Seismic Load Tests on Interior and Exterior Beam-Column Joints with Substandard Reinforcing Details

Simulated seismic load tests on reinforced concrete one-way interior and exterior beamcolumn joints with substandard reinforcing details typical of buildings constructed before the 1970s are described. The interior beam-column joint cores lacked transverse reinforcement and the longitudinal bars passing through the joint core were poorly anchored. Some of the beam-column joint units were also tested after retrofitting by jacketing with new reinforced concrete. The limited ductility available from interior beam-column joints with the substandard details, the improved ductility available from the retrofitted joints, and a means of seismic assessment of interior beam-column joints without transverse reinforcement are discussed. The exterior beam-column joint units contained very little transverse reinforcement in the members and in the joint core. In one beam-column joint unit the beam bar hooks were not bent into the joint core. That is, the hooks at the ends of the top bars were bent up and the hooks at the ends of the bottom bars were bent down. This anchorage detail was common in many older buildings constructed before the 1970s. In the other beam-column joint unit the hooks at the ends of the bars were bent into the joint core as in current practice. The improvement in performance of the joint with beam bars anchored according to current practice is demonstrated.