Reconstruction of North Avenue Bridge over the Chicago River, Chicago, Illinois

Abstract

This project involves the removal of an inoperable bascule bridge carrying North Avenue over the Chicago River and the construction of a wider, fixed-span structure at the same location in Chicago, Illinois. A hybrid structural system was selected for the new structure to meet various geometric and clearance constraints, provide for future utilization of the riverbanks adjacent to the structure, and provide for an aesthetic structure. The hybrid structural system consists of a combination of a self-anchored suspension bridge and a cable-stayed bridge. The bridge consists of a 252-ft main span and two 84-ft back spans. The middle portion of the main span is supported by suspension cables and hangers, and the remainder of the main span and both back spans are supported by cable stays arranged in a fan or semiharp configuration. Galvanized structural strands are used for the suspension cable and hangers, and prestressing steel strands are used for the cable stays. Steel pylons support the cable stays and suspension cable. The bridge deck will be posttensioned and constructed from high-performance concrete to provide greater durability and strength characteristics. This project is a pioneer effort in applying the innovative cable-stayed-suspension hybrid system. The design will serve as a good opportunity to study the behavior of such a unique structural system and provide valuable knowledge for its future applications.