BP Bridge, Rebar, Concrete Foundation Ramp, September 12, 2003
A view of the eastern approach ramp of the BP Bridge in Daley Bicentennial Plaza. Like most of Millennium Park, the BP Bridge is built upon an underground parking garage and this presented construction challenges. Most bridges sway a little, and most pedestrians can detect this motion, making a bridge seem unsafe, even if it's structurally sound. The cause of most movement in structures is the foundation, so to avoid this "motion perception," the engineers decided to drill through the existing parking garages into the bedrock, taking care not to damage the garages. The result is that the BP Bridge is a completely free-standing structure, independent of both the parking garages below it, and Columbus Drive which it spans.