I think I heard about Randi Rhodes from (dead )Air America that she was blaming Bush. That's how the chickens come home to roost.
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General discussion
Bridge collapse probe focuses on unexplained shift
Maybe NOT Bush's fault after all? Maybe not time to panic after all?
MINNEAPOLIS, Minnesota (CNN) -- Investigators trying to figure out what caused Wednesday's massive bridge collapse are focusing on the southern end of the span, which "behaved differently" as it fell, the National Transportation Safety Board said Friday.
The NTSB, which is investigating the disaster that killed at least five people and injured dozens, is also hoping another video provided by the Army Corps of Engineers will provide new images of the collapse.
What's getting investigators' attention is the way the southern part of the bridge fell in a video they've already examined -- recorded by a security camera near the bridge's north end -- and the way the section settled after the collapse.
"It appears that it has shifted approximately 50 feet to the east and when we compare that to what we've seen in the rest of the bridge -- the rest of the bridge appears to have collapsed in place, " said NTSB Chairman Mark Rosenker, who is leading a 19-member team charged with determining the cause of the accident.
"We're going to take a look at any unique design factors that could have created that shift...for whatever reason."
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at the time of the collapse. I have to wonder if its rumbling near support structures will be considered a possible trigger. Trains make the ground shake around them.
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might have played a role. What would be particularly stressful would be if the frequency from the jackhammers happened to be the same as the frequency from the train. Such hHarmonic vibrations" are often a problem in amplyifying stress synergistically; that's why marching troops always break cadence when crossing a bridge.
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I have heard the tale of Marching troops breaking cadence on a bridge and wondered about it. Researching it all I was able to find for it's start was the case of the Broughton Bridge in 1829 which some blamed on marching troops.
Getting more current in the case of harmonic vibrations and bridge disasters there is the case of the Tacoma Narrows Bridge collapse in 1940 (AKA Galloping Gertie). Those two cases do have something in common, they were both suspension bridges. But in the case at hand the bridge was not a suspension bridge.
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As I recall, way back in the military days, troops were ordered to "extend ranks" and march "at ease" on a bridge structure, deliberately breaking cadence to preclude the "weight and vibration" of simultaneous pounding feet.
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maybe it was one of the History TV channels, or A&E, some time back in one of their hour long programs concerning bridges said it was discovered that the Tacoma 1940 'Galloping Gertie' was a design flaw that engineers did not know about at that time. The structure under the road surface of the bridge would catch the wind a certain way and the 'galloping' would start. All bridge designers learned from that experience and designed a different under structure for suspension bridges.
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IF the sub-structure support on the east side failed, tipping the structure to the east, forcing the remaining stronger sub-structure to "lean" to the east would account for such a "shift".
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