Kinky Boots

Seattle’s second tallest tower rises on steel plates, without rebar

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Seattle's second tallest tower rises on steel plates, without rebar. Side-by-side renderings of the Rainier Square Tower, left, with its core system exposed, right. (Left, courtesy Wright Runstad & Company, right, courtesy Magnusson Klemencic Associates)

Studies are underway for the eventual construction of the Rainier Square Tower in Seattle, which will eschew a traditional concrete-and-rebar core in favor of a new steel plate system. The mixed-use Rainier Square development’s tower will be Seattle’s second tallest, and the building’s modular core will be a proof-of-concept in the earthquake-prone city.

When AN first wrote about the NBBJ-designed and Wright Runstad & Company-developed Rainier Square Tower after its initial unveiling in 2015, comparisons were drawn between the building’s kinked shape and a high-heeled boot. The tower has grown from 795 feet tall to 850, but the distinctive massing and glassy facade have remained the same; the building’s slope is meant to preserve the view of the adjacent Rainier Tower, designed by Minoru Yamasaki.

The $570 million Rainier Square Tower will forgo a typical high-rise core, which wraps a steel frame around a concrete core that has been reinforced with steel rebar, and will instead use a modular system of steel plates sandwiched with concrete. A boundary system is set up to shape the core, and the cross-tied plates are moved into place, and then filled onsite.

(Courtesy Wright Runstad & Company)

The NBBJ-designed Rainier Square Tower will connect to Minoru Yamasaki’s Rainier Tower, without obscuring views of it. (Courtesy Wright Runstad & Company)

While the construction of a full-scale core mock-up began in October, the general contractor, Lease Crutcher Lewis, has estimated that this alternate method would mean that the superstructure, set to begin work this August, would only take a year to complete. If these claims are true, that’s nearly nine months sooner than a comparable tower of this size. And, as the construction schedule is shortened, Wright Runstad is expected to save 2 percent of its original $370 million building costs.

Structural engineer Ron Klemencic, CEO of Magnusson Klemencic Associates (MKA) is the system’s mastermind, and says that even with the increased construction speed and 58-story height, he’s confident that the tower will be able to withstand stress from wind sheering as well as seismic loads.

The Yamasaki-designed Rainier Tower, pictured before the surrounding buildings were demolished. (Penn State University Libraries/Flickr)

The Rainier Square development will not only include the tower, but also a cubic glass-clad hotel wedged between Rainier Tower and Rainier Square Tower. Yamasaki’s concrete tower, affectionately named “The Beaver” by Seattle locals for the way the building balloons up from a narrow base akin to a chewed log, is the only original building on the block that will remain.

If the engineering claims bear out and the new core system proves as easy to install as the contractors are expecting, Rainier Square Tower should be complete by April 2020.

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