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Old 6th September 2007, 09:50 PM   #1
Jonnyclueless
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Waiving the hands of physics

http://impactglassman.blogspot.com/2...cs-of-911.html

I am curious what some of the engineers in here think of the claims being made in this article. I can't imagine this hasn't been discussed on here, but i'll be darned if I can find it in the search engine. So please don't give me too many lashes if it has been and point me to the right thread. Thanks!

:-)
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Old 6th September 2007, 09:57 PM   #2
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Originally Posted by Jonnyclueless View Post
http://impactglassman.blogspot.com/2...cs-of-911.html

I am curious what some of the engineers in here think of the claims being made in this article. I can't imagine this hasn't been discussed on here, but i'll be darned if I can find it in the search engine. So please don't give me too many lashes if it has been and point me to the right thread. Thanks!

:-)
I haven't seen this one before, but the writer recycles a lot of claims -- the "2000% overdesign" (which only applies to live loads, and only on the perimeter columns, i.e. much less impressive than it sounds), the claim that the first floor collapse would be gradual, the claim that all failing structural members would have to fail simultaneously, and a half-baked rehash of Gordon Ross's energy absorption argument.

Since he appears to respect peer review, the best solution would probably be to confront him with Bazant, Le, Greening, and Benson, in press.

I'll be out for the next few days. Plenty of folks here are more than able to comprehensively take this guy apart. I'll be back in the off-chance there's anything left.
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Old 6th September 2007, 10:24 PM   #3
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Thanks Mackey

This part interests me the most:

"Well, to have such a small value of dt would require that the bottom of the falling “upper block” meet the floor below without the slightest tilt. For example, accepting Dr. Garcia’s free-fall speed calculation of 7.7 meters/second, tilting of a 63.4-meters-on-an-edge WTC floor by mere 1 degree would increase dt from his guesstimate of dt = 0.01 second all the way to dt = 0.14 second, giving the instantaneous total force of the falling “upper block” on the lower structure of just 1.3 times the static weight of the “upper block” instead of the 6.1 times as estimated in his “example.”

is this pointing out an error on Manuels part, or is he incorrect somehow...
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Old 6th September 2007, 10:34 PM   #4
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Originally Posted by Jonnyclueless View Post
Thanks Mackey

This part interests me the most:

"Well, to have such a small value of dt would require that the bottom of the falling “upper block” meet the floor below without the slightest tilt. For example, accepting Dr. Garcia’s free-fall speed calculation of 7.7 meters/second, tilting of a 63.4-meters-on-an-edge WTC floor by mere 1 degree would increase dt from his guesstimate of dt = 0.01 second all the way to dt = 0.14 second, giving the instantaneous total force of the falling “upper block” on the lower structure of just 1.3 times the static weight of the “upper block” instead of the 6.1 times as estimated in his “example.”

is this pointing out an error on Manuels part, or is he incorrect somehow...
I really don't understand the necessity of wasting time refuting such obviously woo ideas with real science. Woo deserves to be treated with mo more than scorn.

ETA - The quote in my signature puts it a bit more eloquently.
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Old 6th September 2007, 10:40 PM   #5
Jonnyclueless
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Could you do it for me? I don't speak the lingo.
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Old 6th September 2007, 10:58 PM   #6
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Originally Posted by Jonnyclueless View Post
Could you do it for me? I don't speak the lingo.
do what?
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Old 6th September 2007, 11:17 PM   #7
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Waste time refuting such Woo ideas with real science.
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Old 6th September 2007, 11:56 PM   #8
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What a horrifyingly boring read...

He spends 7 paragraphs telling us how awesome (his degree, his number of published papers, his "hirsch score") he is complete with allusions to Einstein (albeit stopping short of comparing himself to him)... and then in chapter err.. paragraph 8 he brings up 'proof by intimidation'. Ha ha! Classic!

He spends the next 6 paragraphs bemoaning how Garcia hasn't done any physics (for those keeping track at home, he hasn't either).

Then he spend 3 paragraphs crapping on Occam's razor... always something we want from our scientists...

About 15 paragraphs in he hasn't said anything. I'm already bored to tears.

