Seismic Behavior of Exterior Beam-Column Connections with Plain Bars and Effects of Upgrade

Cyclic load tests on six reinforced concrete (RC) exterior beamcolumn subassemblages simulating joints of buildings constructed before the 1970s, with nonoptimal reinforcing details to resist earthquakes, are described. The exterior beam-column joints were reinforced by plain bars and lacked transverse reinforcement, and the longitudinal beam bars were poorly anchored. Two of them had inadequate beam top reinforcement. All of the beam-column joints were also tested after the upgrade, except one, which was upgraded and then tested for the first time. The proposed upgrade techniques were aimed at providing an effectual anchoring to the beam longitudinal bars and at increasing strength and stiffness of the beamcolumn joints. As expected, the performance of reference specimens (without upgrade) was found to be unsatisfactory in terms of lateral load capacity and stiffness. The improvement in the performance of the upgraded specimens is demonstrated