Some Calculations requested regarding why the towers upper portion did not slide off

[hellaeon]

Goodaye guys,

I have actually been debating this issue with someone, its good and formal at the moment but although the collapse is logical to me, he asserts he think that the towers should have arrested on the floors below or slid off!

Now stop laughing I know how stupid that is :D

http://www.911oz.com/forum/public/viewtopic.php?t=120&start=15&postdays=0&postorder=asc&highlight=

Can someone say like beachnut or mackey or one of you other maths genius lords provide some numbers as to

1) approximate weight of falling mass (wtc 1 and 2)
2) the consequential force once the mass starts to fall
3) the amount of force required to stop it (arrest it) from below
4) the amount of force needed to be applied to one side to force it to 'slide off' (lol)

hahaha
slide off, I know its stupid, just simple logical deducation of weights and size tell me why, but the numbers, even back of the envelope would be good. I actually think (without checking) even at 25 degrees, this is only for a second and once stuff breaks, it breaks. I should not even need to go to these lengths but hey, may as well. Helps me explain it better as well to others away from the net.

It has been discussed at times before so I will look to search the forum as well. If you can PM or even reply in this thread it would be appreciated.

Im not interested in a 'ooo look he said this now!' and post the responses from there in here kind of thread, more so a discussion as to the absurdity of this claim.

Thanks heathens

[CHF]

I asked some twoofers the other day how blocks of 50,000 and 120,000 tons could somehow slide/fall out of their footprints without a horizontal force acting on them.

"You don't need a horizontal force cuz a chair would fall over" was basically the answer I got.

[Gravy]

So, you want some calculations, do you? (Appendix II) (http://www.911-strike.com/BazantZhou.htm)

[hellaeon]

So, you want some calculations, do you? (Appendix II) (http://www.911-strike.com/BazantZhou.htm)


Thanks for the link, I'll try to make heads or tails of it. Just a quick read is shows it as brilliant. I like to defer my caution to reality and this backs me up.

[Corsair 115]

hahaha
slide off, I know its stupid...It's not just stupid, it's doubleplusstupid. Next time you chat with them throw in that Newspeak phrasing and see how they react... :D

[TruthSeeker1234]

I asked some twoofers the other day how blocks of 50,000 and 120,000 tons could somehow slide/fall out of their footprints without a horizontal force acting on them.

"You don't need a horizontal force cuz a chair would fall over" was basically the answer I got.

Well, that's not the answer you'll get from this truther.

The correct answer is that the upper portion did not "slide off" because most of it very rapidly turned into powder. What the upper portion would have done had it remained macroscopic is an interesting question, but purely academic.

Of course we need a horizontal force to explain how large building sections would end up 500 feet away, like, for instance, in the winter garden. That's not a question for you to pose to a truther, it is a question for the truther to pose to you.

Most of the twin towers turned into powder, and that steel which remained macro was thrown about in a radius far outside the footprint. I ask you, how could this happen, "without a horizontal force acting upon them"?

[CHF]

The correct answer is that the upper portion did not "slide off" because most of it very rapidly turned into powder.

Oh right - the Judy Wood laser beam. :rolleyes:

Thanks Ace.

[TruthSeeker1234]

We don't know how they did it. That doesn't change what we observe. Unless you think the videos of the towers are fake, then the upper portions turned mostly to powder.

[CHF]

We don't know how they did it.

Judy's laser beam! Duh.

[Corsair 115]

The correct answer is that the upper portion did not "slide off" because most of it very rapidly turned into powder. This is a rather imprecise statement. Define "most" to begin with. Does this turning into powder include the steel? Or just the concrete?

Most of the twin towers turned into powder, and that steel which remained macro was thrown about in a radius far outside the footprint. I ask you, how could this happen, "without a horizontal force acting upon them"?I ask you why on Earth do you think that, given the kind of chaotic collapse that the WTC towers exhibited, the debris would fall into a neat, little pile? Why is that your expectation? What do you base that expectation on? Why wouldn't debris be spread all around?

[TruthSeeker1234]

Those were CHF's words, not mine. Ask CHF.

[CHF]

Those were CHF's words, not mine. Ask CHF.

Excuse me?

[Corsair 115]

Those were CHF's words, not mine. Ask CHF.You seem to be confused. Your name is attached to quotes in my post. In fact, you repeated the same basic claims in several different posts.

[3bodyproblem]

We don't know how they did it. That doesn't change what we observe. Unless you think the videos of the towers are fake, then the upper portions turned mostly to powder.

I've kept my cool up until now, BUT ARE YOU INSANE! POWDER!?!?!? In what world does steel turn into powder in mid air? POWDER?!?! MOSTLY POWDER?!?! That was all video trickery or something, you just chalk it up to that and let us live in our fantasy world. Just sit there like the Cheshire Cat knowing the real truth and leave us to our demise. When the time comes I will be the first one to say "Hey we should have all listened to that TruthSeeker guy cuz he was spot on about everything, let's all make a golden statue of him so we can worship at his feet for all eternity". POWDER?!?!? What about dust? Was the damn thing "powderfied" or "dustified"?

[CHF]

Was the damn thing "powderfied" or "dustified"?

Ah, now you're getting it. :D

Ace is a Judy Wood fan. Yes, there are still a few of them left.

[Unfit4Command]

Well, that's not the answer you'll get from this truther.

The correct answer is that the upper portion did not "slide off" because most of it very rapidly turned into powder. What the upper portion would have done had it remained macroscopic is an interesting question, but purely academic.

Of course we need a horizontal force to explain how large building sections would end up 500 feet away, like, for instance, in the winter garden. That's not a question for you to pose to a truther, it is a question for the truther to pose to you.

Most of the twin towers turned into powder, and that steel which remained macro was thrown about in a radius far outside the footprint. I ask you, how could this happen, "without a horizontal force acting upon them"?

You mean the perimeter columns that fell over in large sections and struck buildings hundreds of feet away? Like this:
http://i190.photobucket.com/albums/z80/911pictures/Twin%20Towers/collapse/columnd.jpg

A path leading right up the the winter garden.

[3bodyproblem]

Ah, now you're getting it. :D

Ace is a Judy Wood fan. Yes, there are still a few of them left.

I've avoided TS because I can't take this level of absurdity. I thought pomeroo was being almost too harsh on him at times, but JC, he's just doing it to drive people crazy. POWDER! a building turned to powder?! Hey I have an idea, the building turned to powder. Marvin Martian used his friggin death ray and turned the damn thing to POWDER when no one was looking. They forgot to edit that out, although the mass hysteria has somehow allowed this little anomoly to go unnoticed by everyone else but him.

[BillyRayValentine]

Of course we need a horizontal force to explain how large building sections would end up 500 feet away, like, for instance, in the winter garden. That's not a question for you to pose to a truther, it is a question for the truther to pose to you.

Most of the twin towers turned into powder, and that steel which remained macro was thrown about in a radius far outside the footprint. I ask you, how could this happen, "without a horizontal force acting upon them"?

Watch this video from the 19:40 mark. You'll get a pretty clear picture of what happened during the collapse of wtc 1. Pay close attention at 19:46, when a 60+ section of the north facade peels away and heads toward wtc 7.

http://video.google.com/videoplay?docid=5474006551011489413&q=what+we+saw&total=15291&start=0&num=10&so=0&type=search&plindex=2

Hope that clears things up a bit for you. You seem very confused.

[XXX]

So, you want some calculations, do you? (Appendix II) (http://www.911-strike.com/BazantZhou.htm)

And if your truthers are anything like the ones I've been getting lately, they'll just respond by telling you that "Bazant has been debunked!" and then give you that link to that guy who scribbled his garbage all over his paper and pretend that's the end of it.

[Arkan_Wolfshade]

Truthseeker1234, I now dub you TruthseekerPU36

[WildCat]

I've avoided TS because I can't take this level of absurdity. I thought pomeroo was being almost too harsh on him at times, but JC, he's just doing it to drive people crazy. POWDER! a building turned to powder?! Hey I have an idea, the building turned to powder. Marvin Martian used his friggin death ray and turned the damn thing to POWDER when no one was looking. They forgot to edit that out, although the mass hysteria has somehow allowed this little anomoly to go unnoticed by everyone else but him.
Ace also refers to an 8 story high pile of rubble as a "crater". The man is not playing with a full deck, best to either humor him or ignore him.

[uk_dave]

And if your truthers are anything like the ones I've been getting lately, they'll just respond by telling you that "Bazant has been debunked!" and then give you that link to that guy who scribbled his garbage all over his paper and pretend that's the end of it.

Just tell them that the debunking has been debunked

[Lurker]

Most of the twin towers turned into powder, and that steel which remained macro was thrown about in a radius far outside the footprint. I ask you, how could this happen, "without a horizontal force acting upon them"?

Imagine a beam of steel and apply a moment at each end. Imagine then that each end fails catostropically such that the stored elastic energy of the bent beam is suddenly released. The beam will displace in a horizontal direction.

This is basic engineering concerning buckling and collapse. You can simulate this by taking something with a moderate elastic modulus and bending it between your thumb and forefinger and allowing it to slide off the fingers. Note how the sample flies outwards. Kids learn this trick at an early age. Why didn't you?

Lurker

[Alferd_Packer]

There is actually a new Bazant paper out there. I'd post a link to it, but I'm too new here.

Now as to why the towers didn't "slide off" it is simple. Before Marvin Bush left his job at t h security company, a year before 9/11, he snuck into the building and smeared contact cement all over the undersides of the floors.

[Alferd_Packer]

Pay close attention at 19:46, when a 60+ section of the north facade peels away and heads toward wtc 7.


And if you look really cloesly, you might even see the wires attached to that section where Silverstein is "pulling" it onto WTC 7. :)

This is called a "Beam" weapon

[CurtC]

I've kept my cool up until now, BUT ARE YOU INSANE! POWDER!?!?!? In what world does steel turn into powder in mid air? POWDER?!?! MOSTLY POWDER?!?!
You must have missed that other video, the one showing a tall section of core remaining standing, then falling, leaving a wake of dust. Ace declared that the solid steel core columns were actually turning to dust in mid-air, because they were no longer visible through the dust they left behind. It's pure insanity.

[1337m4n]

We don't know how they did it. That doesn't change what we observe. Unless you think the videos of the towers are fake, then the upper portions turned mostly to powder.

Um no. Stop making stuff up without supporting evidence.

[TruthSeeker1234]

I asked some twoofers the other day how blocks of 50,000 and 120,000 tons could somehow slide/fall out of their footprints without a horizontal force acting on them.

"You don't need a horizontal force cuz a chair would fall over" was basically the answer I got.

CHF, you are clearly implying that the towers fell into their footprints. You are deriding "twoofers" for a supposed lack of a mechanical explanation for how mass could "somehow slide/fall out of their footprints without a horizontal force acting on them".

