Ultimate response characteristics of steel RBS connections with jumbo sections (LAC23.C)

This paper examines the cyclic performance of reduced beam section (RBS) moment connections with larger member sizes than allowed in current seismic provisions. The study describes experimentally validated numerical assessments, including parametric investigations to evaluate the influence of RBS-to-column capacity ratio, as well as the RBS geometry and location, on the overall response. The numerical and test results offer detailed information on the behaviour of large RBS connections, such as their strength, ductility, and failure modes. It is shown that connections that consider sections beyond the code limits, by up to two times the weight or beam depth limits, developed a stable inelastic response characterized by beam flexural yielding and inelastic local buckling. Very large beam sections, beyond this limit, exhibit severe demands at the welds, increasing the susceptibility to fracture. The study recommends a deeper RBS cut for large sections with thick flanges, to about 66% of the total beam width, to promote extensive yielding at the RBS and reduce excessive strain demands at the beam-to-column welds.