Thornton Tomasetti, Chicago
At 814 feet (248 meters), 110 North Wacker Drive is the tallest commercial office tower to rise in Chicago in more than 30 years. Built on a sliver of land bounded by Wacker Drive to the east and the Chicago River to the west, the 59-story tower was the product of architectural creativity and engineering ingenuity.
The project site’s trapezoidal shape meant a customized floor plate would be needed. To be appealing to tenants, the team designed long-span, column-free perimeter office bays within the narrow site, leaving little available space for an interior structural core. The composite concrete core and structural steel outrigger system efficiently minimizes the base width of the interior concrete core to just 29’9” at the narrowest section by engaging the perimeter building structure to resist lateral loads.
To maximize space for a new Riverwalk plaza, a system of dramatically sloped columns are clustered together and supported at three touchpoints along the river. These tall, slender supports are a distinctive architectural feature, engineered to gather the load from 54 floors overhead and precisely redirect it to the highest-capacity caissons used in Chicago. All of these structural solutions happen above a site with complex existing conditions to address: a previous low-rise building on deep foundations; a river wall with tie-backs deep into the site; elevated city bridges flanking the site on three sides; and below-site municipal utilities. The transformative strategy for how a structural system was developed that was capable of unlocking the full potential of the site to create a distinctive tower is discussed, as well as its impact to the skyline along the river’s edge.