Experimental Investigation of Damaged Exterior RC Beam- Column Joints Retrofittrd by FRP Jacketing

The efficiency of a seismic retrofit using externally bonded fiber - reinforced polymer composites on existing damaged reinforced concrete joints , designed prior to the introduction of modern standard seismic design code provisions in the mid - 1970s, are herein presented, based on experimental investigations on beam - column joint subassemblies . The experimental program comprises 8 external beam – column joint connection subassemblages tested in 2 phases; the first phase was the damaging phase and the second was aimed to the repairing the damaged joints . The joints had no beam - column joint transverse reinforcement and special stirrups in beam and column critical lengths . T hese Non - Seismically designed (NS) joints were damaged with different levels at the first phase of the experiment. In the second phase, the damaged joints were strengthened with externally bonded carbon - fibre - reinforced plastics (C - FRP) sheets. From the ob served responses the load carring capacity and stiffness of the pre - damaged strengthened joints were improved in moderate initial damages ( less than 1.5% drift ratio). Also, the use of CFRP sheets increased the capacity of energy dissipation of the rehabil itated beam – column specimens in comparison to as - built specimen. I t can be deduced that the technique of externally bonded retrofitting (EBR) using C - FRP sheets is efficient in moderately pre - damaged joints, i.e. the damage level s less than 1.5% drift rat io . This level is named as the repaire - ability level by using EBR strengthening method.