Modular "sandwich" system should shave 2 percent off the job's original concrete-core plan.
Starting next August, the 58-story Rainier Square Tower in Seattle will be built using an innovative composite steel frame that will cost less and take 40 percent less time to complete.
Rainier Square's steel erector predicts superstructure work will take about one year—some nine months less than it would the old way. "We will erect this building, totally, in less time than it would have taken to cast a concrete core by itself," says Adam Jones, president of The Erection Co. Inc.
ENR's report, Rainier Square Tower's Composite Steel Frame Called a Game-Changer, details the way engineer Ron Klemencic's team is applying tall steel core design in earthquake prone areas.
The system uses two steel plates connected by steel spacing ties with the cavity between the plates filled with high-strength concrete.
The tall shear wall system was developed through a series of studies and advancements by Magnusson Klemencic Associates (MKA). "The system is an evolution of many years of our work with composite steel columns, steel plate shear walls, and performance-based seismic design," Jon Magnusson, senior principal at MKA, explained.
The system provides the strength, stiffness, safety and serviceability of a reinforced concrete core without the negatives of rebar congestion and complex formwork. In addition, using the system means the entire structure is built to the tight tolerances standard in steel construction, rather than the broader tolerances permitted in concrete construction. "It fundamentally changes the game," Klemencic said.