Debunking "physics by experts"

[GregoryUrich]

Actually, I was pointing out that after things stopped bouncing around, the building gained the mass of the loaded airplane at a distance of some 70-80 stories up, which would no doubt exceed the maximum floor loading--at least locally, even accounting for the spills and parts exiting the other side of the building. This favors collapse, quite strongly...

I said I wouldn't be reponding further on this thread, but this one is too dumb to let go. The reserve in the live load according to NIST was at least 1.0E6 kg per floor. Each floor could have held the weight of at least seven airplanes and the debris was spread over more than one floor.

[rwguinn]

I said I wouldn't be reponding further on this thread, but this one is too dumb to let go. The reserve in the live load according to NIST was at least 1.0E6 kg per floor. Each floor could have held the weight of at least seven airplanes and the debris was spread over more than one floor.

Reading comprehension bothering you again?
What do you think "Locally" means?

[Furcifer]

I said I wouldn't be reponding further on this thread, but this one is too dumb to let go. The reserve in the live load according to NIST was at least 1.0E6 kg per floor. Each floor could have held the weight of at least seven airplanes and the debris was spread over more than one floor.


Despite your disclaimer, you still warrant the "Drama Queen Award" for your exit from the thread and subsequent re-entrance. :)

That's actually closer to 10 airplanes from what I gathered from the Boeing site (110000 KG). Seems like a lot of weight IMO. I'm not saying you are right or wrong on this, I'm just saying if this is correct the floors were much stronger than I had imagined. You have to admit, 10 757's parked on the 78th floor puts this into perspective!

[shagster]

Purdue has done some work regarding the effect of the fluids on the structural damage. There are some visualizations on this site.

http://www.cs.purdue.edu/homes/cmh/simulation/phase3/

[shagster]

ftp://ftp.ecn.purdue.edu/sozen/OHIO/

ftp://ftp.ecn.purdue.edu/sozen/

http://www.cs.purdue.edu/cgvlab/papers/popescu/

http://www.cs.purdue.edu/cgvlab/papers/pop...agonVIS2003.mpg

[shagster]

Here's the clip of the fuel visualization so you don't have to download a 124MB clip.

http://s134.photobucket.com/albums/q91/shagster31/video/?action=view&current=db361b65.flv

[R.Mackey]

Actually, I was pointing out that after things stopped bouncing around, the building gained the mass of the loaded airplane at a distance of some 70-80 stories up, which would no doubt exceed the maximum floor loading--at least locally, even accounting for the spills and parts exiting the other side of the building. This favors collapse, quite strongly...

I said I wouldn't be reponding further on this thread, but this one is too dumb to let go. The reserve in the live load according to NIST was at least 1.0E6 kg per floor. Each floor could have held the weight of at least seven airplanes and the debris was spread over more than one floor.

I have to side with Gregory on this one, albeit for a more carefully considered reason. The local additional load caused by the weight of the 767 will be comparable to, but considerably less than, the wing loading of the intact aircraft, which works out (http://aerospaceweb.org/aircraft/jetliner/b767/) to 129.5 psf (632 kg / m2) at max gross TO weight. Since the aircraft debris was spread over three floors, I'd eyeball the load at no more than 25 to 10 psf. This is well within the reserve capacity of the structure. Might accelerate the collapse, and it does contribute to the gravity load, but it's not a dominant factor.

I believe NIST stated that they also did not consider the added weight significant, but I'm having trouble remembering where I saw it. I could be mistaken.

[Furcifer]

When I was thinkng localized I was thinking of the mass collecting on the wall face opposite the impact. I think if you consider it localized to one side, and that the floors/trusses were damaged the PE is a little more significant. Of course this is speculation on my part.
I assume Mackey that you distributed the mass evenly over 3 completely intact floors to come up with 10-25 psf?

[rwguinn]

I have to side with Gregory on this one, albeit for a more carefully considered reason. The local additional load caused by the weight of the 767 will be comparable to, but considerably less than, the wing loading of the intact aircraft, which works out (http://aerospaceweb.org/aircraft/jetliner/b767/) to 129.5 psf (632 kg / m2) at max gross TO weight. Since the aircraft debris was spread over three floors, I'd eyeball the load at no more than 25 to 10 psf. This is well within the reserve capacity of the structure. Might accelerate the collapse, and it does contribute to the gravity load, but it's not a dominant factor.

