‘‘Galloping Gertie’Galloping Gertie’The Tacoma Narrows The Tacoma Narrows

Bridge FailureBridge Failure

November 21, 2006November 21, 2006

Max WalkerMax Walker Robby PoshustaRobby Poshusta

Jan KubickaJan Kubicka Aaron AslinAaron Aslin

HistoryHistory

►Started November 23, 1938Started November 23, 1938►Opened to the Public July 1, 1940Opened to the Public July 1, 1940►Designed by Clark EldridgeDesigned by Clark Eldridge►Altered by Leon MoisseiffAltered by Leon Moisseiff►Pacific Bridge Company, General Pacific Bridge Company, General

Construction Company, Columbia Construction Company, Columbia Construction CompanyConstruction Company

LocationLocation

Random FactsRandom Facts

►Greatest Span 2,800ftGreatest Span 2,800ft►Total Length 5,979ftTotal Length 5,979ft►Cost – $8 millionCost – $8 million►17.25” Diameter Cables17.25” Diameter Cables►6,308 wires spun one at a time to 6,308 wires spun one at a time to

make the large cables.make the large cables.►Third largest suspension span in the Third largest suspension span in the

world at the time.world at the time.

EngineeringEngineering

Design Included:Design Included:► Suspension bridgeSuspension bridge► Two TowersTwo Towers► Two Main CablesTwo Main Cables► Two AnchoragesTwo Anchorages► One Lane HighwayOne Lane Highway

Anchorages

EngineeringEngineering

EngineeringEngineering

► False Bottom CaissonFalse Bottom Caisson► 600 ton blocks of 600 ton blocks of

concrete were used concrete were used to anchor the caissonto anchor the caisson

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► 11am on November 11am on November 7, 19407, 1940

► 42 M.P.H. wind42 M.P.H. wind► No one died in the No one died in the

collapsecollapse► Several cars were Several cars were

thrown into the thrown into the waterwater

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Mechanical ResonanceMechanical Resonance►When the natural frequency of vibration When the natural frequency of vibration

matches the frequency of oscillation matches the frequency of oscillation ►A swing setA swing set►The 42 mile and hour winds caused the The 42 mile and hour winds caused the

resonanceresonance►Soldiers marching in lockstep over a Soldiers marching in lockstep over a

bridge can destroy it by creating bridge can destroy it by creating resonanceresonance

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► The force of the wind The force of the wind when contacting the when contacting the thick garter on the thick garter on the bridge matched the bridge matched the natural frequency or natural frequency or ‘critical speed’ of the ‘critical speed’ of the bridge creating bridge creating bigger and bigger bigger and bigger horizontal horizontal oscillationsoscillations

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OutcomeOutcome

► Incorporated the force from wind into Incorporated the force from wind into the design of bridgesthe design of bridges

►Used a vented garter and roadwayUsed a vented garter and roadway►Reinforced existing bridgesReinforced existing bridges►Made bridges thicker and widerMade bridges thicker and wider

OutcomeOutcome

► ““The consulting The consulting designer, Leon designer, Leon Moisseiff felt the fall Moisseiff felt the fall occurred because occurred because engineers did not engineers did not know enough about know enough about aerodynamics, and aerodynamics, and that lack of funds that lack of funds had forced the had forced the building of a bridge building of a bridge unprecedently unprecedently narrow for its length. narrow for its length. (University of (University of Washington- Special Washington- Special Collections)”Collections)”

BibliographyBibliography

► University of Washington Special University of Washington Special Collections- Tacoma Narrows Bridge. Collections- Tacoma Narrows Bridge. November 16, 2006. <November 16, 2006. <http://www.lib.washington.edu/specialchttp://www.lib.washington.edu/specialcoll/exhibits/tnb/default.htmloll/exhibits/tnb/default.html>>

►WSDOT- Tacoma Narrows Bridge: WSDOT- Tacoma Narrows Bridge: Extreme History. November 16, 2006. Extreme History. November 16, 2006. <<http://www.wsdot.wa.gov/TNBhistory/http://www.wsdot.wa.gov/TNBhistory/> >

VideographyVideography

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