Special moment frames are one of two reinforced concrete seismic-force-resisting systems that are recognized for earthquake-resistant concrete buildings in regions of highest seismicity in the United States. This presentation began with a description of the characteristics of special moment frames, and outlined the main principles that govern their proportioning and detailing. It went on to describe the use of special moment frames in modern buildings, including their typical dimensions, as well as strength and drift limit requirements.
Given a preliminary design of the structural system, structural analysis is used to determine the lateral drifts and the force demands on critical components. The presenter reviewed the recommended modeling procedures, including recommendations for stiffness modeling of beams, columns, and beam-column joints. He then reviewed the design steps, for both required strength and detailing, using a logical set of steps that most engineers follow in designing a special moment frame. Where useful for understanding the design requirements, he also reviewed some of the background studies that were the basis for the building code requirements.
The presentation concluded by reviewing additional requirements, with emphasis on construction considerations, illustrated by several construction photographs. The presented material was derived largely from the NEHRP Seismic Design Technical Brief No. 1 (NIST GCR 8-917-1), and was updated to incorporate the latest requirements of ASCE 7-10 and ACI 318-11.
Session Length: 1.5 hours
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