Full-scale experimental testing of RC beam-column joints strengthened using CFRP ropes as external reinforcement

Abstract

Common reasons often impose the strengthening of elements of existing reinforced concrete structures designed according to various regulations including contemporary codes. Such reasons could be the change of the initial purpose of the structure, the need to increase the seismic capacity due to alteration of the seismic characterization of the region, the adding of an extra story on the top of the structure or just the need for increasing the seismic capacity of the structure. Τhe innovative material of carbon fiber ropes is used as externally applied reinforcement for the strengthening of reinforced concrete exterior beam-column connections and the efficiency of this technique is experimentally investigated. Eight full-scale exterior connection subassemblages are constructed and tested under increasing imposed cyclic deformations. Six of the specimens are strengthened by applying external X-shaped ropes at each side of the body of the joint and straight ropes at each side of the beam while two control specimens are tested without being strengthened. All ropes are placed into notches curved on the concrete surface. The hysteretic responses of the tested specimens are presented and compared to one another. Further, a damage index is calculated and used to evaluate the efficiency of the applied strengthening technique. The strengthened joints exhibited improved hysteretic response compared to the unstrengthened specimens in terms of maximum loads per loading step, stiffness, energy dissipation and damage index and it is deduced that the application of the carbon fiber ropes as external strengthening reinforcement has been proved to be an efficient strengthening technique.