS rehabilitation technique in the world. However, until now, most of researches focused on the studies of the CFS rehabilitation technique of the RC beams, columns and plates, while very little systematically studies on the RC frame joints. Basing on the experiments, this paper has done research on the CFS strengthening and the CFS-small steel frame strengthening of the RC frame joints. The following are summarizes of the experimental study and theoretical analysis:1. On the basis of the experiment of five full-scale RC frame joint specimens (one non-strengthened joint, two plane joints strengthened with the CFS and two quasi-space joints strengthened with the CFS-small steel frame) , this paper proposed the CFS strengthening method and the CFS-small steel frame strengthening method, the latter especially fits for the space frame joints. The failure modes, ultimate capacity, hysteretic behavior and ductility factor of theses joints have been researched. The experiment results show that by the strengthening way of this paper, the anti-seismic capacity of the joints could be significantly increased. Compared with the non-strengthened one, the ultimate capacity and the ductility of the strengthened joints have greatly increased. Typically, the CFS-small steel frame strengthening method results a remarkable strengthening effect. In a word, the CFS and the CFS-steel frame strengthening methods suggested by this paper are very effective and fit for the practical use.2. The force transfer mechanisms of the ordinary RC frame joints and the RC frame joints strengthened with the CFS and the CFS-small steel frame under the horizontal loads have been researched. Basing on the experiments of this paper and the achievements of the other researchers, two calculation formulas have been proposed to evaluate the shear strength...