BNSF North Avenue Bridge (Aurora)

View an article discussing this track elevation project (digitized by Google)
View an article discussing this track elevation project (digitized by Google)
View an article discussing this track elevation project (digitized by Internet Archive)

Located in Aurora, this concrete slab bridge carries the former Chicago, Burlington & Quincy Railroad over North Avenue. Since the CB&Q reached Aurora in the 1849, the city had served as a major terminal for the CB&Q. In the early 20th Century, railroad congestion became a serious concern for residents in Aurora. The City of Chicago had successfully ordered elevations of various railroads throughout the city, resulting in the construction of retaining walls, with underpasses constructed at the street crossings. Understanding the concerns of the public, the CB&Q sought to improve operations and fix the traffic problem by realigning and elevating the tracks through Aurora. Construction on the project began in 1914, although much of the work was delayed due to World War I. Work on the project resumed in 1919, with the bridge opening to eastbound traffic in April 1920 and westbound traffic in September of that year. The entire project was completed in November 1922, at a cost of $4,500,000. The railroad spared no expense, constructing new facilities and including decorative features in the bridges. The use of retaining walls on the project was minimized, as discoloration and cracking proved to be visually unappealing on earlier track elevation projects in Chicago. Design and construction of the project was under A.W. Newton, Chief Engineer of the railroad. Company forces constructed all of the concrete work, and contractors were used for the earthwork.

The bridge at North Avenue consists of a concrete slab structure, constructed for six tracks. The bridge consists of two 25-foot concrete slab spans, approached by a 10-foot span on either end. The entire bridge would be set onto concrete substructures. Due to the angle of which the railroad crosses North Avenue, the bridge is constructed at a heavy skew. The bridge is constructed in a trapezoidal shape, with the east end wider than the west end. During construction, the slabs of the bridge were cast in place in panels of approximately 8 feet wide. To help set the edge of the skewed spans, a steel through girder was used, which was encased in concrete at the end of construction. By using a fasica girder, this allowed the ends of the slabs to be square, and simplified the structure. The abutments, approach spans and outer piers of the bridge were constructed monlithically on a large spread footing. In addition, the center pier also rests on a spread footing. This design was used to minimize the amount of concrete needed to construct the foundation. Columns of the piers use a square design, and other decorative imprints were used throughout the bridge. Concrete bridges such as this were the most popular design for track elevations in the 1910s and 1920s, as the design was durable, easy to construct and was cost effective. In addition, decorative features could easily be added to the structure to improve the overall aesthetics. Only two tracks remain in use on the bridge today.Overall, the bridge appears to be in fair condition, with some spalling noted throughout the structure. The author has ranked this bridge as being locally significant, due to the common design.