Seismic shear behavior of new high-strength reinforced concrete column and steel beam (New RCS) joints

Abstract

New high-strength reinforced concrete column and steel beam (New RCS) joints were developed in this research. Two-way, through-beam New RCS joint details with beams concentrically or eccentrically connected to the joint were proposed. The beam in one direction was continuous through the joint (continuous beam). The beam in the other direction was connected to the continuous beam by complete joint penetration (CJP) groove welds. Five-spiral reinforcement was used for joint transverse reinforcement. A method to calculate the amount of five-spiral reinforcement was proposed considering the confinement effect from the face-bearing plates (FBPs). Doubler plates were used to strengthen the eccentric beam flanges with predrilled holes to allow the passage of column longitudinal reinforcement. A method was proposed for the design of the doubler plates. Large-scale New RCS joint specimens designed to fail in joint shear were tested. Test results showed that the proposed joint details and design methods effectively avoided failure in undesirable locations. All the specimens failed in joint shear but still reached high drift ratios. The eccentric joint specimens (IDEHS and ISEHS) exhibited peak joint shears higher than the concentric beam specimen (IHS). The 1994 ASCE and 2015 ASCE shear strength models produced conservative predictions of the peak joint shear and the joint shear at 0.5% joint shear deformation for all the specimens. The predictions by the 2015 ASCE method were more reasonable with less scatter than the 1994 ASCE method because the former recognizes the shear strength contribution from the outer joint panel even without the use of shear keys and allows a longer steel web in shear strength calculation.