Tacoma Narrows Bridge

Infobox_Bridge
bridge_name = Tacoma Narrows Bridge

---

caption = Facing west atop the Tacoma Narrows
carries = State Route 16
crosses = Tacoma Narrows
design = Dual Suspension
locale = Tacoma to Gig Harbor, Washington flagicon|US
open = October 14 1950 (westbound)
July 15 2007 (eastbound)
toll = Eastbound only: $4.00 (cash/credit price),
$2.75 (transponder price)
mainspan = 2,800 ft (853 m)
length = 5,979 ft (1822 m)
below = 187.5 ft (57.15 m)The Tacoma Narrows Bridge is a pair of mile-long suspension bridges in the U.S. state of Washington, which carry State Route 16 across the Tacoma Narrows between Tacoma and the Kitsap Peninsula. They replaced a bridge that was opened to traffic on July 1 1940 and later became famous four months later for a dramatic wind-induced structural collapse that was caught on motion picture film. The original span's motion earned it the nickname "Galloping Gertie".

Due to materials shortages as a result of World War II, it took 10 years to build a replacement bridge, which opened October 14 1950. The 1950 replacement bridge was sometimes referred to as "Sturdy Gertie", and, like its predecessor, was the third longest suspension span in the world at the time of its construction. Population growth on the Kitsap peninsula caused the bridge to exceed its vehicle capacity, and a parallel bridge was constructed to carry eastbound traffic, while the 1950 bridge was reconfigured to carry westbound traffic. The new bridge opened July 15, 2007, making the Tacoma Narrows Bridge the longest twin suspension span in the world.

Galloping Gertie

The desire for the construction of this bridge dates back to 1889 with a Northern Pacific Railway proposal for a trestle, but concerted efforts began in the mid-1920s. In 1937, when the Washington State legislature created the Washington State Toll Bridge Authority and appropriated $5,000 to study the request by Tacoma and Pierce County for a bridge over the Narrows.

The first Tacoma Narrows Bridge opened to traffic on July 1 1940. It collapsed four months later on November 7 1940, at 11:00 AM (Pacific time) due to a physical phenomenon known as aeroelastic flutter caused by a convert|67|km/h wind. The bridge collapse had lasting effects on science and engineering. In many undergraduate physics texts the event is presented as an example of elementary forced resonance with the wind providing an external periodic frequency that matched the natural structural frequency (even though its real cause of failure was aeroelastic flutter). Its failure also boosted research in the field of bridge aerodynamics/aeroelastics which have themselves influenced the designs of all the world's great long-span bridges built since 1940.

No human life was lost in the collapse of the bridge. The collapse of the bridge was recorded on film by Barney Elliott, owner of a local camera shop, and shows Leonard Coatsworth leaving the bridge after exiting his car. In 1998, "The Tacoma Narrows Bridge Collapse" was selected for preservation in the United States National Film Registry by the Library of Congress as being "culturally, historically, or aesthetically significant." This footage is still shown to engineering, architecture, and physics students as a cautionary tale.

After the collapse, two bridges were constructed in the same general location. The first one, now called the Tacoma Westbound bridge, is 5,979 feet (1822 m) long — 40 feet (12 m) longer than Galloping Gertie. The second one, the Tacoma Eastbound Bridge, opened in 2007.

Westbound bridge

The current westbound bridge was designed and rebuilt with open trusses, stiffening struts and openings in the roadway to let wind through. It opened on October 14 1950, and is 5,979 feet (1822 m) long — 40 feet (12 m) longer than the first bridge, Galloping Gertie. Local residents nicknamed the new bridge Sturdy Gertie, as the oscillations that plagued the previous design had been eliminated. This bridge along with its new parallel eastbound bridge are currently the fifth-longest suspension bridges in the United States.

When built, the westbound bridge was the third-longest suspension bridge span in the world. [cite book | last= Holstine | first = Craig E. | title = Spanning Washington : historic highway bridges of the Evergreen State | publisher = Washington State University Press | pages = 61-62 | year = 2005 | isbn = 0-87422-281-8 ] Like other modern suspension bridges, the westbound bridge was built with steel plates that feature sharp entry edges rather than the flat plate sides used in the original Tacoma Narrows Bridge (see the suspension bridge article for an example).

The bridge was designed to handle 60,000 vehicles a day. It carried both westbound and eastbound traffic until the eastbound bridge opened on July 15, 2007. [Beekman, Dan and Santos, Melissa; [http://www.thenewstribune.com/news/updates/story/110831.html "First traffic crosses new bridge"] ; "The News Tribune"; July 16, 2007]

Eastbound bridge

In 1998, voters in several Washington counties approved an advisory measure to create a second Narrows span. Construction of the new span, which carries eastbound traffic parallel to the current bridge, began on October 4 2002, and was completed in July 2007. The Washington State Department of Transportation collects a toll before entering the eastbound span, at $2.75 for Good to Go! account holders with in-vehicle transponders and a $4.00 toll for cash/credit card paying customers. The existing span has been toll-free since 1965. The new bridge marks the first installation of the new Good To Go! electronic toll collection system.

A group called [http://www.narrowsbridgelights.org/ NarrowsBridgeLights.org] advocates illuminating both bridges with twinkling lights. The group recommends solar powered lighting, for both safety and beauty. [Carson, Rob; [http://www.thenewstribune.com/front/topstories/story/110840.html "It's open: Sneakers, paws, stroller wheels create first traffic jam"] ; "The News Tribune"; July 16, 2007]

Gallery

References

External links

* [http://www.citynoise.org/article/5410 Photos of the bridge and the new span under construction]
*Structurae|id=s0000074|title=Tacoma Narrows Bridge (1940)
*Structurae|id=s0000484|title=Tacoma Narrows Bridge (1950)
*Structurae|id=s0001290|title=New Tacoma Narrows Bridge (2007)

Historical

* [http://www.wsdot.wa.gov/TNBhistory/spanning_time.htm Timeline of the bridges]
* [http://www.nwrain.net/~newtsuit/recoveries/narrows/narrows.htm Tacoma Narrows Bridge]

econd span project

* [http://www.wsdot.wa.gov/projects/sr16narrowsbridge/ Tacoma Narrows Bridge Project] (WS DOT Web Page; information about the new bridge construction project)
* [http://www.wsdot.wa.gov/projects/sr16narrowsbridge/enlarged_designviz.cfm SR 16 - New Tacoma Narrows Bridge] (computer projection of completed project)
* [http://www.sireneinternet.net/pstran/tnb Puget Sound Transportation projects:Tacoma Narrows Bridge] (unofficial site providing news, photos and information about the second span construction)
* [http://www.nrc-cnrc.gc.ca/highlights/2003/0306tacoma_e.html Wind Tunnel Testing Summary] from the National Research Council of Canada
* [http://www.nrc-cnrc.gc.ca/newsroom/news/2003/tacoma03_e.html Wind Tunnel Testing Press Release ] from the National Research Council of Canada
* [http://www.thenewstribune.com/news/projects/narrows_bridge/ Tacoma Narrows Bridge Project] (continuing coverage of bridge construction from "The News Tribune")
* [http://www.kitsapsun.com/bsun/local/article/0,2403,BSUN_19088_4108100,00.html Bridge Workers are Walking Tall Above the Narrows] Rob Carson (The News Tribune), "Kitsap Sun", September 25 2005
* [http://seattletimes.nwsource.com/html/localnews/2002562232_narrows15m.html Wire by wire, Tacoma Narrows bridge is built] Mike Lindblom, "The Seattle Times", October 15 2005