Parametric investigation on the design of RBS moment connections with jumbo beams and columns

Abstract

Recent experiments demonstrated that reduced beam section moment connections with some of the largest hot-rolled beam and column shapes (jumbo shapes) may not have sufficient ductility for high seismic applications if designed according to current design procedures. A parametric computational study was performed to evaluate potential changes to the design procedures to enhance the ductility of these connections with jumbo shapes. First, three-dimensional finite element models were developed and calibrated to match cyclic experimental results including load vs displacement response, panel zone deformations, and deformed shape. The models were then used to conduct parametric studies with inelastic monotonic loading to examine the effect of design parameters including beam flange reinforcing fillet weld size, panel zone strength and doubler plate location on fracture potential. The results showed that the size of the reinforcing fillet weld on the underside of the bottom flange has a significant impact on the local stresses and strains at the location of fracture initiation in the tests and that larger size fillet welds should be used with jumbo beams to mitigate the concentration of inelastic strains. The results also showed that joints with higher panel zone strengths lead to lower fracture potential and that moving the column web doubler plate outwards to the edge of the flange is another effective strategy to reduce local strain concentrations. The absence of local buckling in jumbo sections eliminates the strength degradation that limits demands on the welds and needs to be taken into consideration in their design.