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January 27, 2020

National finalist: Gold award
Structural Systems

Magnusson Klemencic Associates

Photo provided by MKA
Amazon’s Spheres are the centerpiece of the 5.2 million-square-foot Amazon Urban Neighborhood project, which also includes three towers, retail and park space.

Project: Amazon Urban Neighborhood
Client: Amazon/NBBJ

The Amazon Urban Neighborhood encompasses six buildings on three blocks in downtown Seattle, transforming a district previously dominated by surface parking lots and low-rise cinder-block buildings.

The Amazon Urban Neighborhood offers 5.2 million square feet of structured floor area and includes three 38-story towers, street level retail, outdoor park areas, and the centerpiece of the project: the iconic Amazon Spheres.

As the project’s structural, wind and seismic engineering firm, Magnusson Klemencic Associates made a number of profession-leading structural engineering contributions.

Tackling the challenge of Seattle’s high seismicity, MKA used new performance-based seismic design (PBSD) techniques with the design of the three towers, improving upon the standard building code requirements and providing improved earthquake performance and better distribution of structural building materials throughout the building. The technique uses multiple “real” earthquake records (seven for the Amazon towers) instead of the simplified building-code-specified, single-design earthquake loading. This is the largest building project in the world to use PBSD.

Also for the three towers, MKA created a high-performance core that resists 100% of the wind and earthquake loads without requiring the participation of any exterior bracing, columns or spandrel beams. This allows for a near doubling of exterior column spacing (30 feet at the perimeter vs. 15-20 feet in comparable buildings in the region), allowing for better views and more space-planning freedom.

Perhaps most recognizable on the new Amazon campus are its Spheres, comprising three interlocking spherical structures. MKA invented a new structural sphere system, rejecting the repetitive straight-line geometry of traditional sphere structural systems.

MKA worked with architecture firm NBBJ to create a new sphere structural system inspired by the design of the traditional soccer ball. The team explored more than 100 designs within a repeating pentagon shape, settling on the “catalan” for its aesthetics, structural abilities, and constructability by the project team.

The resulting system is a self-supporting, 130-foot clear span with no interior columns that is completely independent from the interior concrete structure. Highly detailed 3D computer models utilizing custom software shared by the entire design and construction team streamlined design, detailing and fabrication, resulting in fabrication tolerances of just 1/32 inch.


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