Rehabilitation of earthquake damaged external RC beam-column joints

Post-earthquake inspections of damaged RC buildings have demonstrated that poorly detailed beam-column joints can suffer serious damage. The effectiveness of a rehabilitation method based on joint enlargement using prestressed steel angles to enhance the seismic behaviour of damaged external reinforced concrete beam-column joints was experimentally investigated. Three half scale external RC beam-column joints with seismic and non-seismic reinforcement details were tested before and after rehabilitation by applying lateral cyclic loading of increasing amplitudes. Tested specimens were comprised of one unit having seismic reinforcement detailing and two units having non-seismic reinforcement detailing. Two defects were considered for the non-seismic units, being the absence of transverse steel hoops and insufficient bond capacity of beam bottom steel reinforcing bars in the joint panel zone. The damaged specimens were rehabilitated by injecting epoxy grout into existing cracks and installing stiffened steel angles at the re-entrant corners of the beam-column joint, both above and below the beam, that were mounted and held in place using prestressed high tensile strength bars. The test results indicated that the seismic performance of the rehabilitated specimens, in terms of strength, stiffness and ductility were fully recovered with respect to the performance of the seismically detailed specimen in the initial loading.