The evidence is overwhelming. The great bulk of surviving tower mass landed well outside the respective footprints. It is gravity-collapse theorists who must supply a mechanical explanation for this. Truthers unanimously agree that some type of explosive(s)/weapon(s) were used to destroy the towers. Whatever had the energy to dissociate all those molecular bonds also had the energy to propel large portions of the walls sideways.

[Lurker]

Truthseeker,

I have already posted one mechanism for material being ejected sideways. Why do you ignore this simple and common mechanism?

Lurker

[Belz...]

I asked some twoofers the other day how blocks of 50,000 and 120,000 tons could somehow slide/fall out of their footprints without a horizontal force acting on them.

"You don't need a horizontal force cuz a chair would fall over" was basically the answer I got.

Yeah, or "tree". Anything made out of wood, works.

Except Ace, of course:

The correct answer is that the upper portion did not "slide off" because most of it very rapidly turned into powder.

Ace prefers impossible technologies to natural similes.

We don't know how they did it. That doesn't change what we observe.

Actually, it does, because you don't observe what the REST OF THE WORLD observes. Pity that doesn't ring any bells for you.

CHF, you are clearly implying that the towers fell into their footprints.

No, he's not. If you can't interpret what you see in a video correctly, why would we expect you to interpret what you read in a post correctly ?

[cmcaulif]

Goodaye guys,

I have actually been debating this issue with someone, its good and formal at the moment but although the collapse is logical to me, he asserts he think that the towers should have arrested on the floors below or slid off!

Now stop laughing I know how stupid that is :D

http://www.911oz.com/forum/public/viewtopic.php?t=120&start=15&postdays=0&postorder=asc&highlight=

Can someone say like beachnut or mackey or one of you other maths genius lords provide some numbers as to

1) approximate weight of falling mass (wtc 1 and 2)
2) the consequential force once the mass starts to fall
3) the amount of force required to stop it (arrest it) from below
4) the amount of force needed to be applied to one side to force it to 'slide off' (lol)

hahaha
slide off, I know its stupid, just simple logical deducation of weights and size tell me why, but the numbers, even back of the envelope would be good. I actually think (without checking) even at 25 degrees, this is only for a second and once stuff breaks, it breaks. I should not even need to go to these lengths but hey, may as well. Helps me explain it better as well to others away from the net.

It has been discussed at times before so I will look to search the forum as well. If you can PM or even reply in this thread it would be appreciated.

Im not interested in a 'ooo look he said this now!' and post the responses from there in here kind of thread, more so a discussion as to the absurdity of this claim.

Thanks heathens

In the newest paper from Bazant, Le, Benson, and Greening, they calculate the centroid of mass for the falling body, which is probably what you are looking for. Fig 2 on page 20:

http://www.civil.northwestern.edu/people/bazant/PDFs/Papers/00%20WTC%20Collapse%20-%20What%20did%20&%20Did%20Not%20Cause%20It%20-%20Revised%206-22-07.pdf

[bje]

We don't know how they did it. That doesn't change what we observe. Unless you think the videos of the towers are fake, then the upper portions turned mostly to powder.


Not THAT canard again.

There are NO videos showing the upper portions of either tower "turning to dust."

[e^n]

The evidence is overwhelming. The great bulk of surviving tower mass landed well outside the respective footprints.

Prove it, the only debris I see scattered outside the base of the towers seems to be perimeter column sections. There are very few identifiable truss sections and even less core columns. On what basis do you estimate the mass ejected and can you show me your calculations?

[nicepants]

We don't know how they did it. That doesn't change what we observe. Unless you think the videos of the towers are fake, then the upper portions turned mostly to powder.

Source for this claim?

[twinstead]

Please don't get truthseeker1234 started. That's all we need is another 50 page thread about how only he is able to see what really happened during the collapse, and all the experts and non-experts alike who watched the same videos are totally wrong (or worse, 'in on it')

[HeyLeroy]

Truthseeker1234, I've asked you this before but I forget whether you answered or not. Was Chuck Steven Jones lying when he disputed Woods?

As we examined the WTC-debris sample, we found large chunks of concrete (irregular in shape and size, one was approximately 5cm X 3 cm X 3cm) as well as medium-sized pieces of wall-board (with the binding paper still attached). Thus, the pulverization was in fact NOT to fine dust, and it is a false premise to start with near-complete pulverization to fine powder (as might be expected from a mini-nuke or a “star-wars” beam destroying the Towers). Indeed, much of the mass of the MacKinlay sample was clearly in substantial pieces of concrete and wall-board rather than in fine-dust form...

It seems that the 9/11 truth community likewise “has been slow to understand” that the WTC dust particles in greatest abundance are the “supercoarse” variety rather than “fine” particles, and that significant chunks of concrete were also found in the WTC rubble.
source (http://www.journalof911studies.com/letters/a/Hard-Evidence-Rebudiates-the-Hypothesis-that-Mini-Nukes-were-used-on-the-wtc-towers-by-steven-jones.pdf)

[GlennB]

Truthseeker1234, I've asked you this before but I forget whether you answered or not. Was Chuck Steven Jones lying when he disputed Woods?

And there's the quandry, in a nutshell.

Dealing with 9/11 Truthers is like getting toothpaste back in the tube. There's always another squirm going on over there.

It fell in its footprint??? CD !!!
It didn't fall in its footprint??? CD !!!

<etc etc, even unto the end of the world>

[Reality Believer]

And there's the quandry, in a nutshell.

Dealing with 9/11 Truthers is like getting toothpaste back in the tube. There's always another squirm going on over there.

It fell in its footprint??? CD !!!
It didn't fall in its footprint??? CD !!!

<etc etc, even unto the end of the world>

Yep, the red herring gets pretty deep sometimes. Instead of attempting to countering the argument. I think it would be appropriate to call the logical fallacy like it is and say NEXT.

[William Rea]

Goodaye guys,

I have actually been debating this issue with someone, its good and formal at the moment but although the collapse is logical to me, he asserts he think that the towers should have arrested on the floors below or slid off!

Now stop laughing I know how stupid that is :D

http://www.911oz.com/forum/public/viewtopic.php?t=120&start=15&postdays=0&postorder=asc&highlight=

Can someone say like beachnut or mackey or one of you other maths genius lords provide some numbers as to

1) approximate weight of falling mass (wtc 1 and 2)
2) the consequential force once the mass starts to fall
3) the amount of force required to stop it (arrest it) from below
4) the amount of force needed to be applied to one side to force it to 'slide off' (lol)

hahaha
slide off, I know its stupid, just simple logical deducation of weights and size tell me why, but the numbers, even back of the envelope would be good. I actually think (without checking) even at 25 degrees, this is only for a second and once stuff breaks, it breaks. I should not even need to go to these lengths but hey, may as well. Helps me explain it better as well to others away from the net.

It has been discussed at times before so I will look to search the forum as well. If you can PM or even reply in this thread it would be appreciated.

Im not interested in a 'ooo look he said this now!' and post the responses from there in here kind of thread, more so a discussion as to the absurdity of this claim.

Thanks heathens

Since you admit you don't have the maths and analysis etc (apart from some back of the envelope stuff) why do you conclude that you KNOW that the argument is logical and that the other explanation is stupid?

Can you describe the process of thinking (without checking)?

I am sitting here in awe of how you managed to make it this far without being torn apart by the logic hounds of JREF. Silly me, you're "skeptic" aren't you.

[CHF]

CHF, you are clearly implying that the towers fell into their footprints.

No, I'm saying that the top sections of the towers had nowhere to go but down when the collapse started.

[3bodyproblem]

No, I'm saying that the top sections of the towers had nowhere to go but down when the collapse started.

What? And totally rule out UP!

Don't laugh but I've got this debate going on over a ColbertNation with a guy who says the explosions sucked the building down at twice the speed they "should have" fallen (based on some paper a nutter over at scholars for truth has posted the collapse should have taken 25 seconds)

Nevermind, it's hysterical, go ahead and laugh.

[WildCat]

Imagine a beam of steel and apply a moment at each end. Imagine then that each end fails catostropically such that the stored elastic energy of the bent beam is suddenly released. The beam will displace in a horizontal direction.

This is basic engineering concerning buckling and collapse. You can simulate this by taking something with a moderate elastic modulus and bending it between your thumb and forefinger and allowing it to slide off the fingers. Note how the sample flies outwards. Kids learn this trick at an early age. Why didn't you?

Lurker
I've used the example before of hitting a nail slightly off center so that instead driving it into the wood it flys off in some direction. I think just about everyone has experienced this themselves, and that the same effect would be seen on a much larger scale from a ginormous (yes it's officially a word now!) building collapsing. But troofers don't seem to be able to grasp such a simple concept.

[William Rea]

Imagine a beam of steel and apply a moment at each end. Imagine then that each end fails catostropically such that the stored elastic energy of the bent beam is suddenly released. The beam will displace in a horizontal direction.

This is basic engineering concerning buckling and collapse. You can simulate this by taking something with a moderate elastic modulus and bending it between your thumb and forefinger and allowing it to slide off the fingers. Note how the sample flies outwards. Kids learn this trick at an early age. Why didn't you?

Lurker

It's probably not that people aren't aware of the phenomenon, it's just that the mechanism you describe appears irrelevant.

I'd like to see your data on how all this internal elastic strain energy is being transmitted and how it is being released.

[3bodyproblem]

I'd like to see your data on how all this internal elastic strain energy is being transmitted and how it is being released.

F= Fxsin(theta) + Fycos(theta)

[TruthSeeker1234]

No, I'm saying that the top sections of the towers had nowhere to go but down when the collapse started.

So tell me where the hat trusses and the the broadcast tower ended up.

And if it was a collapse, tell me why the top sections become half their height before the bottom sections move at all.

[BillyRayValentine]

And if it was a collapse, tell me why the top sections become half their height before the bottom sections move at all.

What is it that motivates a person to make claims that are blatantly contradicted by a mountain of evidence, including crystal clear videos? I really am baffled.

Whatever the source of your fearlessness, it seems to have affected your sense of shame as well.

[CHF]

So tell me where the hat trusses and the the broadcast tower ended up.

And if it was a collapse, tell me why the top sections become half their height before the bottom sections move at all.

I told you already: Judy Wood's laser beam dustified it.

[fitzgibbon]

What is it that motivates a person to make claims that are blatantly contradicted by a mountain of evidence, including crystal clear videos? I really am baffled.

Whatever the source of your fearlessness, it seems to have affected your sense of shame as well.

Big Lie© thinking, BRV. If typed (even by himself), it can be referenced back to as supporting 'evidence' even if proven wrong. As for shame, there's no sense; it's a learned behaviour which I have to presume TS1234 hasn't.

[Alt+F4]

I told you already: Judy Wood's laser beam dustified it.

Too bad Dr. Judy can't:
1. describe the weapon.
2. explain how it works.
3. understand how a kitchen microwave oven works.

But hey, who needs science when you have a cool word like dustification...

[HeyLeroy]

What? And totally rule out UP!
(snip)

C'mon, you know that in Michigan they call it "The Yoop".

