Posted on 08/02/2007 10:27:09 AM PDT by Lancey Howard
This was no slow collapse. It is horrifying.
Click on the link above and follow to “VIDEO: Tape shows moment of disaster”
ping
That’s the crappiest page I’ve seen. Keep tryin to do the video but just keep gettin’ run in circles on the page.
I had to un-block pop-ups, then click on the video.
Here, too:
http://www.cnn.com/video/#/video/us/2007/08/02/vosli.mn.i35w.bridge.collapse.side.view.cnn
The key here is that the North end collapsed first and brought the rest of the bridge down after. Also, a witness reported a “bang” and a plume of smoke before the collapse (reported by the guy who had gone under the bridge and 40 seconds later it collapsed. I suppose the bang could have been the North end landing on the ground and the plume was the dust seen in the video.
Using IE7 or Mozilla Firefox?........
Thanks.
Great screen name.
Try here, and scroll down on the left-hand side:
http://www.comcast.net/news/index.jsp?cat=GENERAL&fn=/2007/08/02/729846.html&cvqh=collapse_trapped
can you just bypass it by holding Ctrl while clicking on it?
Sorry... I got it. It was my pop up blocker... >blush<
Umm. Make that, “the right-hand side”. Sorry.
why do I care about a Bollywood reality show?
Computer illiterate here. It’s on my Google toolbar if that’s any help.
I only use my ‘puter for internet access and photography. (Windows XP)
Thank you for this excellent link.
Available FREE DOWNLOAD:
http://www.mozilla.com/
Yeah..that works too. Thanks for the tip.
Anyone heard any theories as to why the bridge collapsed? I always worry about maintenance when I cross a steel bridge. Rust does bad things to steel bridges that don’t get repainted frequently.
Something just gave completely away across the entire support structure close to the camera out of its view... there was no torquing of the deck, it just gave way.
CNN - I hate to admit they do anything right, but the picture is nice and big and there were no commercials.
Very enlightening - it does all seem to go at once - but the video doesn’t show the entire span - it makes me wonder if the part out of camera view went first or along with everything else. Hopefully some more videos from other angles will surface.
I wonder how long it will be before the leftie sites begin to report that “Jews were warned to avoid driving across the river,” and “everyone knows that it’s impossible for bridge girders fail.” And, of course there’s the old adage, “I question the timing...”
/s
I learned something important from your post:
Never, never, NEVER get Comcast.
One witness said a construction worker was using a jackhammer when she saw the collapse begin near that spot.
oops truncated... waiting for first enlightened lib to say this was globalwarmingclimatechange and somehow blame the whole thing on bushrovecheney. And people will buy it, big-time.
The most interesting view is the third loop on the CNN link - it shows a moment or two before any motion is detectable - but then the motion starts so quickly - one thing you can see very early is the steel radically deforming (like it’s made of rubber) near the south bank - but no way to know if that’s cause or effect...
The 3-D Rendered View of the Collapse on that Comcast website is amazing.
It was depended on four pylons; two on each side of the river with a steel superstructure tying the length together in somewhat the same manner that the string webbing creates the shape of an ordinary bag that you find potatoes in your market packaged.
In these and other photos, two pylons and their supports are still standing after the collapse on one river edge while only a partial piece of one of the pylons is visible on the opposite river edge.
The failure of the now missing pylon began a shearing motion which stretched and tore the steel from under the concrete roadway as it fell, pulling the remaining fallen sections with it as it plunged 750 feet to the water below.
If I’m not mistaken, and I rarely am, jackhammers generate heat—plus vibration . . . again perfect storm scenario. They had been jackhammering all day for a resurfacing project.
You can see the deflection occurs first (by just an instant) on that side, and that side strikes the water first as well. So — there was some major structural failure at that location, releasing collapsing forces that pulled everything down immediately with it.
...if they hit a resonant frequency then it was bound to fail either causing damage or destruction.
“Resonance frequency measurements are a major concern to materials, civil and aerospace engineers as well as others who work with structures. If a resonance frequency is too low, natural vibrations caused by wind or people walking can destroy the structure. The classic example of this is the Tacoma Narrows Bridge which was torn apart in a 42 mph wind storm.”
“...Measuring the resonance frequency of a structure is more difficult but, as the Tacoma Narrows Bridge illustrates, very important. There are a variety of physics based computer simulations of varying complexity that can model the structure. One of the big problems is taking into account all the materials that go into a structure like a building (stone, steel, aluminum, carpeting, etc.). For relatively simple structures such as truss bridges made from steel and concrete there are very good models used by civil engineers to use. Considerable advancements in modeling the response of more complex structures such as skyscrapers to wind are also being made. The American Society of Civil Engineers is a good source for further information.”
Backed up traffic would have caused a heavier load than normal. Jackhammer work might have matched the natural frequency of the bridge, though jackhammers would probably operate at a much higher rate than the structural frequency of the bridge. A harmonic might have matched, however.
These factors could not have caused a sound bridge to collapse, however. They might account for when the bridge collapsed (as opposed to why).
Do you have a link for that?
Thanks
Try this..... Bridges have expansion joints that allow the stucture to move as it thermally expands and contracts.
The expansion is a direct function of the heat and the expansion will be the temperature rise (delta T) times the coefficient of thermal exoansion = linear expansion along the span.
If over time the expansion joints somehow narrowed by being filled with noncompressable debris, the expansion would overstress some joint and pop..... or produce a loud bang.
Of course, the expansion joint could have been designed too narrow and produce the same effect.
Looking at the CNN photo album, you can see that the south end ramp did twist and tilt to one side, and I believe this was the original failure. The north end collapsed like a house of cards in response to the free fall of the main span after it became detached at the south end, just out of view of the video.
I am speculating that the loaded concrete mixers which are extremely heavy with a full load of concrete may have contributed to inducing an unknown variable in wave harmonics or inducing a wave.
I have been posting this because I really do have some serious background on that theory.
Firstoff I am not an armchair general or looking for popularity.
Its BECAUSE I am a supervisor at a concrete batching facility in central Alaska with 12 years experience of driving concrete mixers. This spring I was on a bridge of two lane that is approximately the same length and design as the I35 near Talkeetna, Alaska, the supervisor of the earthquake improvement project notified me my concrete was too “dry” or stiff and asked me to reslump it by adding water and re-mixing it at high speed for several minutes.
The result immediately felt was like being on a suspension pedestrian bridge and jumping up and down, the whole bridge was actually bouncing, everyone thought it was an earthquake which we have a lot of but it was too coincidental with what I was doing at the same time.
I saw on some video what appeared to be several even larger concrete mixers on the bridge, could this have contributed to making the structure to start a destructive “bounce’?
Anybody seen the Mythbusters episode where they tested Teslas theory that a small simple oscillating device can shake a huge steel structure like the Carquinez Straits Bridge in the Bay Area of California? A weak link added with corrosion, weight on the bridge like slow moving traffic on one side with construction equipment on the other with jackhammers and all this was probably never figured into the original design specs 40 years ago especially without computers or simulation models.
Other than sabotage and terrorist I believe I have a working theory, there could be still another variable like a weak base at the kingpost and it shifted.
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