Date of Graduation

5-2025

Document Type

Thesis

Degree Name

Master of Science in Civil Engineering (MSCE)

Degree Level

Graduate

Department

Civil Engineering

Advisor/Mentor

Prinz, Gary S.

Committee Member

Murray, Cameron D.

Second Committee Member

Hale, W. Micah

Keywords

cyclic loading; moment-resisting frames; reduced beam section connection; skewed connections; structural engineering; structural testing

Abstract

Existing experimental reduced beam section (RBS) moment frame investigations, particularly those used for prequalification in AISC-358, consider orthogonally oriented beam-to-column connections. While the design commentary provided in AISC-358 references recent skewed SMF numerical studies and potential performance effects when a lateral beam skew is introduced, limited experimental studies have been performed to verify the numerical findings. This study presents an experimental investigation into the cyclic behavior of RBS special moment frames that have lateral skew at the beam-to-column connection and composite concrete slabs. In this study, a skewed composite double-sided RBS connection is tested, having beam bracing outside the RBS connection to contrast observed behavior with recent testing neglecting RBS bracing, as is allowed when a slab is present. The test specimen in this study considers a W24x131 column and two W24x76 beams connected at a 15-degree lateral skew angle. Experimental results show that the connection retained 80% of its plastic moment capacity during 4% drift, meeting AISC-358 prequalification requirements. A beam top-flange fracture was observed at 6% drift due to ultra-low cycle fatigue resulting from the repeated local buckling of the beam flange. Moderate column twisting, and minimal column flange yielding at the acute skew angle side of the connection were observed. Inelastic deformation was successfully localized to the RBS region and there were no signs of the connection weld fractures. Comparing results with previous testing neglecting beam bracing, lateral beam bracing within d/2 from the RBS is recommended for connections having beam skews greater than 10 degrees, even if a composite concrete slab is present.

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