So tell me where the hat trusses and the the broadcast tower ended up.

And if it was a collapse, tell me why the top sections become half their height before the bottom sections move at all.

Was Steven Jones lying?

[Newtons Bit]

So tell me where the hat trusses and the the broadcast tower ended up.

And if it was a collapse, tell me why the top sections become half their height before the bottom sections move at all.

That's actually fairly simple to understand. With the first impact of the upper block, the floors and trusses all expierenced a sudden impulse deacceleration. With f=ma, this force easily overcomes the connections of the floors to the columns. An equal and opposite force is applied to the lower block, however the energy required to detach the floors is much much less than the energy required to buckle columns. The floors detach and "free-fall". Each one hitting the floor below until there is sufficient mass and dynamic loading to cause the first columns in the upper block to fail. From there it's more of a standard pancake collapse.

[Corsair 115]

Too bad Dr. Judy can't:
1. describe the weapon.
2. explain how it works.
3. understand how a kitchen microwave oven works.I'd suggest a fourth question: 4) Explain when this weapon was put into orbit. I'd imagine such a weapon with such power would have to be considerably large device, and there aren't many launch vehicles in the U.S. inventory that can put large payloads into oribt.

I'm assuming of course that she says this weapon is in low Earth orbit. This raises its own problems since in LEO an object will not be spending very long over the same part of the Earth's surface.

[pomeroo]

[quote=Newtons Bit;2767597]That's actually fairly simple to understand.


If it has anything to do with real science, it isn't simple for Ace to understand.



][quote=Newtons Bit;2767597]
With the first impact of the upper block, the floors and trusses all expierenced a sudden impulse deacceleration. With f=ma, this force easily overcomes the connections of the floors to the columns. An equal and opposite force is applied to the lower block, however the energy required to detach the floors is much much less than the energy required to buckle columns. The floors detach and "free-fall". Each one hitting the floor below until there is sufficient mass and dynamic loading to cause the first columns in the upper block to fail. From there it's more of a standard pancake collapse.



Nope. It's turtles all the way down.

[pomeroo]

[quote=Corsair 115;2768105]I'd suggest a fourth question: 4) Explain when this weapon was put into orbit. I'd imagine such a weapon with such power would have to be considerably large device, and there aren't many launch vehicles in the U.S. inventory that can put large payloads into oribt.

I'm assuming of course that she says this weapon is in low Earth orbit. This raises its own problems since in LEO an object will not be spending very long over the same part of the Earth's surface.



The fifth question is the one Ace really dislikes:

Why are these super-weapons, which will not be available on Earth for decades, at the disposal of the Bush/Cheney crime family, WHILE THE MILITARY HAS NO ACCESS TO THEM? Where do they show up in the budget? Why don't any Democrats complain?

Ace's first and only hapless attempt to justify Judy's fairy tale was to pretend that Fetzer's imaginary 2.3 TRILLION dollars covered the costs of R & D.

Everyone laughed at him, just as they laugh at Fetzer.

[lozenge124]

That's actually fairly simple to understand. With the first impact of the upper block, the floors and trusses all expierenced a sudden impulse deacceleration. With f=ma, this force easily overcomes the connections of the floors to the columns. An equal and opposite force is applied to the lower block, however the energy required to detach the floors is much much less than the energy required to buckle columns. The floors detach and "free-fall". Each one hitting the floor below until there is sufficient mass and dynamic loading to cause the first columns in the upper block to fail. From there it's more of a standard pancake collapse.


Except that neither NIST nor the latest Bazant/Greening paper endorses the pancake collapse:
NIST’s findings do not support the “pancake theory” of collapse, which is premised on a progressive failure of the floor systems in the WTC towers (the composite floor system—that connected the core columns and the perimeter columns—consisted of a grid of steel “trusses” integrated with a concrete slab; see diagram below). Instead, the NIST investigation showed conclusively that the failure of the inwardly bowed perimeter columns initiated collapse and that the occurrence of this inward bowing required the sagging floors to remain connected to the columns and pull the columns inwards. Thus, the floors did not fail progressively to cause a pancaking phenomenon.
http://wtc.nist.gov/pubs/factsheets/faqs_8_2006.htm

In the structural engineering community, one early speculation was that, because of a supposedly insufficient strength of the connections between the floor trusses and the columns, the floors ‘pancaked’ first, leaving an empty framed tube, which later lost stability. This hypothesis, however, was invalidated at NIST by careful examination of the photographic record, which shows some perimeter columns to be deflected by about 1 m inward. NIST explains this deflection by a horizontal pull from catenary action of floor trusses as they sag due to differential thermal expansion as well as creep. Such action would have been impossible if the floor trusses disconnected from the perimeter columns.
http://www.civil.northwestern.edu/people/bazant/PDFs/Papers/00%20WTC%20Collapse%20-%20What%20Did%20%26%20Did%20Not%20Cause%20It%20-%205-2007.pdf

[William Rea]

That's actually fairly simple to understand. With the first impact of the upper block, the floors and trusses all expierenced a sudden impulse deacceleration. With f=ma, this force easily overcomes the connections of the floors to the columns. An equal and opposite force is applied to the lower block, however the energy required to detach the floors is much much less than the energy required to buckle columns. The floors detach and "free-fall". Each one hitting the floor below until there is sufficient mass and dynamic loading to cause the first columns in the upper block to fail. From there it's more of a standard pancake collapse.

Hold on, hold on. From what I have read this needs some work. Where is the data regarding the impulse force required to detach the undamaged floors in the upper block?

This impulse deceleration you talk about implies that the steel superstructure of the upper block does not "crumple" into that of the lower block (like the front end of a car in a crash). What you seem to be saying is that the steel superstructure comes to a sudden halt and the inertia of the floors means they detach and fall into the lower block (like the passengers getting thrown through the windscreen). If this is so then wouldn't we expect to see major evidence of destruction associated with relatively minor vertical movement of the outer steel superstructure. Is this the case?

[Revolutionary91]

Hold on, hold on. From what I have read this needs some work. Where is the data regarding the impulse force required to detach the undamaged floors in the upper block?

This impulse deceleration you talk about implies that the steel superstructure of the upper block does not "crumple" into that of the lower block (like the front end of a car in a crash). What you seem to be saying is that the steel superstructure comes to a sudden halt and the inertia of the floors means they detach and fall into the lower block (like the passengers getting thrown through the windscreen). If this is so then wouldn't we expect to see major evidence of destruction associated with relatively minor vertical movement of the outer steel superstructure. Is this the case?

I'm still waiting for a JREFer to explain this footage:

http://gordonssite.com/demolition/2003-0000.jpg

http://gordonssite.com/demolition/2003-0101.jpg

http://gordonssite.com/demolition/2003-0120.jpg

http://gordonssite.com/demolition/2003-0120-2.jpg


Dr. Bazant's theory tells us that the energy would concentrate in and crush the volume below the aircraft impact level.

These photographs clearly show that the first volume to be crushed was a volume of the upper section. Dr. Bazant has supplied us with a physical measure of the movement of the roof of the tower. He has asked us to believe that this acceleration of the roof line was the same as the lower end of the upper section, because the upper section remained whole and rigid. This is easily revealed to not be the case. Far from being a measure of the progress of the collapse front down the tower, it is actually a measure of the progress of the destruction of the upper section. The foundation of the entire argument can be undermined simply by showing one undeniable sequence of events.

http://www.911blogger.com/node/9154

[TruthSeeker1234]

Yes, I posted a similar graphic months and months ago, with no answer.

It was in my thread about "Dr. Greening Refuted Easily". Eventually in an email to me, Greening said that the walls in the upper block slipped inside of the walls of the lower block. LOL, that's what he said. I'm not sure if he still says that or not.

Greening also never answered me on why the smoke from the fires would go from dark black to white as soon as the towers "collapsed". I would think the fuel would be the same stuff, with less oxygen if anything.

[3bodyproblem]

I'm not sure about he rest of the "JREF'ers", but I agree with the notion that a volume of the upper section underwent progressive collapse as the lower section underwent progressive collapse. "Crushed together" for the first few seconds of collapse. I'm not sure what you hope to prove with this? At some point the upper section did get crushed, to treat it before , after or during the colpase of the lower does little to change the validity of the math involved. It just changes the density of the crushing front. I believe Bazant admits this in the BandV paper if I remember correctly.
What do you think it means Rev91?

[William Rea]

Yes, I posted a similar graphic months and months ago, with no answer.

It was in my thread about "Dr. Greening Refuted Easily". Eventually in an email to me, Greening said that the walls in the upper block slipped inside of the walls of the lower block. LOL, that's what he said. I'm not sure if he still says that or not.

Greening also never answered me on why the smoke from the fires would go from dark black to white as soon as the towers "collapsed". I would think the fuel would be the same stuff, with less oxygen if anything.

The walls were bowing inwards according to eye witness testimony so how did they slide inside?

[3bodyproblem]

Yes, I posted a similar graphic months and months ago, with no answer.

It was in my thread about "Dr. Greening Refuted Easily". Eventually in an email to me, Greening said that the walls in the upper block slipped inside of the walls of the lower block. LOL, that's what he said. I'm not sure if he still says that or not.

Greening also never answered me on why the smoke from the fires would go from dark black to white as soon as the towers "collapsed". I would think the fuel would be the same stuff, with less oxygen if anything.

I gave an answer.

What he says is correct to some degree, although I would allow for more crushing than slipping myself.

DUST. Almost positive on that since it "falls".

[3bodyproblem]

The walls were bowing inwards according to eye witness testimony so how did they slide inside?

Bowing in or bowing out they can slide inside.

[William Rea]

Bowing in or bowing out they can slide inside.

Were both the upper and lower blocks bowing?

[Newtons Bit]

Yes, I posted a similar graphic months and months ago, with no answer.

Yes, I posted an answer a few posts above but you seemed to not notice. Is the term, "eyes wide shut" appropiate?

Lozenge seems to think that by "more of a standard collapse" after the lower block hits means is somehow the same as the original FEMA idea. Which is of course the idea that the initiating collapse is caused by a floor slab slipping it's bolts. He didn't bother reading well enough to figure out that I was in fact talking about an even long after the initial collapse. This is a trait common to most truthers: take words out of context, if that's not possible, ignore.

[3bodyproblem]

Were both the upper and lower blocks bowing?

Before during or after collapse initiation? My understanding is the the floors pulled the exterior inwards at the point of impact, and only at initiation. After that neither were "bowing", although one section would have forced the other out of the way during impact. Either way, you can have the upper section getting tucked behind the lower during ythe collapse. I'm not a big fan of that analysis myself, but it is a valid consideration for the first few (2?) seconds of the collapse. It's certainly not an outrageous claim, I've heard worse. Those guys put more effort into the analysis than I have, so if push came to shove I would yield to them. I'm just not feeling it.

[TruthSeeker1234]

My thread was on Greening's paper. In it, he said there was a top block which remained intact until it "crushed down" through the lower building, all the way to the ground. Then (and only then), the top block itself underwent "Crush Up".

