181 Fremont Street A State-of-the-Art Collaboration of Structural Design, Fabrication and Erection Methodology [CS6]

This session focuses on the design and construction of an all-steel, 56-story mixed use tower in San Francisco, CA. The superstructure includes a lateral system of steel moment frames and external mega braces. Arup's resilience-based design approach, following the REDi Rating System guidelines, extended the minimum code life-safety considerations to the ability to maintain occupancy after a 500 year earthquake. It is the first REDi-rated building in the world, having achieved a Gold designation through an independent peer review process. The Herrick Corporation provided design-assist, fabrication, and erection, with erection engineering support provided by Degenkolb Engineers. The project includes a number of structural steel innovations including 18-story mega braces that have both BRB elements and dampers to accommodate the demands from both EQ and wind loads for human comfort in the residential units. Also, to limit loads to the system in the MCE event, a unique uplifting element was designed into the base of the corner mega-columns. Steel erection complexities necessitated the implementation of temporary falsework to facilitate the construction of story-deep transfer trusses, design of critical lifting lugs and erection aids, and the development of an analytical ""dashboard"" that predicted the building's behavior during erection to help set columns. This session will provide an overview of this complex project, focusing on the structural design, fabrication, and erection of this state-of-the-art structural system.

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