Structure
The lift span of the bridge is 211 feet (64 m) long. At low river levels the lower deck is 26 feet (7.9 m) above the water, and 163 feet (50 m) of vertical clearance is provided when both decks are raised. Because of the independent lifts, the lower deck can be raised to 72 feet (22 m), telescoping into the upper deck but not disturbing it. Each deck has it own counterweights, two for the upper and eight for the lower, totaling 9,000,000 lb (4,100 metric tons).
The machinery house is above the upper-deck lift span with an operator's room suspended below the house so that the operator can view river traffic as well as the upper deck. The average daily traffic in 2000 was 23,100 vehicles (including many TriMet buses), 200 MAX trains, 40 freight and Amtrak trains, and 500 bicycles. The construction of the lower-deck walkway connected to the Eastbank Esplanade resulted in a sharp increase in bicycle traffic, with over 2,100 daily bicycle crossings in 2005.
Read more about this topic: Steel Bridge
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