111 S. Wacker Drive
Cost: $275 million

The 52-story 111 S. Wacker Drive tower in Chicago's West Loop features more than 1,000,000 sq. ft. of office space.

Two major tenants have leased space, accounting firm Deloitte & Touche of the 12th through 28th floors and law firm Lord Bissell & Brooks of the 41st through 52nd levels.

The building also includes 4,000 sq. ft. of retail and 485 parking spaces.

The tower has a cable wall system from the street level to the third floor, thereby providing a transparent look to the ground level.

The cable wall features about 70 cables that span approximately 50 ft. from the plaza level to the third floor.

At 1-in.-thick, the cable is a smaller diameter member than aluminum or steel mullion and does not interrupt the glass facade.

Each cable is stressed to a specific design tension, depending on the location, span and wind loads. The tensioning stiffens the cables, permitting them to handle positive and negative wind loads.

As each cable was tensioned and force was applied to the cable, the building t both the plaza and third-floor levels deflected slightly due to the applied loads.

Timing the cable wall installation was important, because structural components had to be in place before tensioning could begin.

Below Grade Work

A solid foundation already existed more than two stories below ground.
Bell caissons and the four foundation walls supporting the U.S. Gypsum Building, the previous structure on the site, were sound.

But a problem was the caissons had supported the building that was only 20 stories and on a 45-degree angle.

The only way to reconcile the new geometry to that of the old building was to add caissons. Old and new caissons were tied together through the use of a giant mat slab that was laid in a monolithic pour.

The existing foundation walls were bermed with a high-density CA6 and rubble debris mix, and a solider pile and lagging system was installed around the foundation mat to reduce the cost of a retention system.

Above grade, floors three through 12 are a megatruss that supports the building's upper floors. The truss sits on massive 5 ft., 9 in.-dia. columns. Two pipe columns start at the second basemen level and are jointed at street level by four more pip columns that rise up to the third floor.

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