Friday, September 11, 2009

Portland's Bridges: Broadway Bridge

About half a mile upstream from the Fremont Bridge (across the Willamette River) is the Broadway Bridge. It is an unusual Rall-type bascule bridge, which was chosen as the low bidder in a competition. However, the complex mechanism (it rolls back on rails as it lifts) has required frequent repairs and has been more expensive in the long run.

The bridge was designed by Ralph Modjeski and built by the Pennsylvania Steel Company over two years at a cost of $1.6 million. It had the world's longest double leaf bascule span when it was completed in 1913.

The main piers are reinforced concrete faced and topped with granite. The approach piers are 12 ft diameter concrete-filled steel pipes tied together with cross-bracing. A 278 ft double-leaf bascule span is supported on the main piers and crosses over the shipping channel. It provides 70 ft vertical clearance when closed and is opened about once a day. An operator's house is above each of the main piers (on the other side of the bridge). The approach spans are steel, camelback trusses. A reinforced concrete ramp on the west side goes over Union Station and carries traffic on and off the bridge. A similar ramp on the east side goes over Highway 99 and light rail tracks.

The bridge is 1742 ft long and 70 ft wide. It has two lanes of traffic in each direction and two broad sidewalks. It carries about 2700 vehicles and 1200 bicycles a day. It has been frequently repaired and renovated over the years. The concrete deck was replaced with a steel grating in 1948 to make it easier to lift. The steel deck was replaced with a fiber-reiforced composite material in 2005.

I'll just mention that Portland, Oregon is a very nice, attractive city with a very efficient transportation system. The area around the Willamette River is particularly pleasant and attracts large crowds on the weekends.
Creative Commons License
Portland's Bridges: Broadway Bridge by Mark Yashinsky is licensed under a Creative Commons Attribution-NonCommercial-ShareAlike 3.0 United States License.

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