Greening has been forced to abandon this idea. How any honest person could have ever entertained it is beyond me, precisely because of observations such as are made in the graphic posted by Rev.

Currently Greening and Bazant have come up with "crush down crush up", which is still ludicrous. The "collapse" times require low resistance, pulverization requires high resistance (the resistance paradox).

This theory allows for (at most) about 20% of the mass of the towers to be ejected outside the footprint. This means that 80% or more would have to remain inside the footprint.

There is no evidence for this at all. I have requested at least a dozen times, and I will repeat the request now.

Please link us to any evidence whatsoever that 80% or more of the mass of each tower remained in the footprint. I see no evidence of any floor assemblies whatsoever. None. Zero. Nada.

Unless and until that occurs, the Bazant Greening paper is a fantasy.

Evidence please.

[3bodyproblem]

Yes, I posted an answer a few posts above but you seemed to not notice. Is the term, "eyes wide shut" appropiate?

Lozenge seems to think that by "more of a standard collapse" after the lower block hits means is somehow the same as the original FEMA idea. Which is of course the idea that the initiating collapse is caused by a floor slab slipping it's bolts. He didn't bother reading well enough to figure out that I was in fact talking about an even long after the initial collapse. This is a trait common to most truthers: take words out of context, if that's not possible, ignore.

Too true, this seems to be the case with the NIST faq and the pancaking. Seems to me this has to do with initiation and not the global collapse. Mention pancaking and they say "Nope NIST says no so you are lying" It's frustrating, you need to be very particular in how you word things or they get confused, and they do it deliberately. TS1234 seems to do this a lot if I am to believe the discussions elsewhere in this forum. I vaguely remember TS posting this pic and getting answered, he just didn't like the answer.
TS I think you have been warned about this? I personally don't care, but I would be careful using this tactic. I'd rather see you corrected by 50 people than banned :)

[TruthSeeker1234]

I certainly don't recall anyone posting evidence for mass inside the footprints. What is the evidence?

[3bodyproblem]

This theory allows for (at most) about 20% of the mass of the towers to be ejected outside the footprint. This means that 80% or more would have to remain inside the footprint.

There is no evidence for this at all. I have requested at least a dozen times, and I will repeat the request now.

Please link us to any evidence whatsoever that 80% or more of the mass of each tower remained in the footprint. I see no evidence of any floor assemblies whatsoever. None. Zero. Nada.

This is known as the CT CD/PC paradox. It was a controlled demo because it fell in its footprint but it wasn't a progressive collase because it didn't fall in its footprint. :)

[lozenge124]

Lozenge seems to think that by "more of a standard collapse" after the lower block hits means is somehow the same as the original FEMA idea. Which is of course the idea that the initiating collapse is caused by a floor slab slipping it's bolts. He didn't bother reading well enough to figure out that I was in fact talking about an even long after the initial collapse. This is a trait common to most truthers: take words out of context, if that's not possible, ignore.

Perhaps you should read the NIST faq and Bazant et al more closely.

NIST’s findings do not support the “pancake theory” of collapse, which is premised on a progressive failure of the floor systems in the WTC towers.

In the structural engineering community, one early speculation was that, because of a supposedly insufficient strength of the connections between the floor trusses and the columns, the floors ‘pancaked’ first, leaving an empty framed tube, which later lost stability. This hypothesis, however, was invalidated at NIST (...).

The "pancake theory" is one that refers to the entire building collapse not just the initiating moments as you seem to be implying. The idea that the collapse progressed because "force easily overcomes the connections of the floors to the columns" is obsolete and not supported by NIST whether at initiation or at any point thereafter (unless you disagree with NIST of course).

[3bodyproblem]

I certainly don't recall anyone posting evidence for mass inside the footprints. What is the evidence?

Lol, we were talking about the picture, not the mass in the foot prints.

TS could you please try and incorporate what you think happened when you ask questions? I'd hate to spend 10 minutes explaining something to you, only for you to say "But it was dustified by a space beam..." :)

I think you have been directed to Bazant's work on how they arrived at the 80% figure.

[Newtons Bit]

Perhaps you should read the NIST faq and Bazant et al more closely.

The "pancake theory" is one that refers to the entire building collapse not just the initiating moments as you seem to be implying. The idea that the collapse progressed because "force easily overcomes the connections of the floors to the columns" is obsolete and not supported by NIST whether at initiation or at any point thereafter (unless you disagree with NIST of course).

I never said "the pancake theory". I said pancake collapse. I am not responsible for you changing my words. If you do not understand what I write, I will not apologize to you. If you actually read what I said in CONTEXT, you would realize what I was saying had NOTHING to do with the FEMA pancake theory. Especially if you had taken the time to look through the calculations I've done regarding what the energy requirements for failing one floor/column would be.

[3bodyproblem]

Lozenge: No one said the floors pancaked and left an "empty framed tube" here. This is why you are mistaken.

[lozenge124]

Too true, this seems to be the case with the NIST faq and the pancaking. Seems to me this has to do with initiation and not the global collapse. Mention pancaking and they say "Nope NIST says no so you are lying" It's frustrating, you need to be very particular in how you word things or they get confused, and they do it deliberately. TS1234 seems to do this a lot if I am to believe the discussions elsewhere in this forum. I vaguely remember TS posting this pic and getting answered, he just didn't like the answer.
TS I think you have been warned about this? I personally don't care, but I would be careful using this tactic. I'd rather see you corrected by 50 people than banned :)

NIST made this kind of confusion inevitable by deciding not to cover the collapse beyond initiation in any detail in their report. Whatever side of the fence you are setting, clearly they did not satisfy their mandate to explain "how and why WTC1 and WTC2 collapsed" (NISTNCSTAR1 p.xxix).

[TruthSeeker1234]

This is known as the CT CD/PC paradox. It was a controlled demo because it fell in its footprint but it wasn't a progressive collase because it didn't fall in its footprint. :)

It was WTC7 that imploded into its footprint. The twin towers exploded. Almost none of the towers' mass ended up in the footprints.

[lozenge124]

I never said "the pancake theory". I said pancake collapse. I am not responsible for you changing my words. If you do not understand what I write, I will not apologize to you. If you actually read what I said in CONTEXT, you would realize what I was saying had NOTHING to do with the FEMA pancake theory. Especially if you had taken the time to look through the calculations I've done regarding what the energy requirements for failing one floor/column would be.

For the record, I was quoting from the NIST faq:
NIST’s findings do not support the “pancake theory” of collapse, which is premised on a progressive failure of the floor systems in the WTC towers.

[Newtons Bit]

NIST made this kind of confusion inevitable by deciding not to cover the collapse beyond initiation in any detail in their report. Whatever side of the fence you are setting, clearly they did not satisfy their mandate to explain "how and why WTC1 and WTC2 collapsed" (NISTNCSTAR1 p.xxix).

Uhh, no, they did. You see, to any engineer, all the information about how and why the collapse happened is why the building originally failed. It is the msiguided laypeople who yell "we want the truth!" who seem to think that what happened after the initial collapse has any bearing on building safety or responsibility of the engineer/owner/contractor.

There is no reason to investigate what happened after the initial collapse started. Studying the collapse prior to that can yield information that will further our undertanding of structural mechanics which can then be used to modify building codes. Which by the way, the study has already done. Most codes have already introduced new provisions based upon the NIST study.

Studying the collapse after it happened is a waste of money and would serve almost no purpose to furthering understanding of structural mechanics. The only thing it would do is appease the ignorant and bitter in the population for a few minutes before one in their ranks steps forward and says, "omg lol this is wrong!!21" and then we're right back where we started except that there's less money to fund actual real research that could save lives.

[Newtons Bit]

For the record, I am quoting the NIST faq:
[/B]

For the record, I never said "The Pancake Theory". So why the [rule8] are you quoting it?

[Jonnyclueless]

I'm not tew smurt with this kinda stuff, but momma always said that gravity pulls things down, not sideways. If the building below the tip is not longer underneath the top, why would the top fall to the side?

If I jump off a building, i don't continue to fall at my angle of jump. I quickly go straight down. If someone pushes me I fall over to the side. Because the ground is a pivotal point. If someone pushed me, then dropped the ground out from underneath me, I wouldn't fall sideways, I would start to go straight down once the ground was gone. And I would probably be tiled at the same degree I was just as the ground was removed.

And Momma says Alligators are ornery because they got all them teeth.

[Corsair 115]

The twin towers exploded. Almost none of the towers' mass ended up in the footprints.No, they collapsed, and debris was spread quite widely due to the chaotic way it collapsed. Where is the problem?

[3bodyproblem]

NIST made this kind of confusion inevitable by deciding not to cover the collapse beyond initiation in any detail in their report. Whatever side of the fence you are setting, clearly they did not satisfy their mandate to explain "how and why WTC1 and WTC2 collapsed" (NISTNCSTAR1 p.xxix).

I think you are misinterpreting the mandate. But I wish they would have had the time and money to explain the global collapse as well.

Of course had they done this I think I would just be in another forum debating with you about recreating the sinking of the Titanic.

[TruthSeeker1234]

Lol, we were talking about the picture, not the mass in the foot prints.

TS could you please try and incorporate what you think happened when you ask questions? I'd hate to spend 10 minutes explaining something to you, only for you to say "But it was dustified by a space beam..." :)

I think you have been directed to Bazant's work on how they arrived at the 80% figure.

I know how Greening and Bazant arrived at the 80% figure. If any more than 20% of the mass went outside the footprint, then there is no longer enough accumulating mass to sustain the "collapse". The problem is, sir, there is no evidence to support the position.

They calculate the force of the accelerating mass at each story. They notice that for collapse to continue, at least 80% of the mass above the collapse front must accumulate, and contribute to the force applied to the subsequent story. If any more than 20% goes over the side, the "collapse" will halt. So they "conclude" that >80% must have stayed inside.


Greening/Bazant is thus circular reasoning. Assume collapse. For collapse to continue, >80% must stay inside. The collapse continued. Therefore, >80% stayed inside.

That is how they "arrived" at the figure. Only by assuming a "collapse" can one "arrive" at that figure.

Circular reasoning is not evidence.

Scientists require evidence.

[lozenge124]

Lozenge: No one said the floors pancaked and left an "empty framed tube" here. This is why you are mistaken.

I am not saying this, Bazant/Le/Greening/Benson are:
In the structural engineering community, one early speculation was that, because of a supposedly insufficient strength of the connections between the floor trusses and the columns, the floors ‘pancaked’ first, leaving an empty framed tube, which later lost stability.

But I believe they are referring to the 2002 FEMA "World Trade Center Building Performance Study" popularized in the NOVA PBS program.

[pomeroo]

I think you are misinterpreting the mandate. But I wish they would have had the time and money to explain the global collapse as well.

Of course had they done this I think I would just be in another forum debating with you about recreating the sinking of the Titanic.