Maybe I can finish reading it soon.
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Old 7th September 2007, 12:46 AM   #9
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Originally Posted by Jonnyclueless View Post
Waste time refuting such Woo ideas with real science.
Read my signature then you'll know my answer.
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Old 7th September 2007, 02:40 AM   #10
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Originally Posted by Jonnyclueless View Post
Thanks Mackey

This part interests me the most:

"Well, to have such a small value of dt would require that the bottom of the falling “upper block” meet the floor below without the slightest tilt. For example, accepting Dr. Garcia’s free-fall speed calculation of 7.7 meters/second, tilting of a 63.4-meters-on-an-edge WTC floor by mere 1 degree would increase dt from his guesstimate of dt = 0.01 second all the way to dt = 0.14 second, giving the instantaneous total force of the falling “upper block” on the lower structure of just 1.3 times the static weight of the “upper block” instead of the 6.1 times as estimated in his “example.”

is this pointing out an error on Manuels part, or is he incorrect somehow...
Notice how he fails to mention that a tilting upper block would bring the edges of the perimeter columns straight down into the 100psf-rated floorslabs of the lower section, slicing through them like a hot knife through butter.
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Old 7th September 2007, 04:15 AM   #11
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Originally Posted by Jonnyclueless View Post
http://impactglassman.blogspot.com/2...cs-of-911.html

I am curious what some of the engineers in here think of the claims being made in this article. I can't imagine this hasn't been discussed on here, but i'll be darned if I can find it in the search engine. So please don't give me too many lashes if it has been and point me to the right thread. Thanks!

:-)
A few things strike me as dishonest about this article, after wading through the initial disjointed and irrelevant rants. Firstly, the author's dismissal of Occam's razor is very carefully misleading. Let me explain.

Formulating a scientific theory generally proceeds from a series of observations, through formulation of the simplest hypothesis that can explain the observations, testing of the hypothesis with planned experiments or further observations, then refinement of the hypothesis if necessary to incorporate further observations. When that cycle has been run through enough times that no refinement is necessary, one has a useful theory.

Did you spot where Occam's razor came in there? Look after the first comma. It's not a case of generating lots of different hypotheses, evaluating each one, and choosing the simplest; it's about setting out in the first place to generate the simplest hypothesis, then only to complicate it if necessary to explain observations. So when Griscom gives his 1-0 score against Occam, he is effectively ignoring every time he has used Occam implicitly rather than explicitly. I suspect he's probably intelligent enough to realise that. Not a very good reflection on his intellectual honesty.

Comments on Garcia quoting a value to two significant figures are simply poisoning the well. But let's go on and look at Griscom's calculation of the loading for a 1 degree tilt, which he says will only give a 1.3 times excess over the static weight of the falling block. All very well, but what Griscom doesn't point out is that, if the falling block rotates, then the initial impact will be occur not across the whole structure. Instead, it will occur over a very small part of it, which will have far less ability to resist the impact. In fact, an energy calculation (comparing the gravitational potential energy liberated by a fall of one storey with the energy required to fracture the beams in the storey below) will show that these two effects precisely cancel each other. By only looking at one side of the equation, Griscom is deliberately misleading the reader on this point.

The 2000% live loadings comment has already been dealt with; the live loading of the structure is not its total weight, only the removable weight - furnishings, fixtures and occupants - so without an understanding of the ratio between live and dead weight in the structure it's meaningless (something I might forgive a fellow physicist for not knowing, but not for not trying to find out).

Finally, the comment that
Quote:
"if some steel columns simply refused to bend or break at the same time, the “upper block” would have descended those 3 meters without picking up nearly as much speed"
is simply laughable. How does Griscom propose that this could happen? How could the upper block fall three meters while some of the columns holding it up remain unbent and unbroken? This is a steel framed building, not a mesh of rubber bands. Quite simply, as soon as enough columns have failed that the remainder do not have enough strength to hold up the upper part of the building, the remaining columns must fail almost simultaneously, not by coincidence (as Griscom disingenuously suggests), but simply by geometry.

Overall, nothing to see here; Griscom's arguments are fatally flawed.

Dave
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Old 7th September 2007, 09:57 AM   #12
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PhD's in Physics just aren't the same as a degree in engineering and this article shows this to be the case.

The 2000% live load mistake has been highlit already and that is his big mistake. Another seems to tbe his notion that the remaining steel beams would fail slowly. If the Ultimate Tensile Strength of steel is exceeded the steel will fail quite quickly. Having actually witnessed this in an Instron, steel fails abruptly.

I hope someone points out the "live" load error.

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Old 7th September 2007, 10:44 AM   #13
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Griscom is a thorough toad whose real claim to fame in the 9-11 Denial movement is that he has staked out the single most offensive theory (download the PDF file) among all the crackpots: The "All Passengers Survived and Got Swiss Bank Accounts Theory".

