The bridges spanning the north branch of this urban river have become increasingly obsolete as the economy, transportation patterns, and the demographic make up of this city have changed over the last 40 years. As industrial river traffic flowing below the bridges has decreased, automobile traffic running over them has jumped dramatically. The aging lift bridges no longer operate in most cases and are in need of substantial maintenance and repairs. With this in mind local transportation agencies have embarked on a systematic evaluation and replacement strategy which aims to provide efficient river crossings which add value to the city’s urban fabric.
The North Avenue Bridge is the second installment of a major new iconic bridge crossing this river. It replaced a 2 lane 2 leaf bascule bridge which was about 100 years old. The old red bridge was a neighborhood icon in its own right but could no longer serve the intensive transportation needs of the community. To replace a cherished piece of the city landscape, the city determined that the design for the replacement had to be carefully considered.
The iconic new bridge has instantly become a new landmark on the Chicago River. Its structure, comprised of a composite cable stay/ suspension system, is the only one of its type in the city. The center of the main span is held by the suspension cables, while the remainder of the roadway is supported by cables which radiate from the towers. The busy crossing provides two sidewalks and four lanes of traffic between two rapidly growing neighborhoods and creates a link from west to east with improved traffic flow. Nearly 40,000 cars a day cross the bridge. Beyond the mundane statistics the bridge also greatly enhances the urban fabric. It opens up spectacular skyline views and forms an impressive backdrop to a previously hidden river turning basin, a little known lake in the center of the city. Special attention was paid to details which not only make for easy passage by car but also provide a pleasant street level experience for pedestrians. This bridge integrates itself into the fabric of the city, becoming more than a simple conveyance.
The light weight structural appearance and soaring support towers give suggestions of a city which is advanced and forward thinking. Elegant guard rails of woven stainless steel provide a high level of detail and finesse at the pedestrian level.
The design of this bridge is the result of a strong collaboration between the architects and engineers. For many decades architects have been relegated to minor roles in bridge design if any at all. This has resulted in transportation systems which degrade the urban fabric. Including architects in the design of what has historically been a civil engineering exercise has resulted in a North Avenue Bridge that is far more than a transportation device. This bridge has succeeded in enhancing its environment.