I often wonder how the loons would have reacted if the Impossibly Vast Conspiracy really did fly planes into the Twin Towers and claimed that the ensuing collapses were the result of explosives planted by Arab terrorists.

Let's see: you'd have the gubmint arguing that the planes had nothing to do with the buildings falling down, and the other side would be demanding to see proof that explosives had been planted.

I also wonder how, if the evildoers argued that there were no planes, that all those witnesses were deluded, our imaginative friend Ace would have demonstrated the reality of the planes.

Makes you kinda dizzy.

[lozenge124]

For the record, I never said "The Pancake Theory". So why the [rule8] are you quoting it?

Please enlighten us all to the differences between "pancake collapse" and "'pancake theory' of collapse". One is an event, the other is a theory? Splitting hairs a little?

[3bodyproblem]

No, they collapsed, and debris was spread quite widely due to the chaotic way it collapsed. Where is the problem?

There is some debate as to how much was in the footprint and how much was out of the footprint and why what was in was in and what was out was out. Oh, and how much that was in the footprint contributed to the collapse, how much that was out of the footprint didn't contribute and how much was in the footprint didn't contribute to the collapse. Oh, and how much was dust and how much was thermite and how much was spherules. And how much was melted and how much was molten. There's probably more, but these are the major ones.

:yikes:

[lozenge124]

I think you are misinterpreting the mandate. But I wish they would have had the time and money to explain the global collapse as well.

Of course had they done this I think I would just be in another forum debating with you about recreating the sinking of the Titanic.

Again, I am quoting directly from the Preface to NISTNCSTAR1:

The specific objectives were:

1. Determine why and how WTC 1 and WTC 2 collapsed following the initial impacts of the aircraft and why and how WTC 7 collapsed;
(...)

I think it's clear enough.

If someone were to produce a WTC style total "progressive" collapse in an FEA model, or even as a scale model, that would go a long way towards changing my mind about the plausibility of a gravity driven only collapse. "Global collapse ensues" just doesn't do it for me, sorry.

[Dave Rogers]

There is some debate as to how much was in the footprint and how much was out of the footprint and why what was in was in and what was out was out. Oh, and how much that was in the footprint contributed to the collapse, how much that was out of the footprint didn't contribute and how much was in the footprint didn't contribute to the collapse. Oh, and how much was dust and how much was thermite and how much was spherules. And how much was melted and how much was molten. There's probably more, but these are the major ones.

Or, to summarise, "We don't know how much fell in the footprint, or how much should have fallen in the footprint, but it definitely wasn't the right amount."

Dave

[3bodyproblem]

I know how Greening and Bazant arrived at the 80% figure. If any more than 20% of the mass went outside the footprint, then there is no longer enough accumulating mass to sustain the "collapse". The problem is, sir, there is no evidence to support the position.

They calculate the force of the accelerating mass at each story. They notice that for collapse to continue, at least 80% of the mass above the collapse front must accumulate, and contribute to the force applied to the subsequent story. If any more than 20% goes over the side, the "collapse" will halt. So they "conclude" that >80% must have stayed inside.


Greening/Bazant is thus circular reasoning. Assume collapse. For collapse to continue, >80% must stay inside. The collapse continued. Therefore, >80% stayed inside.

That is how they "arrived" at the figure. Only by assuming a "collapse" can one "arrive" at that figure.

Circular reasoning is not evidence.

Scientists require evidence.

Ugh, TS you butchered that one badly. You hardly need 80% of the mass to sustain the collapse.

I've got a cup of coffee and some free time. You give me an estimate of how much you think stayed in the footprint, I'll give you my counter offer, and we will see if we can arrive at a reasonable estimate of how much was in and how much was out. Then I will post it over at PhysOrg and see what happens. I don't like the 80% either, but I'm not sure what the exact number is.

[Dave Rogers]

If someone were to produce a WTC style total "progressive" collapse in an FEA model, or even as a scale model, that would go a long way towards changing my mind about the plausibility of a gravity driven only collapse.

For at least the third time, forget the scale model. All the properties scale differently with size, so a scale model will behave nothing like the full size building, and if the experimenters change the proportions of the model so it does behave like the full size building then you won't believe the results because they may have changed them so as to weaken the model too much.

Dave

[lozenge124]

For at least the third time, forget the scale model. All the properties scale differently with size, so a scale model will behave nothing like the full size building, and if the experimenters change the proportions of the model so it does behave like the full size building then you won't believe the results because they may have changed them so as to weaken the model too much.

Dave

Agreed, an FEA model would be better.
But a scale model of something, anything, undergoing a total progressive collapse would be a start - to show that it's possible at least. (and preferably without gimmicks like angle cut connections between the support columns and the like)

[Corsair 115]

But a scale model of something, anything, undergoing a total progressive collapse would be a start - to show that it's possible at least.Wait, let's back up a step. Are you saying you think a progressive collapse of a building is not possible at all except when explosives or something similar are used to weaken the structure?

[3bodyproblem]

I am not saying this, Bazant/Le/Greening/Benson are:
.

Just to clarify, there is a huge difference in pancake theory and pancaking. The NIST pancake theory was the one that left a hollowed out tube, which then collapsed. That's way different than if the floors fell on top of one another during the collapse. You either get this or you don't.
If I had a telestrator I could clarify it for you even better. If you want to make a fortune on the internet, make an online, real time telestrator that would work in the forums. Rich I tell yah, rich!!!

[lozenge124]

Wait, let's back up a step. Are you saying you think a progressive collapse of a building is not possible at all except when explosives or something similar are used to weaken the structure?

I am careful to say "total progressive collapse" and not simply "progressive collapse" meaning I am looking for a building that collapses totally - not a Ronan Point Apartment style partial collapse:
http://www.eng.uab.edu/cee/faculty/ndelatte/case_studies_project/Ronan%20Point_files/image002.jpg

Do you have any examples of such a total progressive collapse?

To answer your question, I have trouble seeing how a structure with vertical support columns can fail "floor by floor" because the vertical impact force of a falling "upper block" will be absorbed by the columns as a whole - not on a "floor by floor", progressive basis. But any examples would be appreciated.

[DavidJames]

II have trouble seeing how a structure with vertical support columns can fail "floor by floor" because the vertical impact force of a falling "upper block" will be absorbed by the columns as a whole - not on a "floor by floor", progressive basis. Have you read the NIST report, it provides the science behind what you "have trouble seeing"

[3bodyproblem]

Wait, let's back up a step. Are you saying you think a progressive collapse of a building is not possible at all except when explosives or something similar are used to weaken the structure?

The funny thing is building codes around the World already consider progressive or cascade collapses and how to prevent them. I'm pretty sure this is why NIST says, "...and then global collpase ensues" It's just understood by those who deal in a world where this "phenomenom" is very real.

[lozenge124]

Just to clarify, there is a huge difference in pancake theory and pancaking. The NIST pancake theory was the one that left a hollowed out tube, which then collapsed. That's way different than if the floors fell on top of one another during the collapse. You either get this or you don't.
If I had a telestrator I could clarify it for you even better. If you want to make a fortune on the internet, make an online, real time telestrator that would work in the forums. Rich I tell yah, rich!!!

I think you mean FEMA instead of NIST there.

But when the term "pancake" is invoked, to me it implies the failure of the truss connectors to the support columns, which causes each floor to fail in turn.

In the "pile driver" or crush down theory with the upper block crushing the lower block, floors from the upper block are hitting floors in the lower block certainly. But the main impetus in the collapse is the buckling and failing of the vertical core and perimeter support columns as they are hit from above by the upper block. So I don't think the term pancake is appropriate here - especially not if we are to distinguish it from the original theory.

[lozenge124]

Have you read the NIST report, it provides the science behind what you "have trouble seeing"

Yes I have.
And no it doesn't.

[3bodyproblem]

Do you have any examples of such a total progressive collapse?

To answer your question, I have trouble seeing how a structure with vertical support columns can fail "floor by floor" because the vertical impact force of a falling "upper block" will be absorbed by the columns as a whole - not on a "floor by floor", progressive basis. But any examples would be appreciated.

Dang, no I don't. I know it has happened, here in Vancouver I believe. I just don't have "proof". I will tell you it is a very real concern during construction, and I believe the case to which I am referring happened at just this time.

It would in the static case, but not in the dynamic case lozenge. Once the upper section started moving you need to consider how the energy is being transmitted componentwise.

[Newtons Bit]

Please enlighten us all to the differences between "pancake collapse" and "'pancake theory' of collapse". One is an event, the other is a theory? Splitting hairs a little?

Well, let's see. The Pancake Theory, as described by Fema, is a description of how collapse STARTED. Particularly, that the thermal expansion of the floors caused them to disconnect from their connections.

Pancake collapse, in context with what I said, is a collapse driven by a large upper block pancaking the lower block one floor at a time. This couldn't be more simple. "Pancake Theory" is how the collapse initiated. I was talking about something a great deal of time AFTER collapse initiated. But you didn't get that, you just honed right into the word "pancake", not realizing it just might have a meaning not directly associated with the "pancake theory". Do you really think the word pancake, as relating to structural terms, was never used before 2001?

[Newtons Bit]

To answer your question, I have trouble seeing how a structure with vertical support columns can fail "floor by floor" because the vertical impact force of a falling "upper block" will be absorbed by the columns as a whole - not on a "floor by floor", progressive basis. But any examples would be appreciated.

Follow the link in my signature. I calculated the resistance of an entire floors worth of columns. It's less than 10% of the total energy provided by a traditional upper block striking the lower block. The incidental resistance of the columns on the floors below can be calculated as well with the same procedure. The crux here is two things: one, what is the effect of vibration, it is significant, and the columns below can only be loaded to a certain degree before they too buckle.

[3bodyproblem]

Yah, I hate that term as well. As I have stated before, a pancake collapse is a term for what the collapse looks like AFTERWARDS. The floors remain intact and pile up like a stack of silver dollar pancakes at IHOP. This is common in smaller, concrete and steel reinforced buildings. For those of us familiar with this we know how to distinguish between a pancake collapse and pancake theory.

I'm looking at a "pile driver onto a small stack of pancakes collpase, that ultimately destroys the pancakes in the process" collapse. In this, it would seem that the small pile of pancakes may have surfed the wave just in front of the pile driver. Does this clarify things?

[lozenge124]

Well, let's see. The Pancake Theory, as described by Fema, is a description of how collapse STARTED. Particularly, that the thermal expansion of the floors caused them to disconnect from their connections.

Er, a floor's connections fail and the floor thus begins to fall - the collapse has initiated yet there has been no collision yet with the lower floor, so there has been no pancaking yet. "Pancaking" requires more than 1-floor, in this theory it refers to the failure mechanism AFTER initiation as the initial floor pancakes onto the next causing it to fail, and so on in cascade fashion. Pancaking is not a description of how the collapse started but how it progressed once started.

