THE TACOMA BRIDGE FAILURE
.The Tacoma Bridge was 1810m long suspension bridge located in
Washington State, near Puget
.It carry the state rout 16 across the Tacoma narrows between Tacoma and Gig Harbor.
.It stretched like a steel ribbon across Puget Sound.
. It was the 3rd longest suspension bridge at that time in the world .
ËœTHE GALLOPING GERTIEÂ¦â„¢
Even during the construction phase unusual things happened to the bridge: gentle breezes caused vertical oscillation of the roadbed. A variety of band-aids were installed to combat this prior to opening and the University of Washington committed to further study the problem.
In no time at all, the locals nicknamed the bridge, Galloping Gertie. Thousands drove hundreds of miles to experience crossing the undulating center span. For four months, the Toll Bridge Authority enjoyed a boom time as traffic was about three times what they had expected.
Concerns about the bridgeâ„¢s stability had been voiced, but the bridge officials were steadfast in their confidence in the structure.
THEORIES OF FAILURE Â¦
1. Random turbulence
2. Theory of Periodic vortex shedding
3. Theory of Aerodynamic instability
THEORY OF RANDOM TURBULANCE
An early theory was that wind pressure simply excited the natural frequencies of the bridge.This condition is known as Ëœâ„¢resonanceâ„¢â„¢.
THEORY OF VOTEX SHEDDING
The long standing theory behind the collapse
of the bridge was proposed by the leading
aeronautical engineer Theodore von KÃƒÂ¡rmÃƒÂ¡n, who
was on the committee set up to study the disaster. He
was convinced that the oscillations were due to the
shedding of vortices from the bridge. As air flows
round an object, swirls of air, called vortices, are
carried away by the wind. This is due to air at
different speeds combining.
The failure of the 1940 Tacoma Narrows Bridge and the success of the current Narrows bridge is a great American saga.
When Galloping Gertie splashes in to Puget Sound ,it creates ripples effect across the nation & across the world.
Collapse of the Tacoma bridge brought the engineering world to that the aerodynamic phenomena in suspension bridges were not adequately understood in the profession nor addressed in the design .
New researches were necessary to understand and predict the aerodynamic forces .
The official investigation in to collapse recommended the use of wind tunnel tests to aid in the design of vibration, aerodynamics,wave phenomena ,etc.