Transcript Galloping Gertie’ The Tacoma Narrows Bridge Failure

‘Galloping Gertie’
The Tacoma Narrows Bridge
Failure
November 21, 2006
Max Walker
Robby Poshusta
Jan Kubicka
Aaron Aslin
History
► Started
November 23, 1938
► Opened to the Public July 1, 1940
► Designed by Clark Eldridge
► Altered by Leon Moisseiff
► Pacific Bridge Company, General
Construction Company, Columbia
Construction Company
Location
Random Facts
► Greatest
Span 2,800ft
► Total Length 5,979ft
► Cost – $8 million
► 17.25” Diameter Cables
► 6,308 wires spun one at a time to make the
large cables.
► Third largest suspension span in the world
at the time.
Engineering
Design Included:
► Suspension bridge
► Two Towers
► Two Main Cables
► Two Anchorages
► One Lane Highway
Engineering
Anchorages
Engineering
► False
Bottom Caisson
► 600 ton blocks of
concrete were used to
anchor the caisson
Collapse
Collapse
► 11am
on November 7,
1940
► 42 M.P.H. wind
► No one died in the
collapse
► Several cars were
thrown into the water
Collapse
Mechanical Resonance
► When the natural frequency of vibration
matches the frequency of oscillation
► A swing set
► The 42 mile and hour winds caused the
resonance
► Soldiers marching in lockstep over a bridge
can destroy it by creating resonance
Collapse
► The
force of the wind
when contacting the
thick garter on the
bridge matched the
natural frequency or
‘critical speed’ of the
bridge creating bigger
and bigger horizontal
oscillations
Collapse
Outcome
Incorporated the force from wind into the
design of bridges
► Used a vented garter and roadway
► Reinforced existing bridges
► Made bridges thicker and wider
►
Outcome
►
“The consulting
designer, Leon
Moisseiff felt the fall
occurred because
engineers did not
know enough about
aerodynamics, and
that lack of funds had
forced the building of a
bridge unprecedently
narrow for its length.
(University of
Washington- Special
Collections)”
Bibliography
►
University of Washington Special
Collections- Tacoma Narrows Bridge.
November 16, 2006.
<http://www.lib.washington.edu/specialcoll/
exhibits/tnb/default.html>
► WSDOT-
Tacoma Narrows Bridge: Extreme
History. November 16, 2006.
<http://www.wsdot.wa.gov/TNBhistory/>
Videography
Tacoma Narrows Bridge Collapse