Shoehorning a football field and seating bowl, complete with suites, into the horseshoe-shaped perimeter bay of a narrow venue built 80 years ago for track and field was enough to drive many toward distraction. Then, pile on the charge to gut and reconstruct the landmark sports facility in four to six months less than is comfortable and customary for National Football League stadiums. And top that with an unprecedented foray, at least on this scale in the U.S., into the largely alien world of three-dimensional computer modeling for design and fabrication of the job's 13,000-ton structural steel frame. It's not surprising that the push toward a "paperless" project at the $365-million makeover of Chicago's Soldier Field caused minor shock waves along the shores of Lake Michigan.
The structural engineer got the green light to create a 3-D model and share it with the steel fabricatorfor connection detailing and to drive its computer numerically controlled (CNC) fabrication equipmentbecause the steel structure and its complex radial geometry was on the critical path of the job's 20-month, fast-track schedule. The need to fit the new 61,500-seat bowl snugly into the historic colonnade structure, like a jumbo egg in a small egg cup, also drove the decision to use a 3-D approach. "If you can model it in 3-D, you can build it," says Joseph G. Burns, principal in charge for project structural engineer, the Chicago office of Thornton-Tomasetti Engineers. Click here to view diagram