[lozenge124]

Follow the link in my signature. I calculated the resistance of an entire floors worth of columns. It's less than 10% of the total energy provided by a traditional upper block striking the lower block. The incidental resistance of the columns on the floors below can be calculated as well with the same procedure. The crux here is two things: one, what is the effect of vibration, it is significant, and the columns below can only be loaded to a certain degree before they too buckle.
I've seen your calculations and have also read Greening's "ENERGY TRANSFER IN THE WTC COLLAPSE". But they fail to convince me because they do not explain how the energy of the upper block impact is concentrated in the columns directly below the impact point without being transferred further on down. If you push down on a straw until it fails for example, it won't buckle directly below the top - in fact you cannot tell where it will buckle. Same if you drop a massive weight on a crane, you don't expect each "floor" or section to fail one after the other with no damage further down - the whole structure will absorb the impact as a whole because the support columns are in the same vertical axis as gravity.

I agree with Gordon Ross on this one:
Dr. Bazant argues that all of the potential energy associated with the fall of the upper section of the tower through two storey heights [the storey where the failure occurred and the uppermost storey in the lower section] would be concentrated into the destruction of the uppermost storey of the lower section. This energy would overwhelm the ability of the columns of the uppermost storey to absorb energy and collapse would progress through this storey. The available energy would then be concentrated into the next storey down and the tower would collapse one storey at a time to ground level.

The first error which Dr. Bazant has made is his assumption that all of the available energy would be utilised exclusively in the destruction of the uppermost storey of the lower section. This is physically impossible under any and all circumstances


Energy availability is a necessary condition for a crush down scenario, but not a sufficient one - the energy still has to be directed in the right directions to the right spots.

[3bodyproblem]

NO. A pancake collapse is a form of progressive collapse. I mean by definition that is. I don't mean to be difficult, but this is why people get confused. (and confuse me)

What if you consider the steel in the WTC was tapered, getting thicker as you go down. Does this change how you see the failure of the floors directly beneath the falling upper section? I imagine it like a pyramid getting crushed.

I don't agree with Gordo on that for one key reason. I think the lower section was more compromised by the falling debris than he assumes. This to me means the relative strengths of the upper and lower sections favour the upper section. At least for a period of time denoted by the freestanding core.

[lozenge124]

It would in the static case, but not in the dynamic case lozenge. Once the upper section started moving you need to consider how the energy is being transmitted componentwise.

I agree, but I think the only way to do that is through a FEA model and visualizations.
NIST didn't provide this, the Bazant & Greening style models simply assume that "energy is dissipated only at the crushing front" before developing their math; so what source do I go to to "consider how the energy is being transmitted componentwise"?

[3bodyproblem]

I agree, but I think the only way to do that is through a FEA model and visualizations.
NIST didn't provide this, the Bazant & Greening style models simply assume that "energy is dissipated only at the crushing front" before developing their math; so what source do I go to to "consider how the energy is being transmitted componentwise"?

NewtonsBit. :)

Since this was not an ideal collision (we have millions of small collisons happening at an angle) I'm visualizing everything crumbling in the core, while the exterior falls away after being detached from the truss connections. I say you end up with the upper section basically crushing the core, the floors taking care of themselves in a, dare i say pancake collapse, and the exterior basically falling away due to gravity. I think this also accounts for the speed of the collapse as well.

[Corsair 115]

Do you have any examples of such a total progressive collapse? I could counter that by asking if you have any other examples of major office towers which were struck by large passenger jetliners moving at a high rate of speed and carrying a large fuel load.

To answer your question, I have trouble seeing how a structure with vertical support columns can fail "floor by floor" because the vertical impact force of a falling "upper block" will be absorbed by the columns as a whole - not on a "floor by floor", progressive basis. But any examples would be appreciated.Given the sheer amount of mass which began moving in each WTC collapse, I cannot see how anyone would expect anything but a complete and total collapse.

[3bodyproblem]

I pushed this model of the collapse over at PhysOrg, but was shut down due to two things. I think this model ends up with more than 80% of the debris outside the footprint. This goes against what the big boys are saying. Who am I to argue this without making some serious calculations of my own ( I would have to work backwards from the conical pile of debris distribution from the FEMA report). More importantly, they say the inertial mass of the floors would slow the floor collapse (pancake) to such an extent that the upper section would "catch up" and ultimately become part of the crushing zone B. Until I get off my butt and prove otherwise I'm trumped on this.

[3bodyproblem]

Given the sheer amount of mass which began moving in each WTC collapse, I cannot see how anyone would expect anything but a complete and total collapse.

Yep, and Greening showed this rather conclusively IMO. The design of the building also meant that the support for the upper section was prettty much the core. If we extend that to the picture lozenge posted above, we see why it was "total" and not "partial".

Incidentally, I hate working on those suspended patios like we see in that picture, they make me nervous. And that picture didn't help either!

[Sword_Of_Truth]

The problem is, sir, there is no evidence to support the position.

Just a reminder; the person saying this claims that death rays from space vaporized the World Trade Center.

[lozenge124]

NewtonsBit. :)

Since this was not an ideal collision (we have millions of small collisons happening at an angle) I'm visualizing everything crumbling in the core, while the exterior falls away after being detached from the truss connections. I say you end up with the upper section basically crushing the core, the floors taking care of themselves in a, dare i say pancake collapse, and the exterior basically falling away due to gravity. I think this also accounts for the speed of the collapse as well.

Well that's great, but again, an FEA model is needed to see if your intuition is right. (I thought you boys were all about peer reviewed papers, not just personal opinions...)

On a side note, we had a debate at physorg about whether the perimeter floors would just "fall over" absent the floors, because this seems to be a common misconception of OCTers - that without the floors and core, the perimeter structure of the WTC would have just collapsed under it's own weight, as you appear to believe.

This section from the book "City in the Sky" makes clear that this was not the case at all, the outer walls.made of the perimeter columns held together by the spandrels was the main support structure of the WTC.
Like the horizontal lengths of wood that connect the staves, or vertical pieces, of a picket fence, deep steel plates called spandrels would run from one perimeter column to the next to give the building stiffness and let it resist the lateral force of the wind. Traditional buildings relied on the combined strength of their perimeter columns as well as everything inside them to resist the wind - from stiff masonry stair shafts, to the zigzagging steel cross-bracing and riveted connections of structural skeletons, to the great mass of the stone facades. There was a certain inefficiency here: using the relatively narrow interior of the building for stiffness was something like trying to resist a sideways push with feet spread. Much more efficient. In a building, less stell would be required for the same stiffness if the perimeter became the main element, rather than sharing the duty with the interior.

Such buildings would be akin to stiff tubes, filled with anything the owner wanted to put inside. Even after all the masonry and cross-bracing was stripped away, calculations at the Skilling firm showed, the structure would be stiffer than a traditional structure anyway, more than ten times stiffer. (p.120-121)

[Newtons Bit]

If you push down on a straw until it fails for example, it won't buckle directly below the top - in fact you cannot tell where it will buckle.

You don't understand how structures work. There is not 1 straw. There is 110 straws with 111 fingers. The straws vary from being large at the bottom to being smaller at the top. Each finger represents a floor, and this floor braces the straws against buckling. There is no buckling length over several floors. Each finger is a floor, it laterally braces the straw against buckling. The smallest straw will buckle first as it has the highest slenderness ratio. The force which causes the top-most straw to buckle is the same force the causes elastic strain energy in all the straws below. This buckling force is the peak force that the upper straw can transmit, and hence, this is the peak force that the straws below are subjected to. Ross has calculated the energy the lower columns absord (inaccurately I might add), and it is less than the energy required to completly fail the top most column.

It is rather obvious that the energy absorbed by the lower structure is small. In addition, and why I say that Ross calculates this inaccurately, is this impact causes a vibration through the lower structure. This vibration lowers the structural capacity of the lower members as the collapse continues. I can't quantify this number, but it's important to note that the way Ross calculated the energy of the lower structure is somewhat favorable to collapse prevention.

[Corsair 115]

This section from the book "City in the Sky" makes clear that this was not the case at all, the outer walls.made of the perimeter columns held together by the spandrels was the main support structure of the WTC.
(p.120-121)I note that the book excerpt you posted does not explicitly state the claim you made here:

On a side note, we had a debate at physorg about whether the perimeter floors would just "fall over" absent the floors, because this seems to be a common misconception of OCTers - that without the floors and core, the perimeter structure of the WTC would have just collapsed under it's own weight, as you appear to believe. It merely talks about the WTC structure being much stiffer than other buildings; it says nothing about the outer columns being able to stand on their own.

[lozenge124]

I could counter that by asking if you have any other examples of major office towers which were struck by large passenger jetliners moving at a high rate of speed and carrying a large fuel load.

Given the sheer amount of mass which began moving in each WTC collapse, I cannot see how anyone would expect anything but a complete and total collapse.

Here's a challenge: build a vertical structure such that when you impact it from above with a sledge hammer, it collapses "floor by floor" with no visible damage below the impacted "floor".

http://pharaqey.org/temp/PVC2.jpg

http://pharaqey.org/temp/PVC3.jpg

No angled cuts allowed in the structure, and no cheating with wedges or anything (the sledge hammer has to come down vertically).
Can you see why this is problematic?

Jim Hoffman has a more involved challenge too if you are interested:
http://911research.wtc7.net/wtc/analysis/challenge.html

[lozenge124]

I note that the book excerpt you posted does not explicitly state the claim you made here:

It merely talks about the WTC structure being much stiffer than other buildings; it says nothing about the outer columns being able to stand on their own.

So a stiff tube "filled with anything the owner wanted to put inside", "more than ten times stiffer" "than a traditional structure", would just fall apart with nothing inside?
Try reading again.
btw. are you saying you believe the perimeter columns would just peel off absent the floors then? :)

I can see how the WTC collapse is less problematic for those with these views, because all you have to do is collapse the floors by causing the truss connections to fail and the whole thing just comes down by itself.

[3bodyproblem]

Well that's great, but again, an FEA model is needed to see if your intuition is right. (I thought you boys were all about peer reviewed papers, not just personal opinions...)

On a side note, we had a debate at physorg about whether the perimeter floors would just "fall over" absent the floors, because this seems to be a common misconception of OCTers - that without the floors and core, the perimeter structure of the WTC would have just collapsed under it's own weight, as you appear to believe.

This section from the book "City in the Sky" makes clear that this was not the case at all, the outer walls.made of the perimeter columns held together by the spandrels was the main support structure of the WTC.
(p.120-121)

All I got is my opinion and I always try to make that perfectly clear. I'm lazy so I'm waiting for someone else to prove me right. Who wants to be the reviewee when it's so easy to be the reviewer. :)

I lurked for a bit while this discussion was going on over at PhysOrg. I missed the conclusion of it, so I am at a little of a disadvantage here. I think in the static state they were very strong, but they relied on the truss connection to do so. Once they were severed and in the dynamic all bets were off. While the spandrel cross bracing was important in the static, this would not be the case in the dynamic. Once you have lateral forces acting on the exterior you have a lot of weight acting on the connections between columns. Not to mention the top section was pushing it out of the way.

