|Photo from HAER ORE,26-PORT,14--14 (CT) from or0291|
GENERAL VIEW FROM BROADWAY BRIDGE TO THE NORTH
The 1912 Steel Bridge is significant for its vertical lift design. This is a double-decked bridge; the lower deck is a railroad deck while the upper deck is used for highway and light rail traffic. The two decks may be lifted at the same time, or the lower deck may be raised independently of the upper deck, telescoping into the latter. The Steel Bridge was the first bridge built with this independent lifting system and is the only one of this type existing in the United States today. This type of bridge was designed by J.A.L. Waddell, who engineered the South Halstead Street Bridge inChicago, Illinois, the first significant vertical lift bridge in the United States. [HAER-data]The bridge is normally 26' above low water. When the lower deck is raised, there is 72' of clearance. Raising both decks provides 139' of clearance. [HAER-data]
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. [Historic Bridges]The ABS Bridge also can raise the lower deck up into the upper deck, but the upper deck is fixed. This is the only bridge in the United States that can raise both decks.
|Photo from HAER ORE,26-PORT,14--24 (CT) from or0291|
|Photo from HAER ORE,26-PORT,14--22 (CT) from or0291|
|Railway Review, p137|
[This is a reminder that the reason lift bridges needed such tall towers at the interesting turn of the century is that sailing ships were still common. And we can see that tugboats that are travelling "light" needs just the lower deck raised even though they are steam powered and have a tall smokestack.]
|Beill Neill shared a NOLA Rails post|
SP trein #2 the Cascade at Portland OR, 1964.
Norm Anderson You can see the tower of Portland Union Station through the girders of the bridge. Some of the passengers are already gathering their belongings, preparing to detrain.
|Drawing from HAER ORE,26-PORT,14- (sheet 1 of 3) from or0291|
|Drawing from HAER ORE,26-PORT,14- (sheet 2 of 3) from or0291|
|Drawing from HAER ORE,26-PORT,14- (sheet 3 of 3) from or0291|
|Railway Review, p138|
[The sheaves for this bridge are 14' in diameter. Developing bearings that could hold the weight of the counterweights and half the spans was one of the major engineering issues Waddell had to solve when designing the lift bridge, for which he obtained the patents.]
|[Bridge Engineering by J. A. L. Waddell, Digitized by Google, p732]|
Historic Bridges had this reference of other Portland bridges included with this bridge. For now at least, I'm going to note it here.
|or0316, this document has several more Portland bridge diagrams|
While I'm using these notes as a placeholder for Portland bridges, here is another overview of the bridges on a T-shirt that my daughter bought me the year she was a coach at Oregon State University.