Steel Bridge

From Free net encyclopedia

{{Infobox_Bridge |bridge_name=Steel Bridge |image=Steel-bridge-800x600.JPG |carries=upper: 4 traffic lanes and MAX
lower: Union Pacific Railroad (Amtrak) and walkway |crosses=Willamette River |locale=Portland, Oregon |maint=Union Pacific Railroad |design=Through truss with a double vertical lift span |mainspan=211 ft |width=71 feet |below=26 feet closed, 163 feet fully raised |open=1912 (replaced 1888 bridge) |lat=45.52778 |long=-122.66778}}

The Steel Bridge is a through truss, double lift bridge across the Willamette River in Portland, Oregon. It carries railroad and pedestrian traffic on the lower deck, and Highway 1W (former Route 99W), MAX light rail and a vintage streetcar on the upper deck, making it one of the most multimodal in the world. It is the only double-deck bridge with independent lifts in the world and the second oldest vertical lift bridge in North America.

It replaced the Steel Bridge that was built in 1888 as a double deck swing span bridge (photo). It was the first railroad bridge across the Willamette River in Portland. The name originated because steel, instead of wrought iron, was used in its construction.

The extant structure was built by Union Pacific Railroad and the Oregon Railway and Navigation Company at a cost of $1.7 million. It opened in July of 1912 to rail traffic and on August 9, 1912 to automobiles. Between 1984 and 1986 the bridge underwent a $10 million rehabilitation including MAX construction. In 2001, a 220 ft (67 m) long and 8 ft (2.4 m) wide cantilevered walkway was installed on the southern side of the bridge's lower deck as part of the Eastbank Esplanade (there are also narrow sidewalks on the upper deck). The bridge is currently owned by Union Pacific with the upper deck leased to Oregon Department of Transportation, and subleased to TriMet.

The lift span of the bridge is 211 ft (64 m) long. At low river levels the lower deck is 26 ft (7.9 m) above the water and 163 ft (49.7 m) of vertical clearance is provided when both are raised. Because of the independent lifts, the lower deck can be raised to 72 ft (22 m), telescoping into the upper deck but not disturbing it. Each deck has it own counterweights, 2 for the upper and 8 for the lower, that have a total moving weight of 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 bus lines), 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.<ref>Template:Cite web</ref>

The lower deck of the bridge was threatened by major floods in 1948, 1964, and 1996.

At the east end of the bridge is the Rose Garden and Oregon Convention Center and at the west end is the Portland Classical Chinese Garden and Chinatown district.

[edit]