Aug 2011

Effect of Fasteners and Defects in the Protected Zone on the Performance of Moment Frames

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This research is investigating the effect of fasteners and defects applied in the protected zone on the ductility, low cycle fatigue performance, and inelastic rotation capacity of steel beam-to-column moment frame connections.

Special moment resisting frames (SMRF) depend on large inelastic strains in the beam-to-column connections to dissipate seismic energy and protect buildings from collapse.  The ANSI / AISC 341-10 Seismic Provisions for Structural Steel Buildings  define the ends of the beams in a SMRF as protected zones at the locations where large inelastic strains are expected.  In this region AISC 341 prohibits any decking attachments that penetrate the beam flange and any welded, bolted, screwed, or shot-in attachments for other purposes.

The restriction on fasteners in the protected zone creates issues in construction due to the difficulty in communicating these restrictions to all subcontractors and future users of the building.  Common unapproved attachments that have been identified are the attachment of steel deck to the beam top flange, attachment of cold-formed steel wall track to the underside of the beam, attachments for mechanical / electrical systems, and others.

A testing program was conducted that uses a limited number of test specimens to represent a wide range of connection types and configuration parameters.  The first phase of the research involves full-scale beam-to-column connection tests.  The second phase of the research used smaller coupon specimens to represent the flange undergoing local buckling.

Test Setup at the Thomas M. Murray Structural Engineering Laboratory

Full-Scale Beam-to-Column Moment Connection with Powder Actuated Fasteners Applied to the Flange Demonstrating Significant Ductility and Deformation Capacity

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Watkins, C.E., Toellner, B., Laknejadi, K., and Eatherton, M.R. (2013) “Effect of Powder Actuated Fasteners on the Seismic Performance of Steel Moment Frame Connections” Proceedings of the 2013 ASCE Structures Congress, March 2-4, 2013 Chicago, Illinois.

Eatherton, M.R., Toellner, B.W., Watkins, C.E., and Abbas, E. (2013) The Effect of Powder Actuated Fasteners on the Seismic Performance of Protected Zones in Steel Moment Frames, Virginia Tech, SEM Report Series, Report No. CE/VPI-ST-13/05

Watkins, C.E. (2013) Developing a Full-Scale Test Setup to Study the Effects of Fasteners in the Protected Zone of Steel Moment Frames, M.S. Report, Virginia Tech

Toellner, B.W. (2013) Evaluating the Effect of Decking Fasteners on the Seismic Behavior of Steel Moment Frame Plastic Hinge Regions, M.S. Thesis, Virginia Tech