I believe NIST stated that they also did not consider the added weight significant, but I'm having trouble remembering where I saw it. I could be mistaken.

On reconsideration, I have to agree with you. ITdoes appear to be pretty minor, and even if all the remaining mass concentrated in the middle of a span, it would not be a large factor in the overall picture. And GregoryUrich--I was not picking on you specifically--I was pointing out that there was additional mass in the building. The fact that it did not cause immediate collapes is an indicator that it was not a major factor, and as RMackey pointed out, even NIST ignored it pretty much. But, since everybody seems to think "leaving no stone unturned" should include looking under every mouse dropping, too--I want to make sure that no detail is omitted.

[furrod]

Somewhat OT. These guys appear to be spewing the same old stuff. I'll just post the link if anyone wants to set them straight. I've got to admit, it's great theater when you guys hammer these idjits.


http://www.amazon.com/WTC-and-the-911-Conspiracy/forum/Fx1S3QSZRUL93V8/Tx2ISFYQ0SUI3C/1/ref=cm_cd_pg_oldest/102-7772207-6231313?%5Fencoding=UTF8&cdSort=newest

[shagster]

A study of lightweight floor trusses was done by by S.K. Choi, I.W. Burgess, and R.J. Plank,'The Behaviour Of Lightweight Composite Floor Trusses' (it's on the web somewhere and worth reading). Their model showed that extra loading of about 0.9 kN/m2 had little effect on the sag rate of the trusses much, but the temperature of the trusses had a very large effect. The ability of the aircraft debris, jet fuel, explosion/conflagration, and vibrations to remove insulation from the trusses and the subsequent fires are expected to have a far greater effect on truss sag than the extra weight of the aircraft in the building.

A 767-400ER has an empty mass of about 1E5 kg. The WTC tower had a footprint of 4020 m2. If I did the math right, that gives a load of about 0.25 kN/m2 if the mass of the aircraft was spread out over one story. That's about one-fourth of the extra load of 0.9 kN/m2 that Choi et al used in their model to see the effect of extra load on truss sag. If all of the mass of the aircraft was spread over a quadrant of a single story, it would be about 1 kN/m2.

From the Choi paper:

http://i134.photobucket.com/albums/q91/shagster31/papers/Choi1b.jpg

[Apollo20]

Shagster:

Finally a kindred spirit!

Have you tried to calculate the average mass of the aircraft fragments based on the information available in NIST NCSTAR 1-2B?

And how do the NIST and PERDUE simulations compare on this question?

Is it possible that the estimated fragment sizes are just a reflection of the "resolution" of the simulations?

[shagster]

Shagster:

Finally a kindred spirit!

Have you tried to calculate the average mass of the aircraft fragments based on the information available in NIST NCSTAR 1-2B?

And how do the NIST and PERDUE simulations compare on this question?

Is it possible that the estimated fragment sizes are just a reflection of the "resolution" of the simulations?


I haven't looked at those issues in detail. If I find anything else about them I will post it.

[Apollo20]

Thanks Shagster... By the way, on page lxviii of NIST NCSTAR 1-2B it is claimed that "the aircraft was broken into thousands of debris fragments..."

[Max Photon]

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If the jet broke into thousands of fragments, then one can imagine a frequency distribution by size of fragments.

I wonder what proportion of the mass of the jet would be within the size range one might consider "powder"?

Max

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[Apollo20]

Hi Max!

Good question!

But you know, for WTC 2 at least, an engine made it ALL THE WAY through the building.

Nevertheless, I am more interested in the fate of the aluminum fuselage and the possible degree of thermite sparking during the initial phase of the impacts...

Anyway, you are correct, we need the aluminum particle size distribution.

[David Wong]

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If the jet broke into thousands of fragments, then one can imagine a frequency distribution by size of fragments.

I wonder what proportion of the mass of the jet would be within the size range one might consider "powder"?

Max

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YOU JUST BLEW MY MIND.

[Apollo20]

David Wong:

So what do you think the aircraft aluminum particle size distribution was immediately after the impacts?

[Apollo20]

Gee, I thought that someone like GRAVY would have posted the official Al particle size distribution by now... After all it is 9:11 PM by my NIST atomic synchronized clock...

[Furcifer]

---

If the jet broke into thousands of fragments, then one can imagine a frequency distribution by size of fragments.

I wonder what proportion of the mass of the jet would be within the size range one might consider "powder"?

