The Effect of Powder Actuated Fasteners on the Seismic Performance of Protected Zones in Steel Moment Frames

Abstract

Steel moment resisting frames rely on large inelastic strains in the beam plastic hinge region to dissipate seismic energy during an earthquake and protect the building against collapse. To limit the potential for premature fracture and because of a lack of test data, fasteners, attachments and defects are prohibited in the plastic hinge region, also referred to as the protected zone in the AISC Seismic Provisions. However, unauthorized attachments and defects occur in many buildings in practice. A set of twelve full-scale moment connection tests were conducted to explore the effect of powder actuated fasteners (PAF) and puddle welds on the seismic performance of steel moment connections. Both reduced beam section and extended end plate connections were tested with W24x62 and W36x150 beams. Five specimens included PAF or puddle welds representing typical steel deck attachment to the top flange of the beam. Three of the specimens included PAF in a grid over the top and bottom flange and on the web. All twelve specimens passed the qualification criteria for special moment resisting frames (SMRF) in the AISC Seismic Provisions as they were subjected to a cyclic displacement protocol up to 4% story drift while retaining 80% of their nominal plastic moment capacity. This suggests that moment connections with PAF and puddle welds within the bounds of what was tested, will produce ductile SMRF type seismic performance. Furthermore, PAF and puddle welds were found to have negligible effect on cyclic envelope, moment capacity, energy dissipation and strength degradation prior to fracture.