ABSTRACT
Improved welding procedures used in combination with the reduced beam section (RBS) connection detail appear to perform much better in steel moment frames than details used prior to the 1994 Northridge, CA earthquake. As a result, the likely failure mode for RBS moment frames is beam instability during very large (> 3%) inelastic drift excursions rather than weld fracture at relatively small drifts (< 1.5%). The question now becomes what is an acceptable drift limit for design-level earthquakes? To address this question, one must consider the consequences of beam instability. This paper presents results from two tests of full-scale interior moment frame subassemblies with composite slabs. Measurements and observations from large post-buckling drift excursions are discussed.