Max

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I would be very surprised to see anyone come up with a reasonable estimate of this. It's no small task due to the chaotic nature of the impact. I would however suggest that any dust that was produced by the impact, most likely was consumed in the fireball. Apollo should be able to verify this or not, but I would think that the fireball was hot enough to burn any aluminum particles suspended in air. None of the dust produced in the collision would have had a chance to settle by the time the explosion erupted.

[Apollo20]

3bodyproblem:

This very topic is being discussed over at PhysOrg. The NIST supporters are arguing AGAINST the probability of any significant amount of aluminum combustion in the towers in the first few seconds after the aircraft impacts...

By the way, did you know Wierzbicki says this in his paper:

"It was hoped that pieces of the aircraft were retrieved from "Ground Zero" to find the average size of the fragments."

Does anybody have any information on this?

[T.A.M.]

Gee, I thought that someone like GRAVY would have posted the official Al particle size distribution by now... After all it is 9:11 PM by my NIST atomic synchronized clock...

NIST clock...did you lose your truther pocketwatch...lol

TAM:)

[Minadin]

I don't want to sound incredulous, so hopefully it doesn't come out that way, but it seems to me that it would be exceedingly difficuly to figure out the sizes of those aluminum pieces with any sort of accuracy. Are you talking about an average overall size? Or a range of sizes of the debris, with an estimate of what % of the mass fit into each category? I am thinking something along the lines of: "20% of the aluminum from the aircraft was broken into pieces of size range X to Y, whereas 30% was broken into smaller pieces, sized Y to Z" might be the best way to describe it, but I'm not sure what method would be best to determine the ranges and percentages, or what purpose it would serve specifically to know this.

[twinstead]

I would imagine that the average size of the fragments would be meaningless in an investigation unless a certain average size is expected in a crash of this type.

[R.Mackey]

3bodyproblem:

This very topic is being discussed over at PhysOrg. The NIST supporters are arguing AGAINST the probability of any significant amount of aluminum combustion in the towers in the first few seconds after the aircraft impacts...

By the way, did you know Wierzbicki says this in his paper:

"It was hoped that pieces of the aircraft were retrieved from "Ground Zero" to find the average size of the fragments."

Does anybody have any information on this?

Well, I guess you'd call me a NIST supporter, but I'd suspect there was some aluminum combustion either during or shortly after impact. The contact flash as the aircraft entered the structure would seem to prove this. It also seems clear that the destruction of the aircraft would be primarily erosive rather than discrete impact, so some "grinding" and thus aluminum flakes would be expected.

Hard to say how much was turned into tiny bits. I don't know, a few percent? There is also the aluminum cladding and other sources to consider. Could be hundreds of kilograms, maybe more, left in a burnable form. Not concentrated in any one spot, of course.

To my knowledge there are only a handful of aircraft fragments recovered. Most are small, like the mystery bracket (http://forums.randi.org/showthread.php?t=81911) discussed and identified here, but others included a somewhat intact engine core and about 20% of a main landing gear. I'm pretty sure that not enough was recovered to produce a breakdown of mass as a function of size, surely not good enough for a dust or flake estimate.

The NIST simulations are definitely not high enough resolution to give you dust models. (Compare to the fuel model which used 1 kg "parcels" -- or thereabout, I'm going from memory --as its minimum size.) The best one could do would be to consider discrete debris vs. column impacts as predicted in the model and try to estimate the average flake production of each. A few experiments with a gas-operated cannon and a fixed steel column would be in order, I think. Sounds like fun.

[Furcifer]

I think an average size would suggest how much energy was released during the impact. You could work backwards to verify the amount that probably went into the core, floors and exterior.

Apollo: I'm not sure what would constitute a significant amount. There should be a finite size of particle that would be oxidized instantly by the fireball. I'm guessing this would be dependant on the heat of the fireball? The leading edge of the fuselage, making contact with the exterior columns and severing them, may have been "vapourized" as well. I'm not really sure about what would happen during that process to be honest. The more I think about it though, the more I realize it may actually have been a significant portion of the aluminum consumed in this way. It's an interesting concept to consider.

[Furcifer]

A few experiments with a gas-operated cannon and a fixed steel column would be in order, I think. Sounds like fun.

I agree, NonDestructiveTesting is over rated. Where's Chainsaw when you need him? Seems like something right up his alley.