Sloped RBS Moment Connections at Roof Floor Subjected to Cyclic Loading: Analytical Investigation

Reduced beam section (RBS) steel moment connections are the prequalified connections in current design specifications and widely used in the US. Although RBS connection details are for general applications, they are not applicable for sloped beams at roof floors because the prequalified connections were developed based on the orthogonal beam–column conditions in a typical floor. A series of finite element analysis were conducted to investigate the effect of beam slope at roof floor on RBS connections. The results demonstrated that the connections at roof floor were vulnerable to fracture at the heel location when the beam was sloped down from the connections. But the stresses at the heel location were relatively small when the beam was sloping up. The downward beams developed plastic hinges accompanied by buckling, but the upward beams experienced only minor damage. Analysis results also indicated that the beam slope should not be more than 10° to adopt the prequalified connection details. The deformation at the heel location could be limited by introducing a rib plate at the connection and accordingly, the force demand at the connection could be effectively reduced.