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February 5, 2021

National finalist: Platinum award — Structural Systems
Magnusson Klemencic Associates

Photo by Jason O’Rear/Chase Center
Chase Center was built atop as much as 130 feet of fill, bay mud and weak soils.

Project: Chase Center
Client: Golden State Warriors

Chase Center is much more than a basketball arena and the new home of the Golden State Warriors. It is an urban, mixed-use complex that anchors San Francisco’s Mission Bay District — transforming the once deteriorating, uninspired, industrial landscape. The massive undertaking included designing a jewel box building housing an 18,000-seat arena, team headquarters, and practice facilities for the NBA team as the centerpiece to the project, including two 11-story office towers, a 950-car parking garage, 29 unique retail outlets, multiple public plazas and a future 13-story hotel.

While the shoreside Chase Center is not literally in the bay, the site was once part of the bay. It may look like solid, flat earth, but it is a varying 40-foot to 130-foot layer of fill, bay mud and weak soils sitting on top of steeply sloping bedrock. The bedrock drops 90 feet from one side of the site to the other. The waters of the bay are still there — only 5 feet below the ground’s surface. Yet, the development program required two levels of below-grade construction into the water.

This would be a difficult site in any city, but when you add in the seismic risk of San Francisco, the magnitude of the challenge is exponentially greater. The bay mud will also liquefy during significant earthquake events, requiring everything to be supported structurally, both vertically and horizontally. The project’s enormity further enhances complications — it covers the equivalent of eight downtown San Francisco-sized city blocks.

To conquer all of these challenges, Magnusson Klemencic Associates created a water-tight, concrete structural “boat” to hold back the water and contain all of the buildings in a single structure. The boat uses long compression piles to bedrock to support areas where the heavy building loads would make it sink and tension piles anchored in the bedrock to hold down other places where the building would be lifted out of the ground by the water force.

MKA’s multiple engineering innovations made this all possible, including integrating and creating the structural boat, graduated pile foundations, a utility “cocoon” system, and a single, comprehensive base structure with nine projecting concrete cores providing earthquake resistance. The firm also worked with the contractor using an unusual earthquake joint-elimination technique and a new super-truss roof system for the long spans that allowed a 90-by-60-foot “hole” at the center of the span to serve as a garage for the largest scoreboard in the NBA.


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