Steel Bridge

97227 Portland, OR, Estados Unidos (Oregon )

From Wikipedia, the free encyclopedia:
The Steel Bridge is a through truss, double-deck vertical-lift bridge across the Willamette River in Portland, Oregon, United States, opened in 1912. Its lower deck carries railroad and bicycle/pedestrian traffic, while the upper deck carries road traffic (on the Pacific Highway West No. 1W, former Oregon Route 99W) and light rail (MAX), making the bridge 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, after the nearby Hawthorne Bridge. The bridge links the Rose Quarter and Lloyd District in the east to Old Town Chinatown neighborhood in the west.

Steel Bridge

Carries: Upper: 2 outer lanes for general traffic, 2 inner lanes solely for MAX Light Rail, and sidewalks on both sides
Lower: Union Pacific Railroad (incl. Amtrak toward Eugene) and walkway

Crosses: Willamette River

Owner: Union Pacific Railroad

Design: Through truss with a double vertical-lift span

Width: 71 feet (22 m)

Longest span: 211 feet (64 m)

Clearance: below26 feet (7.9 m) closed, 72 feet (22 m) lower deck raised, 163 feet (50 m) fully raised

Opened: 1912 (replaced 1888 bridge)

History

The bridge was completed in 1912 and replaced the Steel Bridge that was built in 1888 as a double-deck swing-span bridge. The 1888 structure was the first railroad bridge across the Willamette River in Portland. Its name originated because steel, instead of wrought iron, was used in its construction, very unusual for the time. When the current Steel Bridge opened, it was simply given its predecessor's name.

Structure and lift operation

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 its own counterweights, two for the upper and eight for the lower, totaling 9,000,000 lb (4,100 metric tons).

The machinery house sits atop the upper-deck lift truss. The operator's room is suspended from the top of the lift-span truss, directly below the machinery house, so that the operator can view river traffic as well as the upper deck. After the 2001 addition of a pedestrian walkway on the lower deck, cameras and closed-circuit television monitors were added to allow the operator to view the lower-deck walkway.

Until the bridge's mid-1980s renovation, the crossing gates blocking the roadway and sidewalks during raising of the upper-deck lift span were manually operated, rotated horizontally across the roadway by two "gate tenders", one on each side of the lift span. Small shacks for the gatekeepers were positioned on the roadway deck, between the inner and outer traffic lanes, but they were removed during the 1980s rebuilding and replaced by a new gate tender house positioned above the roadway, in the west lift tower. Powered crossing gates replaced the manual ones, and operation of the gates is now automated, controlled by the bridge operator

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