Seismic Behavior of Reduced Beam Section Moment Connections to Deep Columns

An analytical study was conducted to investigate the seismic behavior of reduced beam section (RBS) moment connections to a deep wide flange column. Calibrated three-dimensional finite element models of RBS connections in perimeter special moment resisting frames with deep columns were used to perform parametric studies under inelastic monotonic and cyclic loading. The parameters in the study included: beam-to-column connection type, column section, composite floor slab, panel zone strength, and beam web slenderness. The results from the parametric study show that a composite floor slab provides restraint to the top flange of the beams, reducing the magnitude of beam top and bottom flange lateral movement in the RBS, column twist, and strength degradation due to beam instability in the RBS. The effect of beam web slenderness contributing to an increase in the lateral movement of the beam flange in the RBS and column flange is significantly reduced when a composite floor slab is present. A weaker panel zone results in higher potential for ductile fracture in the connection region. An RBS connection to a deep column is shown to have less potential for ductile fracture in the connection region than a welded unreinforced flange connection. The potential for fracture is increased in RBS connections when the column section properties are reduced, leading to larger stress and strain.