Quote:
I envision a similar (to Operation Northwoods) 9/11 scheme, but one where the passengers boarded under their own names... I extend my "all passengers survived postulate to all four 9/11 "hijacked" flights on the notion that this small number of passengers might have been considered by conspirators as the minimum number for public credulity, while at the same time not exceeding the maximum number of "true believers in the cause" willing to accept long separations from their loved ones (sweetened by handsome Swiss bank accounts).
As I put it at SLC, Dylan Avery may not be the most sensitive person, but this guy makes him look like Richard Simmons.
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Old 7th September 2007, 10:54 AM   #14
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Originally Posted by Brainster View Post
Griscom is a thorough toad whose real claim to fame in the 9-11 Denial movement is that he has staked out the single most offensive theory (download the PDF file) among all the crackpots: The "All Passengers Survived and Got Swiss Bank Accounts Theory".



As I put it at SLC, Dylan Avery may not be the most sensitive person, but this guy makes him look like Richard Simmons.
I still say that refuting their idiot science with real science does nothing but lend credibility to theeir crackpot science and at worse some people instead of listening say "there must be something otherwise they wouldn't try so hard to refute them." Yes when we all argue and point out their inconsisitancies and logical fallacies "fencesitters" tend to see the truthers arguments are lacking in any substance but fighting their pseudoscientific bs with real science I am afraid will do the opposite.
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Old 7th September 2007, 10:55 AM   #15
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The worst mistake all these woo's make IMHO, is to assume that the falling upper block will be impacting the vertical structural members that constitute the system that takes the combined vertical load of the building.

It won't! It will hit the floor spans, the floor spans were most certainly never designed to support a load equal to the upper several stories of the structure let alone 1.3 times it. EVEN IF the upper block had settled slowly down on the next floor the building would have collapsed since the mass of the upper block is now primarily on the floor span rather than the columns. The floor fails and the upper block falls further, if it retains any velocity of its original fall then the next floor down will be even less able to arrest collapse.
The columns are also not simply having the upper block slide past them. They are being buffeted by the debris of the upper block.
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Old 7th September 2007, 04:58 PM   #16
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Well, we can't rule out magic.
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Old 7th September 2007, 05:02 PM   #17
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Or aliens, Johnny. Or sasquatch attack. Ghosts. Telekinetic assaults. Power of prayer. Bad feng shui.

I refuse to rest until these alternatives are thoroughly investigated!
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Old 7th September 2007, 10:23 PM   #18
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Originally Posted by ~enigma~ View Post
I still say that refuting their idiot science with real science does nothing but lend credibility to theeir crackpot science and at worse some people instead of listening say "there must be something otherwise they wouldn't try so hard to refute them." Yes when we all argue and point out their inconsisitancies and logical fallacies "fencesitters" tend to see the truthers arguments are lacking in any substance but fighting their pseudoscientific bs with real science I am afraid will do the opposite.
I tend to disagree with this sentiment, though I respect your approach as part of what is necessary overall.

My thought is that what is required is really a multi-layered approach to refuting this sort of nonsense, consisting partly of scorn and ridicule, when appropriate, but also having a measure of logic and fact and, dare I say it, "common sense" - things your average layperson can relate to easily. Still further it's helpful to have some real science behind all of this, which can be used as a reference and cited as a source, if people need more in-depth analysis to be persuaded.

Each of these methods has its own strengths and weaknesses, but, if used in concert, they will support each other, as one will succeed where another fails. And, in my opinion, that's more or less what we've got going on here. That's one reason why I enjoy reading and posting at these forums.
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Old 9th September 2007, 05:14 AM   #19
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Well, I posted a comment on Dr. Griscom's blog, as "ron", but I think the only ones paying attention to that blog entry now are JREFers, thanks to this thread.

Originally Posted by jaydeehess View Post
The worst mistake all these woo's make IMHO, is to assume that the falling upper block will be impacting the vertical structural members that constitute the system that takes the combined vertical load of the building.

It won't! It will hit the floor spans, the floor spans were most certainly never designed to support a load equal to the upper several stories of the structure let alone 1.3 times it. EVEN IF the upper block had settled slowly down on the next floor the building would have collapsed since the mass of the upper block is now primarily on the floor span rather than the columns. The floor fails and the upper block falls further, if it retains any velocity of its original fall then the next floor down will be even less able to arrest collapse.
The columns are also not simply having the upper block slide past them. They are being buffeted by the debris of the upper block.
I agree; the forces that acted upon the vertical supports weren't simply straight down. Since the collapse initialized on one side of the building, the upper block rotated as it started to fall, impacting the vertical supports at an angle. If you ever hear twoofers comment about material being thrust out (horizontal forces coming from explosives!!11!), you might ask if they considered that the impacts coming from an angle produce a horizontal component.
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