10 times stiffer than a traditional structure? Well yah, it had an exoskelton, most building just have what we call a "curtain". The WTC exterior was anything but a curtain that's for sure. However, stiffer does differ from strength. I like that, it's like "a pints a pound the world around" but for structural engineers.

[WildCat]

Here's a challenge: build a vertical structure such that when you impact it from above with a sledge hammer, it collapses "floor by floor" with no visible damage below the impacted "floor".

http://pharaqey.org/temp/PVC2.jpg

Oh dear Great Flying Spaghetti Monster...:eek:

[Newtons Bit]

Here's a challenge: build a vertical structure such that when you impact it from above with a sledge hammer, it collapses "floor by floor" with no visible damage below the impacted "floor".

http://pharaqey.org/temp/PVC2.jpg

http://pharaqey.org/temp/PVC3.jpg

No angled cuts allowed in the structure, and no cheating with wedges or anything (the sledge hammer has to come down vertically).
Can you see why this is problematic?

Jim Hoffman has a more involved challenge too if you are interested:
http://911research.wtc7.net/wtc/analysis/challenge.html

It's been done. I recommend you look at pictures of the collapse on 9/11. Snide comments aside, the problem with your picture, and why you have difficulty understanding this, is that your tower is is very slender. The WTC was not of similar proportions. Depth and Width are very important, as the floor slab laterally braces the one floor of columns. I can prove your "challenge" on paper, but hey, it's been done by people like Bazant. You may find problems in his last paper because they don't show crush up before crush down, but he still models an even that is almost exactly what you are looking for in your challenge.

[WildCat]

Here's a challenge:
Here's a challenge: Get a truther to publish a paper in a respected science journal. Will that ever happen? Do you ever wonder why it hasn't happened? Or never will happen? :rolleyes:

[3bodyproblem]

Here's a challenge: build a vertical structure such that when you impact it from above with a sledge hammer, it collapses "floor by floor" with no visible damage below the impacted "floor".

http://pharaqey.org/temp/PVC2.jpg

http://pharaqey.org/temp/PVC3.jpg

No angled cuts allowed in the structure, and no cheating with wedges or anything (the sledge hammer has to come down vertically).
Can you see why this is problematic?

Jim Hoffman has a more involved challenge too if you are interested:
http://911research.wtc7.net/wtc/analysis/challenge.html

Arrgh, lozenge you need to make that thing look tapered. From what I remember from the Greg Urich debate, the ratio was 16:1 over the length. Like this:


/\

[lozenge124]

You don't understand how structures work. There is not 1 straw. There is 110 straws with 111 fingers. The straws vary from being large at the bottom to being smaller at the top. Each finger represents a floor, and this floor braces the straws against buckling. There is no buckling length over several floors. Each finger is a floor, it laterally braces the straw against buckling. The smallest straw will buckle first as it has the highest slenderness ratio. The force which causes the top-most straw to buckle is the same force the causes elastic strain energy in all the straws below. This buckling force is the peak force that the upper straw can transmit, and hence, this is the peak force that the straws below are subjected to. Ross has calculated the energy the lower columns absord (inaccurately I might add), and it is less than the energy required to completly fail the top most column.

These are good points, but again I have trouble seeing how the upper "straw" can be subjected to a force that makes it buckle while the straw directly below it - subjected to the same transmitted force - has zero damage. We see massive perimeter sections being blown out at terrific speeds, while the structure below looks pristine. It's this damage "gradient" that to me is counterintuitive.

In any case my basic point is this: the NIST "global collapse ensues" hand waving, the few Bazant/Greening papers, your and Gordon Ross's submissions to the journal of 911 studies are not enough material to adequately cover the mechanics of the WTC progressive collapse. The assumptions and simplifications required to make the math manageable are too broad. We need an FEA model to validate the theory that the collapses could have happened under the force of gravity alone.

[3bodyproblem]

These are good points, but again I have trouble seeing how the upper "straw" can be subjected to a force that makes it buckle while the straw directly below it - subjected to the same transmitted force - has zero damage. We see massive perimeter sections being blown out at terrific speeds, while the structure below looks pristine. It's this damage "gradient" that to me is counterintuitive.

In any case my basic point is this: the NIST "global collapse ensues" hand waving, the few Bazant/Greening papers, your and Gordon Ross's submissions to the journal of 911 studies are not enough material to adequately cover the mechanics of the WTC progressive collapse. The assumptions and simplifications required to make the math manageable are too broad. We need an FEA model to validate the theory that the collapses could have happened under the force of gravity alone.


That's a fair enough request. While I think the money could be better spent, the US government has spent money on worse, less productive projects. Unfortunately, being in the minority, the onus would be on you to come up with the funds and resources to do so. I can only offer you my knowledge and insight at this time :)

[William Rea]

I'm not sure about he rest of the "JREF'ers", but I agree with the notion that a volume of the upper section underwent progressive collapse as the lower section underwent progressive collapse. "Crushed together" for the first few seconds of collapse. I'm not sure what you hope to prove with this? At some point the upper section did get crushed, to treat it before , after or during the colpase of the lower does little to change the validity of the math involved. It just changes the density of the crushing front. I believe Bazant admits this in the BandV paper if I remember correctly.
What do you think it means Rev91?

Don't have a problem with that except that "crushing into each other" does not imply "impulse deceleration". I'd just like to see the data for the impulse deceleration and how many of the upper block floors could have become detached?

[William Rea]

Before during or after collapse initiation? My understanding is the the floors pulled the exterior inwards at the point of impact, and only at initiation. After that neither were "bowing", although one section would have forced the other out of the way during impact. Either way, you can have the upper section getting tucked behind the lower during ythe collapse. I'm not a big fan of that analysis myself, but it is a valid consideration for the first few (2?) seconds of the collapse. It's certainly not an outrageous claim, I've heard worse. Those guys put more effort into the analysis than I have, so if push came to shove I would yield to them. I'm just not feeling it.

My undestanding is that the sagging trusses in the lower block pulled the outer columns inwards and this is backed up by visual evidence. I believe this was put forward to support the sagging trusses theory.

I am talking prior to the collapse.

Have you tried getting two end tapered tubes of similar diameter to slide into each other?

[William Rea]

Uhh, no, they did. You see, to any engineer, all the information about how and why the collapse happened is why the building originally failed. It is the msiguided laypeople who yell "we want the truth!" who seem to think that what happened after the initial collapse has any bearing on building safety or responsibility of the engineer/owner/contractor.

There is no reason to investigate what happened after the initial collapse started. Studying the collapse prior to that can yield information that will further our undertanding of structural mechanics which can then be used to modify building codes. Which by the way, the study has already done. Most codes have already introduced new provisions based upon the NIST study.

Studying the collapse after it happened is a waste of money and would serve almost no purpose to furthering understanding of structural mechanics. The only thing it would do is appease the ignorant and bitter in the population for a few minutes before one in their ranks steps forward and says, "omg lol this is wrong!!21" and then we're right back where we started except that there's less money to fund actual real research that could save lives.

You might be right that the initiation is all that requires investigation in economic terms but actually, as people aren't we interested in what happened? I find your comment that we're just not interested in such an incredibly important event very curious.

[Newtons Bit]

These are good points, but again I have trouble seeing how the upper "straw" can be subjected to a force that makes it buckle while the straw directly below it - subjected to the same transmitted force - has zero damage. We see massive perimeter sections being blown out at terrific speeds, while the structure below looks pristine. It's this damage "gradient" that to me is counterintuitive.

In any case my basic point is this: the NIST "global collapse ensues" hand waving, the few Bazant/Greening papers, your and Gordon Ross's submissions to the journal of 911 studies are not enough material to adequately cover the mechanics of the WTC progressive collapse. The assumptions and simplifications required to make the math manageable are too broad. We need an FEA model to validate the theory that the collapses could have happened under the force of gravity alone.

It has to do with elastic strain. The upper column buckles at a certain force, below the plastic limit. The column below it is slightly larger. It does not buckle and stays in the elastic stress range. That column unloads most of that energy (in a dynamic manner) when the columns above go into post buckling bending as there is less and less vertical force applied to the lower columns.

This is not over simplification.

[Alt+F4]

I'm assuming of course that she says this weapon is in low Earth orbit. This raises its own problems since in LEO an object will not be spending very long over the same part of the Earth's surface.

Excellent point. A satellite in low earth orbit takes about 90 minutes to orbit the earth, so how was Dr. Judy's flying microwave oven able to hit WTC1 at 8:46am and then WTC2 only 15 minutes later, at 9:02?

In regard to WTC2, how was the evil conspirators able to perfectly coordinate the space based attack with the TV fakery and the mass brainwashing of the eyewitnesses?

[Corsair 115]

Excellent point. A satellite in low earth orbit takes about 90 minutes to orbit the earth, so how was Dr. Judy's flying microwave oven able to hit WTC1 at 8:46am and then WTC2 only 15 minutes later, at 9:02?The counter would be to say the orbital weapon was in geostationary orbit, and thus stays over the same part of the Earth's surface all the time. The problem there is that geostationary orbit requires a much larger distance from the Earth; low Earth orbit is at an altitude between 124-1,240 miles but geostationary orbit is at an altitude of 22,300 miles. That's more some 18 times further away than the highest level of LEO. Being that much further away greatly complicates the aiming process as well as greatly increasing the power required by this supposed weapon.

[GlennB]

Excellent point. A satellite in low earth orbit takes about 90 minutes to orbit the earth, so how was Dr. Judy's flying microwave oven able to hit WTC1 at 8:46am and then WTC2 only 15 minutes later, at 9:02?
...


This is also a major hangup for that brand of moon hoax twoofers who maintain that the Apollo astronauts spent the entire mission in earth orbit, while maintaining "lunar direction", so as not to spook the tracking stations (although, given the angles involved, they would have been spooked anyway. But it's all b#llocks anyway, as we know).

It ain't physically possible to stay that low and go that slow.

[3bodyproblem]

My undestanding is that the sagging trusses in the lower block pulled the outer columns inwards and this is backed up by visual evidence. I believe this was put forward to support the sagging trusses theory.

I am talking prior to the collapse.

Have you tried getting two end tapered tubes of similar diameter to slide into each other?

Well like I said before, I'm not a big proponent of the "turtle" theory. In fact, two or three days before Jones released this paper to the public I made almost the same observations over at PhysOrg. By my observations most of the upper section, excluding possibly the truss hat, was commuted in the collapse, as is evident by the freestanding core. I fail to see how the solid upper section could have passed through the core undamaged at the point it becomes visible. There is some speculation that the tilt/deflection may have allowed this to occur. I feel however that the extent to which the tilt/deflection had to occur for this to happen is so great as to be unreasonable.

[einsteen]

It has to do with elastic strain. The upper column buckles at a certain force, below the plastic limit. The column below it is slightly larger. It does not buckle and stays in the elastic stress range. That column unloads most of that energy (in a dynamic manner) when the columns above go into post buckling bending as there is less and less vertical force applied to the lower columns.

