At least the failure caused engineers to rethink bridge design and consider aeroelastic effects and vortex shedding.
His estimate of $6mil appealed to the feds. The original design had an $11mil estimate.
If the Eldridge design had been chosen the bridge would still be standing.
Moisseiff worked on the Bronx Whitestone Bridge, designing 11′ solid I beams, which later had to be reinforced. He was chief engineer on the Manhattan Bridge, where he put the railway on the outside lanes, causing tbe bridge to lean 5′ on one side. He was consulted on the Golden Gate Bridge. His road decking had to be reinforced in 1954. He died in disgrace in 1943. Ironically an engineering award in his name is presented every year.
Gertie’s oscillations were eight longitudinally on tbe main span every minute.
Gertie’s remains were not pilfered; they were sold by the state and mostly melted down during WW2. Much of the 1943 Lower Liard River Bridge in British Columbia on the AlCan Highway was made from Gertie’s parts .
]]>A short explanation:
http://youtu.be/6ai2QFxStxo
A long explanation:
http://www.cedengineering.com/upload/Ethical%20Issues%20Tacoma%20Narrows.pdf
“…in the case of the Tacoma Narrows Bridge, there was no resonance. According to Farquharson, one of the main investigators of the cause of the bridge collapse, the wind was steady at 42 miles per hour and the frequency of the destructive mode was 12 cycles/minute. This was neither a natural frequency mode of the structure nor the frequency of blunt-body vortex shedding of the bridge at that wind speed (which was approximately 1 Hz). Thus it is improbable that the resonance with alternating vortices played an important role in the oscillations of the bridge.”
Ummm… you’re joking, right? Who in their right mind would drive across a bridge that has a wave that reaches up to TEN feet tall, much less any feeling of movement at all? I mean, maybe it was just the perspective of the time, but I can’t believe that the bridge, although supposedly safe, wasn’t immediately closed until they could figure out what was wrong. I just can’t understand how ten foot-tall bridge waves would be considered OK. Does the Golden Gate or any other large bridge noticeably move so much that the motorists can actually feel it?”[/quote]
I have also felt movement on the Lion’s Gate Bridge up here in Vancouver. I was stuck in traffic in the middle once, and I got quite motion sick. For someone who’s terrified of heights, it was definitely a white knuckle experience!!!
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