Not the Ryan it was the Chicago Skyway.
A scary ride on good days.
http://en.wikipedia.org/wiki/Chicago_Skyway
Chicago required the Skyway to remain open during construction, engineers had to construct temporary bridge piers that would bear the load of the bridge and its traffic while new piers were built. Once ready, the bridge was lifted up onto the temporary piers using 600 ton hydraulic jacks, the old piers were removed, and new ones were built. Crews also devised innovative methods for replacing the bridge’s structural steel, replacing steel members one at a time. This process involved installing hydraulic chords around the component to be replaced. The bridge load was then transferred to the hydraulic chord, the steel member was removed and a new steel member was then installed.
Right ~ the Skyway. But from Chicago Roads.com try this honey: “
REBUILDING THE RYAN: As early as 1963, cracks began to form in the local lanes under the pressure of traffic that measured 180,000 vehicles per day (AADT), or 50% more than had been forecast. By the late 1960s, with traffic exceeding 210,000 vehicles per day, the steel reinforcement rods in the pavement had begun to fail. Poor drainage—particularly from the deicing salts used in the winter months—also was cited as a culprit.”