Bridge-Under-Bridge Design Allows Six Lanes of Traffic During Constructionon

global-business-north-america-magazine-Q12017.jpgGlobal Business North America goes inside the design of the award-winning Jane Addams Memorial Tollway (I-90) Fox River Bridge replacement in its First Quarter 2017 edition.

Two unusual design and construction methods were used to remove the aging six-lane twin bridge and build a new eight-lane twin bridge in the same location, while simultaneously keeping six lanes of traffic open. The substructure of the new bridge – footings and piers – was constructed underneath the existing bridge while it remained in service.

This unusual bridge-under-bridge design was possible because the beams used in the new bridge deck are much longer and deeper than the previous beams.

During construction of the new bridge, a gantry system was used instead of a large crane to place the massive 2,000-pound deck beams.The gantry system alleviated the need to position a large crane close to the rare forested fen located adjacent to the bridge.

Using longer, deeper beams reduced the number of piers and expansion joints in the bridge, which lowers future maintenance costs and increases its lifespan. Combined with the use of stainless steel deck reinforcement, the new bridge is expected to have a service life of between 75 to 100 years.

The Fox River Bridge received industry recognition from the American Council of Engineering Companies of Illinois in its annual Engineering Excellence Awards Competition.

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