SEISMIC DESIGN AND BEHAVIOR OF EXTERNAL REINFORCED CONCRETE BEAM-COLUMN JOINTS USING 500E GRADE STEEL REINFORCING

摘要

Four external reinforced concrete beam-column sub-assemblages were tested under pseudoseismic cyclic loading. The approximately 2/3 scale units incorporated the new Grade 500E reinforcing steel as the beam bars. Two different forms of beam bar anchorage were tested, the normal 90-degree "standard hook" and the continuous U-bar detail. In all units the farthest point of the beam bar anchorage was positioned at the minimum limit prescribed in the NZ Concrete Standard (NZS3101), namely 3/4 of the column depth from the inner column face. All 4 units formed plastic hinges in the beam and joint degradation was minor. Failure occurred at drift ratios between 4 and 6% (approximate ductility factors of between 4 and 6) predominantly due to buckling of the beam bars in the plastic hinge zone. The stiffness of these units was significantly less than similar units reinforced with 300E Grade reinforcing or the recently replaced 430 Mpa reinforcement. The decreased stiffness will cause higher lateral drifts during large earthquakes, than those anticipated in current Standards.