Bridge in the sky

March 3rd, 2010 by Gene

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Bridges are some of the coolest things engineers build. We’ll check out a nifty one. Today, on Engineering Works!

The Hoover Dam on the Colorado River is one of the biggest and most complex engineering projects ever. The water and electric power it provides made Las Vegas and other Western sun belt cities possible. But it doesn’t make a very good bridge. US 93 crosses the Black Canyon of the Colorado on top of the dam. The highway there is only two lanes wide and twists and turns a lot on either side of the dam. The highway is a major NAFTA route through Arizona, Colorado and Utah, and more than 14-thousand vehicles cross it every day. Sometimes traffic gets pretty tied up around the dam.

Engineers started building a real bridge about a quarter-mile south of the dam in 2005. It’s an impressive project. The roadway crosses the canyon 900 feet above the river on an arch and columns that seem to hang in the air. The bridge itself is almost 2,000 feet long and carries four lanes of traffic and a sidewalk so tourists can get a good view of the dam.

Building it was a bit of a trick. They started the arch from both sides of the canyon, and it met in the middle. A network of cranes and cables kept it up until the two halves met.

We’ve crossed our bridge today and we’ll be on our way. See you next time.

Engineering Works! is made possible by Texas A&M Engineering and produced by KAMU-FM in College Station. Learn more about engineering. Visit us on the World Wide Web.

http://engineeringworks.tamu.edu

For more:

http://www.hooverdambypass.org/

http://scienceray.com/technology/engineering/the-incredible-hoover-dam-bypass-bridge-under-construction/

http://en.wikipedia.org/wiki/Mike_O%27Callaghan_%E2%80%93_Pat_Tillman_Memorial_Bridge