Seismic shear and flexural performance of new RCS joints with W-FDP, W-FBP, and small hoops

Abstract

New through-beam joint details were developed for New high-strength Reinforced Concrete and Steel beam (New RCS) special moment frames. The columns hadfy = 690 MPa andfc′ = 84 MPa. The new joint details enhanced the joint strength for the large force demand seen in high-rise buildings in regions of high seismicity and minimized the construction difficulty associated with conventional joint transverse reinforcement. The new joint details included Wide Flange Doubler Plates (W-FDPs), Wide Face Bearing Plates (W-FBPs), and small rectilinear hoops. Three large-scale beam-column joint specimens with the proposed design details were tested using lateral cyclic loading to examine their seismic shear and flexural performance. Test results showed that the W-FDPs were effective in preventing joint bearing failure. Using W-FDPs, FBPs, or W-FBPs, and small hoops effectively mobilized the joint shear strength. The 2015 ASCE model modified to consider the proposed details provided a conservative estimation of the joint shear strength of the specimen that failed in joint shear. Moreover, the model was successfully used to design specimens to prevent joint shear failure and to produce desired beam-hinging behavior that met the requirement of AISC 341 for beam-column connections of special moment frames. The beam eccentricity did not significantly affect the hysteretic behavior of the specimen up to the 4% drift ratio.