​Case Study: Salt Lake City's Suspended Skyscraper

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Meeting a tall order

There’s more than meets the eye at 111 Main, Salt Lake City’s most prominent new office building. Behind the glass facade, a feat of structural engineering allowed the 25-story tower to rise on a surprisingly complex site. As with any building in a seismic zone, we designed the 387-foot-tall building to withstand earthquakes. The bigger challenge was to accommodate an important new neighbor: the Eccles Theater, a 2,500-seat performing arts center, planned for the adjacent lot.​

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Double duty

To meet the requirements for both buildings, we designed a portion of the tower to be suspended above the four-story theater. All of this had to be delivered on a demanding schedule: the office tower and the theater below would be built at the same time.

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Hoisting the high-rise

An innovative engineering system called a “hat truss” suspends the tower above the theater. This structural steel framework weighs 1,870 tons. To support the tower’s perimeter columns, the truss extends outward 45 feet from the tower’s core walls. These walls are built of reinforced concrete, making the tower resistant to gravity, wind, and seismic forces.

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Open spaces

We used a conventional long-span, composite-steel floor framing construction to connect the core walls to the perimeter steel frame and suspended columns. The design brings big advantages: vast, column-free floor plates, as well as a dramatic lobby that can accommodate spillover crowds from the theater next door.

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This innovative engineering solution enabled the project teams for 111 Main and Eccles Theater to work independently toward a shared goal. With parallel construction timeframes, the design and construction of the two buildings continued at a rapid pace.

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Tour de force

111 Main was completed in 2016. As one of the city’s most prominent new buildings, it elevates the quality of architecture in Salt Lake City’s evolving downtown corridor. Together with the performing arts center, it’s already seen as a catalyst to revitalize downtown. “It is clear Salt Lake City has a new icon,” said Mayor Jackie Biskupski at the dedication ceremony for 111 Main, “and this is just the beginning.”