Canal Street Railroad Bridge

View an article from Engineering Record discussing the construction of this bridge
View an article from the Journal of the Western Society of Engineers discussing the construction of this bridge (digitalized by Google)
View an article from Railway Age Gazette discussing the construction of this bridge
View an article from Railway Age discussing the construction of this bridge (digitalized by Google)

Located immediately east of Canal Street, this massive through truss vertical lift bridge is among the largest movable bridges across the Chicago River. The first bridge at this location was constructed in 1857, and consisted of a wooden swing bridge. In 1883, the bridge would be replaced by a double track 224-foot, 16-panel, pin-connected center balanced Pratt through truss swing bridge, set onto stone and wood substructures. This light iron truss utilized numerous features typical of spans from this era, including lightly laced members and a lattice style portal. The bridge was strengthened in 1893, and by the early 20th Century, the bridge had become obsolete for traffic. During the late 19th Century, the Chicago & Alton Railway and the Illinois Central Railroad obtained trackage rights over the PFW&C to connect to Union Station in Chicago. During the early 20th Century, improvements to the Chicago River also necessitated a larger clear channel. Waddell & Harrington was chosen to design a new bridge. A vertical lift design was chosen, which would give a much wider channel and vertical clearance under the bridge. The design and erection of the structure was overseen by J.C. Bland, Engineer of Bridges for Pennsylvania Railroad Lines west of Pittsburgh.

Construction on the bridge began in early 1913, starting with the construction of new concrete abutments and piers. The piers would consist of large rectangular concrete structures, and the abutments would use a design which would be perpendicular at each track. The northern piers were constructed wide enough for a second bridge, but the southern piers were not. The concrete piers were constructed on iron shells, which were sunk to bedrock approximately 55 to 60 feet deep. The abutments would be constructed on wooden piles, typical of bridges from this era. By late summer 1913, the substructures were completed.

In order to avoid interfering with traffic over the old bridge and on the waterway while the new bridge was constructed, the bridge would have to be erected on falsework in the raised position. In addition, the old bridge interfered with the south end of the new structure. To accommodate this, the south abutment was lengthened and the alignment of the tracks changed slightly to avoid interference. Erection on the south tower began in September 1913, and the towers were erected in three sections; the bottom section 81 feet tall, the middle section 47 feet tall and the top section 57 feet tall. Once the bottom sections of the towers were installed, these sections were fixed in place, and an "A" frame derrick was used for constructing the towers.

The main span of the bridge was constructed from the outside to the inside, and was supported by a fan-like falsework, which was fastened to the towers. A 108-foot gap underneath the main span remained free from obstruction to maintain railroad and river traffic. The main truss and the counterweights of the bridge were constructed simultaneously, and by July 1914, the bridge was nearly ready for traffic. The north end of the swing span was then placed on scows, and removed. The remaining portion of the swing bridge was then shifted and cut up. The new bridge was placed into service on July 30, 1914; and maintenance was turned over to the railroad. The new bridge took over a year to complete, and cost approximately $750,000. The fabrication and erection of the superstructure was completed by the Pennsylvania Steel Company, while the construction of the concrete substructures was completed by the Great Lakes Dredge & Dock Company. At the time of completion, this was the heaviest vertical lift bridge constructed, and the second largest ever built.

The main span of the bridge consists of a double track 280-foot, 10-panel riveted Parker through truss span, which utilizes heavily constructed members and a ballast deck. The portal bracings of the span consist of solid plates, and the sway bracing utilizes a lattice design. In addition, the bridge runs at a 47-degree skew, further complicating the design. The two towers of the bridge stand 195 feet above the concrete piers, and utilize heavily built up members. Underneath the towers, the tracks are set onto typical deck plate girder spans. The counterweights of the bridge are constructed of concrete and steel, and each weigh approximately 790 tons. These counteweights are connected to the bridge by 64 steel cables, which are set onto four rollers and 32 pulleys used to operate the bridge. During the design of the bridge, it was decided to make the bridge approximately 25 feet higher to allow for a future track elevation project. At one time, it was planned to add an additional set of tracks to the east side of the bridge, although these additional tracks were apparently never added. The machinery house is located in the middle of the span. At full height, the bridge raised provides a 120-foot clearance beneath the structure.

John Alexander Low Waddell had become prominent as a bridge engineer during the 1890s, specializing in railroad bridges. While lift bridges had been in use on some scale for centuries, Waddell developed the first mechanized vertical lift bridge at Duluth, Minnesota in 1892; although this was objected by the War Department. The first vertical lift span constructed was the South Halsted Street Bridge in Chicago, constructed in 1893. Waddell quickly obtained patents for the vertical lift design, preventing the design from being further constructed or improved upon. The second vertical lift bridge would not be constructed until Waddell partnered with John Harrington to form Waddell & Harrington in 1907. Waddell was often on the forefront of revolutionary bridge design, often convincing railroads to try unique and experimental spans. While a unique and convenient design, only one other bridge of this design would be constructed in Oregon. Waddell & Harrington continued to develop and patent the vertical lift design, designing numerous roadway and railroad lift bridges throughout the United States.

While Chicago is known for movable bridges, this span is believed to be the only vertical lift railroad bridge over the Chicago River. Many of the movable bridges in Chicago used swing or bascule designs, which were well suited for bridges constrained by space. The unusual angle of the river, and requirements to maintain both railroad and river traffic likely led to the construction of a vertical lift bridge instead of a bascule design at this location. Today, the bridge continues to serve Amtrak, as well as the Metra Southwest Service and Heritage Coordinator. Overall, the bridge appears to be in fair condition, but has become an operational problem. The bridge is known for delaying traffic, as it often gets stuck. Proposals have been made to replace the bridge with a higher fixed structure, but no funding or engineering plans have been completed for this work. The author has ranked the bridge as being highly significant, due to the size, age and design of the structure.