Monday, October 14, 2013

The short-lived snag

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I know I promised this on Sunday, but I didn't feel very well all day--felt a chill, didn't even make it to my Northwest Film Center's Reel Music Festival documentary, THIS AIN’T NO MOUSE MUSIC!


I walked to the corner of SE Grand Avenue and East Burnside. When I stopped at the bus shelter, I immediately noticed that the Burnside Bridge was up. The snag. I'm on the east side of the Willamette, waiting for an eastbound bus which is coming from the other side of the Willamette River. I took this photo at 3:02 p.m. By 3:07, the bridge was closed and traffic appeared in the eastbound lanes. Naturally, I don't know the entire length of time that the bridge was open, just the span of time from when I saw it completely open until it was completely shut--I'd say five minutes is a short snag when something that huge is involved! Soon the bus came and I rode home. In another example a serendipitous positioning of structures in a photo, look at the line up here--the Big Pink, the Burnside Bridge's Italian Renaissance tower where sometimes there is an operator inside, and the open bridge structure. I'm a huge fan of serendipity!

I'll never forget the first time that I drove west on Burnside back when we lived in Northwest Portland. I was headed across the river, can't remember why now, but as I got closer to the bridge, my mind filled with confusion as I realized cars were stopped in front of me. Then I saw a big shape on the horizon and thought, "They're moving a house across the bridge. Nope! That's the bridge! It's up!" My first time ever to approach an open bridge in Portland. What a treat!

Here's information from the Multnomah County Web site about the Burnside Bridge:

One of four Willamette River crossings built in Portland during the "Roaring Twenties," the Burnside Bridge stands in age right behind the County's Hawthorne and Broadway bridges.

This 1926 structure is located on one of the longest and busiest streets in the Portland area. The five-lane Burnside is a direct connection between downtown Portland, Beaverton to the west and Gresham to the east. Last year, about 40,000 vehicles a day used it. So did more than 1,000 pedestrians and bicyclists each day.

In addition to its important daily work load, Burnside plays a key role during emergencies. Burnside Street and bridge are designated as an official emergency transportation route. The bridge, as part of this "lifeline corridor," is the one non-freeway river crossing which emergency vehicles and suppliers are asked to use.

Burnside's artistic side

The three-span Burnside is a historically significant structure. It is the only Willamette River bridge in Portland designed with the help of an architect, a result of the early 20th century City Beautiful Movement that called for adding architectural ornamentation to engineering designs. The bridge's distinctive Italian Renaissance towers reflect the trend. Burnside is eligible for the National Register of Historic Places and protected by preservation laws. Originally designed by the firm of Hedrick and Kremers, Burnside was completed by Gustav Lindenthal (1850-1935). Burnside's opening mechanism, or bascule, was designed by Joseph Strauss (1870-1938), whose Golden Gate suspension bridge would open 11 years after Burnside.

The Burnside Bridge main river structure consists of two 268-foot side span steel deck truss side spans and a 252-foot double-leaf Strauss trunnion bascule draw span. The bridge originally had six lanes of traffic, but in 1995 the City of Portland requested that bike lanes be added to the bridge, so one lane of traffic was converted into two bike lanes. There are sidewalks on both sides of the bridge. The overall width of the structure is 86 feet. Vertical clearance of the closed bascule span is adequate for the majority of river traffic, with openings necessary only about 40 times per month.

Only minor modifications have been made to the bridge since its construction. Electric street car rails were removed in the late 1940’s, lighting and traffic control devices were updated in the late 1950’s, automobile traffic gates were installed in 1971 and the bascule pier fenders were replaced in 1983. Several deck resurfacing projects and expansion joint repairs have also taken place.

The east approach to the bridge is approximately 849 feet long and has two distinct types of construction. The first eight spans consist of steel plate girder spans ranging from 75 feet to 106 feet in length. The steel girders and steel interior floor beams are completely encased in concrete. A concrete deck spans the floorbeams. The next seven spans are composed of concrete stringers spanning continuously over concrete columns and floorbeams. Six of these spans are 22 feet long and one is 40 feet long.

The west approach is approximately 604 feet long and consists of 19 reinforced concrete spans ranging in length from 22 feet to 62 feet. The first 13 spans average 22 feet and consist of reinforced concrete stringers acting continuously over concrete columns and floorbeams. The next three spans average 40 feet in length and are of similar construction. The last four spans are 62 feet long and consist of four main simple span concrete girders that carry interior concrete floor beams and stringers. A concrete deck is cast with the girders, stringers and floorbeams.

And a bit about a bascule bridge:

Bascule bridges have sections that rotate upward and away from the centerline of the river, providing clear passage for river traffic. Side-by-side on the Willamette River in downtown Portland, the Morrison and Burnside Bridges are two examples of bascule bridges. These two bascule type bridges have a very clean, uncluttered look to them because the counterweights and operating machinery are located out of sight in the piers supporting the bridge. The Morrison Bridge is a Chicago-type bascule bridge, and the Burnside Bridge is a Strauss-type bascule bridge.

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