• posted on April 24, 2006, 10:30 am
Before anybody bashes me, I am not a conspiracy nut. I was talking to a friend the other night and we discussed this. I would like your input and expertise, thanks.
I have heard some say that World Trade #7 collapsed "at the speed of gravity" as opposed to having floor after floor pancake on themselves, which I gather would be slower. Is that correct?
I am not an architect or an engineer, so I was hoping that maybe some folks here could illuminate the subject. My point of view, as a layman, is that the building would not collapse so perfectly because of debris from the twin towers. Am I correct or is there a possible explanation that architecture people might be able to describe? Or other?

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• posted on April 24, 2006, 1:29 pm
uh oh... here we go again...

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• posted on April 24, 2006, 3:37 pm

Huh? Gravity is not a "speed" =:-p The acceleration due to Gravity is, on earth, if I remember correctly, 32 feet per second. Gravity has no "speed".
The rate ("speed") at which something falls is a function of its mass, air resistance, and any other intervening factors (such as pillars and their composition, and so on).
IOW, it seems to be a non-argument from the get-go. Sounds like the one "argument" is something along the lines of instantaneous vaporization :p . It makes no sense. Not to me, at least.

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• posted on April 24, 2006, 5:36 pm
Kris Krieger wrote:

You gave a speed, not an acceletation. Gravity acceleration is 32 feet per second per second, or about 980 cm/second/second. That's for values near the surface of the Earth...
R

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• posted on April 25, 2006, 11:09 pm

Yup, you're right, per second, per second.
The context implied near the surface of the earth (or at least, as the saying goes, close enough thereto for government work), since it was the WTC. Mass and distance from the center of that mass are part of the Gravity equations, tho' I can't remember at all any more what the accelertion due to gravity is for other planets.
I almost never use metric any more, haven't for some years, so I've unfortunately forgotten much of it :(

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• posted on April 24, 2006, 5:42 pm
Osiris88 wrote:

Once the floors start pancaking down, do you expect the next floor down to have a longer elapsed time to failure or shorter? Shorter of course. The perceivable change in acceleration, or slowing down of gravity forces due to resistance of the building's structure, is hardly something someone can look at and say, "Yep, that sure looks like around 10 meters/second^2."
R

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• posted on April 24, 2006, 9:16 pm
"RicodJour"

Unless there was greater and greater structural support at each consecutive floor below, which is not to necessarily say that this is or was the case.

Yes, there should be natural chaotic variability to mess with predicability, so I think pancaking buildings won't fall according to gravity alone. There'll be issues of syrup-consistency, which can often be correlated to its temperature and sugar content for example, as well as how much butter there is, how light and fluffy each cake is, and maybe even the angle at which the cook whacks the stack, and what he uses to do so, etc.. And speaking of stack-whacks, here's a little tune/video: http://www.sfu.ca/~rmacinty/wing.mp4 --Wing of The Plane, by Severed Heads

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• posted on April 25, 2006, 5:55 pm
Osiris88 wrote:

See http://wtc.nist.gov/pubs/WTC%20Part%20IIC%20-%20WTC%207%20Collapse%20Final.pdf
for a general overview of how WTC 7 collapsed.
It doesn't really make sense to distinguish between floor pancaking and global collapse, as buildings are not monolithic structures, but structures made up of separate of parts (columns, beams, struts, floors, cladding, etc.) Depending on the design, failure of any of the critical structural parts can cause partial collapse, partial pancaking, global collapse, global pancaking, or nothing at all.
WTC 7 was a particularly unique example because unlike the vast majority of other buildings, this building had a structural system that transferred load from the new building system to an existing structural grid of a prior building. See the above document. Just from the line drawings you should be able to grasp that WTC 7 had some particularly critical columns, unlike most other skyscrapers where there is some structural redundancy.
As for a 'neat collapse', most buildings will little structural redundancy, particularly in the center core, will collapse onto their own footprint. given the nature of their component construction. Large buildings don't act like trees.
Marcello

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• posted on April 26, 2006, 2:13 am

The other fires were likely electrical fires or fires caused by the extreme heat of the tower 1 collapse. As you say, the final reports don't conclude that the diesel fuel fire made any difference if it was even burning when the global collapse occured.

Yes, that's the likely major cause along with all the other weaknesses caused by the other fires... the structural collapse occured just as the tower 2 collapse happened. Extreme heat from the fires weakened major structural components. Also recall that the vibrations caused by the tower 1 collapse could understandably have loosened fireproffing and maybe even some structural connections.
here's another interesting report with really good structural analysis: http://tinyurl.com/4gabz

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• posted on April 26, 2006, 3:04 am
Pierre Levesque, AIA wrote:

??? If I recall WTC 7 collapsed 6-7 hours after both Twin Towers had come down, like 4 or 5 in the afternoon.
Reading the final reports of WTC 1 and 2 is very illuminating, and also depressing. Some rather astonishing details.
Marcello

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• posted on April 26, 2006, 2:19 am

Actually that's most unlikely as WTC7 is north of WTC1 and the first plane hit away from WTC7. When WTC2 was hit from the south, WTC1 sheltered WTC7 so no jet fuel could have "sprayed" WTC7 at anytime

That's why nobody can confirm that the diesel fuel was ever a cause of any fire in WTC7. ALL reports determine that the diesel fuel "could" have contributed to the fires.

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• posted on April 26, 2006, 12:53 pm

Yeah, I used to have a really good view of the towers and had a really good view of them coming down. By then everyone was on their rooftops following the action. I remember standing there with my binocs and seeing that gaping hole and telling my neighbors that the towers were going to come down because I knew how they were built... to give you an idea of how the whole event made people lose focus and reason, most thought that the NYFD would be able to get the fires out, others actually thought that if they fell, they'd fall like trees and might "hit us" even though we were 2 miles away, others thought there were 100000 people working at the WTC and they ALL perished when the planes hit... it was, needless to say, a crazy day, er, make that a crazy eon in NYC. Now it feels like it was decades ago - ancient history except for those little reminders that keep creeping in like that movie that just opened yesterday...