Fracture of Extended Stiffened End-Plate Moment Connections with Built-Up Beams

In the United States, there are three configurations of end-plate moment connection that are allowed for use in seismic special moment frames, two of which have stiffened end-plates extended beyond the beam flanges. Currently, built-up beam and column shapes are permitted for use with all three connection configurations. A series of nine experiments was conducted on extended end-plate moment connections to understand how the use of built-up beam shapes affected their fracture resistance and applicability for use in seismic applications. The beams, which were between 24 in. And 44 in. Deep, were either hot rolled beam shapes (four specimens), or built-up using plate and bar stock typical of-metal buildings (five specimens). Bolt patterns were varied from four bolts at each flange up to 12 bolts at each flange. The typical failure mode was fracture of the beam flange initiating at the toe of the end-plate stiffener, but a significant difference in deformation capacity was observed between specimens with hot-rolled and built-up beam shapes. When subjected to the AISC 341 SMF qualification displacement protocol, specimens with built-up beams failed at story drift ratios between 1.3% to 2.9% while specimens with hot-rolled beams survived through multiple cycles at 4% to 5% story drift ratio. Possible sources of the difference were investigated. Based on the findings, it is recommended that built-up beam sections not be used in extended stiffened end-plate moment connections for high seismic applications.