850-ft-tall Rainier Square Tower Tops Out in only 10 Months

Speedcore is living up to its name. The innovative concrete-filled composite steel plate shear wall (CF-CPSW) core system is being implemented on the Rainier Square Tower project in the heart of downtown Seattle. Structural steel framing for the 850-ft-tall high-rise topped out this week after being erected in only 10 months, approximately eight months faster than what would be expected if the building had been designed with a typical concrete core.

The building was designed by architect NBBJ and structural engineer Magnusson Klemencic Associates (MKA), with steel fabricated by Supreme Steel (an AISC member and certified fabricator). Once completed, it will house luxury apartments, offices, and retail space above six levels of below-grade parking.

The SpeedCore system, also developed by MKA (whose office is located in similarly named Rainier Tower, the building at left in the above photo), employs sandwich panels using steel plates filled with concrete. Cross-connecting tie rods hold the plates in place, supporting the wall panel before the concrete is poured, and the panels can support up to four floors of steel floor and metal decking even before the concrete is pumped in. What makes it come together so quickly is the elimination of the complex and time-consuming process required for a reinforced concrete core: setting formwork, installing reinforcing steel, placing embedded plates, installing sleeves and block-outs, and placing and curing concrete for each level.

In addition to speed, general contractor Lease Crutcher Lewis noted that the system also brings advantages in terms of safety, explaining that it remediates the danger of overhead work for ironworkers, which is constant as steel is typically intentionally placed behind the concrete wall pours in a concrete core structure.

While the CF-CPSW concept isn’t new—it has been used extensively for nuclear power facilities worldwide thanks to its impact- and blast-resistant qualities—Rainier Square Tower is the first use of SpeedCore in high-rise construction. And it won’t be the last. Thanks to the project’s success, MKA is designing five new high-rise buildings in California that will implement the system.

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