This bridge is one of the most unique movable bridges in the country. The vertical lift bridge was designed by famous engineers and vertical lift proponents John Alexander Low Waddell and John Lyle Harrington. The bridge is a double-deck structure with vehicular traffic on the upper level and railroad traffic on the lower level. The bridge is specially designed so that the lower deck can be raised without raising the upper deck. The lower deck is hung from the upper deck by hangers, and cables inside the vertical lift truss are able to pull the hangers up inside the vertical members, raising the lower deck up to just below the upper deck. This position would allow for medium sized boats to get under the bridge without interrupting vehicular traffic. For larger boats, the entire bridge can then be lifted in a more traditional fashion, providing the full height clearance afforded by the towers of the bridge.
The configuration of the upper deck of this bridge is unusual because it includes a vehicular traffic lane that is cantilevered out on each side of the truss, in addition to the roadway provided in the traditional space between the truss lines.
In addition to its unique design, this bridge is an early surviving lift bridge designed by Waddell and Harrington, which was the company which pioneered and popularized the modern vertical lift bridge starting with a lift bridge built in Chicago on Halsted Street in 1893.
This bridge's lower deck is raised in a similar manner to the ASB Bridge in Kansas City, also designed by Waddell and Harrington. The ASB Bridge lacks the ability to raise its upper deck however. For this reason, the Steel Bridge is the only one of its kind in the United States, where each deck can be raised independently.
Although the name "Steel Bridge" is an accurate description of this bridge, the name originated from the previous bridge at this location which was the first of its kind in the city.
Thanks to the addition of a sidewalk on the lower deck of this bridge in more recent years, it is possible for visitors to walk both the upper and lower deck of this bridge.
The bridge includes an extensive ramp approach system at the western end as well as several approach spans at the eastern end. Because of this as well as the double-deck design, measuring the total bridge length depends on which deck and ramp you are measuring. Another oddity is that the main span is not the largest span. The approach truss spans are listed with a 287 foot span, while the main lift span is 211 feet. The total length given in the technical facts table refers to the lower deck. Measuring the longest ramps on the bridge, the total length of the upper deck approaches 1800 feet.
Oregon's Historic Bridge Inventory indicates a number of companies who built the bridge. A historical article mentions that the American Bridge Company built the bridge. It is assumed American Bridge Company fabricated (and possibly erected) the superstructure, while United Engineering and Construction Company of Portland, Oregon may have acted as a general contractor for the superstructure. Oregon Railroad and Navigation Company, listed as a builder of the bridge by the inventory, might be better described as an owner or financer.
Information and Findings From Oregon's Historic Bridge Inventory
Three double-deck riveted Pratt trusses with the center truss being a 211-ft long two stage lift span.
Waddell and Harrington, Kansas City
Oregon-Washington Railway and Navigation Co. (Builder); United Engineering and Construction Co., Portland (Superstructure); Robert Wakefield and Co., Portland (Substructure)
The first bridge built at this location in 1888 used steel as its main building material, the first such occurrence in Portland, thus the name the Steel Bridge, which remains on the modern bridge. The current Steel Bridge replaced that first one in 1912, and maintained the tradition of innovation in bridge design set by its predecessor. At the time of its opening, the 1912 Steel Bridge claimed to be the largest telescoping bridge in the world. The telescoping, two-stage lift action of the bridge still functions, allowing the lower rail-carrying deck to lift without disturbing traffic on the upper deck. For larger vessels, both decks can be raised, giving a maximum clearance of 163-ft.
Character Defining Features
Structure type, Location, Decorative railing, Multimodal functionality, Mechanism
Major alterations include the addition of a light rail line to the upper deck of the bridge and the addition of a pedestrian bridge on the lower deck.
Bridge Considered Historic By Survey: Yes
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