This is not over simplification.

Wouldn't that imply an exponential strength ? That would certainly arrest the collapse.

[3bodyproblem]

Wouldn't that imply an exponential strength ? That would certainly arrest the collapse.


The steel thickness increased linearly, but the strength increased exponentially? I can see how that makes sense...
:boggled:

[einsteen]

For at least the third time, forget the scale model. All the properties scale differently with size, so a scale model will behave nothing like the full size building, and if the experimenters change the proportions of the model so it does behave like the full size building then you won't believe the results because they may have changed them so as to weaken the model too much.

Dave

Scale models are also used in wind tunnels, of course you are right that it is hard to scale the wtc, you should scale each floor's mass with the same factor, the energy values E1 with the same factor, gravity cannot be scaled, but the system is invariant as long as gh is constant, i.e. h the distance between the floors. You should place the model in a centrifuge. Furthermore you don't need a full building, a stepwise collapse of a few floors is enough proof for global collapse. Collapse initiation is no proof of global collapse, I have higher standards for a scientific proof.

[einsteen]

The steel thickness increased linearly, but the strength increased exponentially? I can see how that makes sense...
:boggled:

I was refering to the implications of Newton Bit's model, since you correctly understand that this could not be the case NB cannot explain the stepwise collapse (see Lozenge124's notes). Remember reaction force needed to crush a story. Folks the answer could be so extremely simple and it would explain everything.

[William Rea]

Well like I said before, I'm not a big proponent of the "turtle" theory. In fact, two or three days before Jones released this paper to the public I made almost the same observations over at PhysOrg. By my observations most of the upper section, excluding possibly the truss hat, was commuted in the collapse, as is evident by the freestanding core. I fail to see how the solid upper section could have passed through the core undamaged at the point it becomes visible. There is some speculation that the tilt/deflection may have allowed this to occur. I feel however that the extent to which the tilt/deflection had to occur for this to happen is so great as to be unreasonable.

Could you explain "turtle" theory for me please.

[3bodyproblem]

I was refering to the implications of Newton Bit's model, since you correctly understand that this could not be the case NB cannot explain the stepwise collapse (see Lozenge124's notes). Remember reaction force needed to crush a story. Folks the answer could be so extremely simple and it would explain everything.

I'm not sure how NB explains it, but I think it has a lot to do with the truss connections that failed prior to the application of this force. As hard as it may seem to believe, there is a good chance that the upper section did remain structurally sound for a period of time after initiation. At least relative to the lower section. If we are to believe the greening model, only a small amount of mass was needed to ensure progressive collapse (about 4 floors of mass). This accumulated mass, what's it called Zone B?, perhaps it did more of the damage to the lower part than you are assuming the upper part did?

[3bodyproblem]

Could you explain "turtle" theory for me please.

Lol, this idea that the upper section slipped in behind the lower section in the picture.

[William Rea]

Lol, this idea that the upper section slipped in behind the lower section in the picture.

OK, thanks for that. A whole language appears to be developing for this thing.

[Newtons Bit]

Wouldn't that imply an exponential strength ? That would certainly arrest the collapse.

How the heck did you come to that conclusion. Linear != exponential.

[einsteen]

Straw man

[jsfisher]

The counter would be to say the orbital weapon was in geostationary orbit, and thus stays over the same part of the Earth's surface all the time. The problem there is that geostationary orbit requires a much larger distance from the Earth; low Earth orbit is at an altitude between 124-1,240 miles but geostationary orbit is at an altitude of 22,300 miles. That's more some 18 times further away than the highest level of LEO. Being that much further away greatly complicates the aiming process as well as greatly increasing the power required by this supposed weapon.

Not only is the aiming more a problem from 22,300 miles, the weapon, itself, would need to be over the equator to be in a geostationary orbit. The energy beam fired from the weapon wouldn't be straight down on either tower. At best it would be 47 degrees from vertical.

[Newtons Bit]

Straw man

Are you going to explain yourself? Or just keep speaking gibberish and going "nyah nyah nyah" with your fingers in your ears.

[einsteen]

Are you going to explain yourself? Or just keep speaking gibberish and going "nyah nyah nyah" with your fingers in your ears.

Don't you understand how big the difference between two stories should be if only the current story i is crushed and not i+1. OCT'ers always correctly mention the difference between static and dynamical forces, now what do we have now, say we are at 3/4 of the collapse and a complete building's mass collapses with 40 m/s on a floor and still only that story breaks. The collapse model says (by definition!) it doesn't affect the one below that one in the slightest way. ;)

[Dave Rogers]

Scale models are also used in wind tunnels, of course you are right that it is hard to scale the wtc, you should scale each floor's mass with the same factor, the energy values E1 with the same factor, gravity cannot be scaled, but the system is invariant as long as gh is constant, i.e. h the distance between the floors. You should place the model in a centrifuge.

And then the truth movement replies, "They built a scale model of the towers, but they had to put it in a centrifuge to make it collapse! They cheated!! It doesn't prove the real towers would have collapsed!!! Gravity doesn't change!!11!!! PWN3D!!ELEVENTYONE!11!!"

Either you build a scale model, scaled in linear dimensions only, and it doesn't collapse, so the truth movement claims the test proves the real towers wouldn't have collapsed, or you build a model with adjustments so that the scaling of material properties, forces and energies is correct, in which case the truth movement claims the model was adjusted so as to ensure collapse. And so it will never, ever be possible using scale models to advance any evidence for global collapse that the truth movement will accept. As for the serious structural engineering community, they already accept that global collapse is a reasonable outcome anyway. So any attempt at analysis using scale models, from the point of view of the 911 truth debate, is completely pointless.

Dave

[einsteen]

Good point of course Dave.

[Belz...]

My thread was on Greening's paper. In it, he said there was a top block which remained intact until it "crushed down" through the lower building, all the way to the ground. Then (and only then), the top block itself underwent "Crush Up".

Greening has been forced to abandon this idea. How any honest person could have ever entertained it is beyond me, precisely because of observations such as are made in the graphic posted by Rev.

Indeed. Same with concepts such as "dustification".

It was WTC7 that imploded into its footprint. The twin towers exploded.

I think the word you're looking for is "collapse".

Scientists require evidence.

And you're evidently not a scientist...

[Belz...]

Here's a challenge: build a vertical structure such that when you impact it from above with a sledge hammer, it collapses "floor by floor" with no visible damage below the impacted "floor".

Uh-huh. Build it full scale, and see what happens.

[Belz...]

Straw man

Gosh, you truthers love to say that.

[Newtons Bit]

Don't you understand how big the difference between two stories should be if only the current story i is crushed and not i+1. OCT'ers always correctly mention the difference between static and dynamical forces, now what do we have now, say we are at 3/4 of the collapse and a complete building's mass collapses with 40 m/s on a floor and still only that story breaks. The collapse model says (by definition!) it doesn't affect the one below that one in the slightest way. ;)

Sorry bud, if one column has a compressive strength of 1200 kips and the one below 1205 kips, the one below will not buckle and the one above will. The point in which a column is the peak axial force it can resist and transmit. The column below CANNOT buckle if there is not a high enough load applied to it. If a column does not buckle, it remains in the elastic stress-strain region. It does not permanently deform. This is BASIC mechanics.

(i+1)/i could be as small as 1.01 and it would, theoritically, be the same.

[einsteen]

I re-readed NB's post and he is probably correct that an increasing strength could be play a role in the stepwise collapse. And I made the mistake that the energy and momentum of the collapsing mass has nothing to do with the force itself, apologies. (I came to the exponential thought because of this, but math should be worked out precisely first) But then if you use a linear behaviour and also assume that the E1 values are also lineair then you of course have a simple linear function. Some input then is needed to calibrate the function. The linearity is also consistent with the normal static forces that the building should handle, assuming the floors have equal mass. To be continued.

ps. You posted while I was typing... :-)

[einsteen]

I'm still wondering if you do this experiment for Spaghetti with a linear increasing strength

http://www.math.psu.edu/belmonte/sg9.gif

[Newtons Bit]

I'm still wondering if you do this experiment for Spaghetti with a linear increasing strength

http://www.math.psu.edu/belmonte/sg9.gif

It cannot be one long skinny tapering rod. It needs to be non-slender columns supported by a floor diaphragm. Each column in a column line the buckles individually.

[einsteen]

Newtons, There is something to add to the story. Even if you have a theoretical 1d model in which each story's force increases lineair to the bottom, we are still talking about a coupled system. The maximal force reached is not something that is part of the dropping block, that depends on the whole reaction of the building, a story only reaches its maximal force if you compress it, but before it reaches its maximal force the artificial theoretical model will also be compressed at lower levels and the maximal force is not reached. I think the situation is too complex and could only be solved with coupled differential equations. You can set them up, but what then...:(

[lozenge124]

Sorry bud, if one column has a compressive strength of 1200 kips and the one below 1205 kips, the one below will not buckle and the one above will. The point in which a column is the peak axial force it can resist and transmit. The column below CANNOT buckle if there is not a high enough load applied to it. If a column does not buckle, it remains in the elastic stress-strain region. It does not permanently deform. This is BASIC mechanics.


Well, it's not as clear cut because the lower column has to carry the upper one so it depends how heavy the top column is - this is added stress on the lower one. Additionally, the WTC columns were also carrying the weight of the floors and in the chaos of the collapse, with the upper block tilting over, the very upper floors (connected to the upper column sections) could have been damaged/compromised resulting in LESS compression on the upper sections than the sections below still carrying their full floor load. This could result in lower columns buckling before the upper ones.
So, it doesn't seem to me to be that simple, especially when you consider the spandrels tying the columns together in larger units etc.

Also, in looking at pictures of the collapse and the debris afterwards, it seems that many (most?) of the perimeter columns were relatively straight and failed at the bolt connections.
http://www.jonesreport.com/images/090806WTC1.jpg http://www.melbourne.indymedia.org/uploads/1344.jpg

Does this jive with your concept of the uppermost columns buckling? It seems to me not - to explain this I think you have to consider at least 2 columns "buckling" as a unit in a v-shape until the bolts are torn off.

We also know that a huge chunk of the North tower was ejected with tremendous horizontal velocity enabling it to travel 390ft and embed itself partially in the WFC building:
http://pharaqey.org/temp/WFCblock.jpg
http://youtube.com/watch?v=wW55hdXUJvk)

Can this kind of event be explained in terms of vertical, gravitational forces alone without invoking horizontal explosive bursts? Maybe, but IMHO it requires more work than what has been seen up to now.

[Belz...]

http://forums.randi.org/imagehosting/thum_608045892c4f64e35.jpg (http://forums.randi.org/vbimghost.php?do=displayimg&imgid=3266)

http://forums.randi.org/imagehosting/thum_608045892c65f25a4.jpg (http://forums.randi.org/vbimghost.php?do=displayimg&imgid=3267)