The 9/11 Forum

OneWhiteEye wrote:On the subject of item 1 in the OP:

(1) Assertion: when a building collapses, in order to do crushing work, it must decelerate because of structural resistance, according to Newton's 2nd and 3rd law of motion.

It can accelerate, so I would rephrase this to remove the word 'decelerate'. Perhaps:

when a building collapses, in order to do crushing work, there must be a associated force due to structural resistance such that the net acceleration of the building center of mass must be less than freefall...

Hm. A little cumbersome perhaps.

Right, it can accelerate if the resistance is less than that required to support the static load.

I didn't mention acceleration because that all depends on how you average out, right?

When I say decelerate I meant the very short period of time where load is amplified. What Tony discussed in the other thread

In that sense the definition is correct? Or still incomplete? Thanks for scrutinizing the premises, that's what I hoped for!

Perhaps...

(1) Assertion: when a building collapses, in order to initially overcome the resistance of the lower structure through load amplification, the upper block must decelerate and cannot sustain full freefall, according to Newton's 2nd and 3rd law of motion

?

Only if the upper block is a homogeneous structure and acts as a block with all the components and their connections neither deforming or fracturing in the collapse.

OneWhiteEye wrote:
Assertion: when a building collapses, in order to do crushing work, it must decelerate because of structural resistance, according to Newton's 2nd and 3rd law of motion.

Bazant discusses this misapplication of newton, by truthers, in one of his papers. The OP does it to, for s/he has no idea how to apply it.

Because I asked you a question which interested me, not one which pandered to your imagination.

No. Because it's a very simple and very probable explanation that explains the free fall, and is at the very least, backed by some photo evidence that this was in fact the case.

This of course destroys truther claims of cd. This is why there so far has been little honest discussion of it.

Your claim, supported by a single photograph showing a very small percentage of column ends out of the total,

You should note that this was the first photo, on the first website that I checked, that looked like it held any promise. And it does, at the very least, prove that this happened for at least some of them.

is that fracture is responsible for negligible resistance over the interval in question. I do not disagree with that premise, though you've hardly proven anything of the sort with your statistically insignificant sample.

My purpose for questioning all here about this is to not try and prove anything, but rather to stir some honest discussion on the subject, since I noticed it was NOT being discussed yet, from what I could see. If you HAVE covered this subject, then I apologize.

Tony pointed out the buckling conformations associated with the NIST physics simulation are consonant with a descent at substantially less than freefall, an attribute also displayed by the sim, thus showing self-consistency and adherence to basic physical principles

Yes, I've read that. I'm also not aware of the limitations of the sim either. I don't know if it's possible to model the connection weaknesses, nor if they were done. From memory, the sim doesn't show much of the descent at all though, so I don't know if this even applies to the free fall time period. Educate me on this.

Also from memory, they show core columns fracturing during the interior collapse, but don't remember ext columns fracturing, although this 'might' be cuz of it not extending to this time.

Feel free to throw NIST's sim under the bus

Why would anyone do that? NIST acknowledges the computational difficulties with them (there were 4) and their purpose. Which was to find out if there would be differences in the various collapse mechanisms. And there were. Most interesting was the realization that removal of a section of column 79, with zero impact or fire damage, would result in a progressive collapse. They thus described an unexpected design flaw in 7.

but at least recognize you're trodding on unsubstantiated ground with this fracture thing. Like I say, I may even agree with you, but I wouldn't proclaim it unless I had some pretty solid proof. This I have not seen.

I'm not trying to prove anything, as I said.

I've rather easily provided photo evidence that there is a reason to investigate this further.

I have zero interest in trying to change anyone's mind here, but would enjoy seeing where the discussion went. That's all.

So then you're not going to state your case as to why load transfers can't happen in "less than a second"?

Ok then.

You haven't made your case. therefore, there's zero reason to give your bare assertion any effort in discussing it.

Joey Canoli wrote:Bazant discusses this misapplication of newton, by truthers, in one of his papers. The OP does it to, for s/he has no idea how to apply it.

You know what I bet? I bet you don't know how to apply it. I'll bet you don't even know in which paper Bazant carries through the equations of motions to show Newton's laws are applied correctly. If you wish to show otherwise, start with citing the paper in which the analysis is made explicit. That shouldn't be too hard, that tidbit is littered all over this forum, there's even a huge thread devoted to precisely this analysis.

I'm confident you don't know what you're talking about because even Bazant makes clear and explicit that there is a resistive force involved in buckling; he calculates this based on engineering estimate and it is quite substantial. This effective resistive force is applied to the upper block and retards its motion from freefall accordingly. This is what item 1 of the OP states.

No. Because it's a very simple and very probable explanation that explains the free fall, and is at the very least, backed by some photo evidence that this was in fact the case.

Simple? No. It was billed at the time as the most complex simulation of its kind, and I'm not aware of any subsequent work which grabs the title away.

Probable? This is somewhat subjective. I would readily accept possible, maybe accept plausible, but not probable. Yes, probable is what NIST says. You mean you accept this as the probable explanation and not just an expensive cartoon?

Backed by photo evidence? None of which I'm aware. If anything, the photo evidence strongly suggests NIST failed to capture the actual collapse mechanism, as the only large scale conformation observed was the kink. As Tony has said, their sim shows a retarded descent consistent with large scale conformations. Inconsistent with the image record, which shows near freefall of some portions and rapid global descent over the same interval.

Of course, fracture might explain it. But you've offered NIST's explanation as the probable cause, so have forfeited an argument until resolving the contradiction. NIST depicts very little fracture in their simulation. Their sim shows large-scale buckling. Bucking is a well-studied phenomena independent of fracture, another well-studied phenomena. The simulation you feel is the probable explanantion is entirely at odds with what you've just been saying, and you don't even know it.

You cannot simultaneously hold two mutually exclusive conditions to be true and use this as a platform of argumentation. Self-contradiction is worse than unsupported.

This of course destroys truther claims of cd. This is why there so far has been little honest discussion of it.

Sure, whatever. Do you understand you are arguing with a person who does not believe in CD? Pseduoscientific claptrap from the debunker side of the type you've recently been posting is the reasons there so far has been little honest discussion of alternate, more PROBABLE and non-CD failure modes of WTC7. I'm sure you didn't know that, either. Ill-formed arguments against CD do not advance the science of progressive collapse; at this forum, they are an impediment.

You should note that this was the first photo, on the first website that I checked, that looked like it held any promise.

Noted. Now, will you note that it is both a small sample and therefore inconclusive? Will you also acknowledge that fracture without significant buckling is contrary to the collapse mode depicted in the NIST sim?

And it does, at the very least, prove that this happened for at least some of them.

Yes, it does. I didn't say otherwise, and I've never argued against fracture as a dominant collapse mechanism even over the early period of interest. To the contrary, I'm on record here as arguing for it as a possible mechanism. The main differences are I've done so:

- utilizing good engineering principles
- carefully, mindful of the burden of proof
- painfully aware of the fact that I am at odds with NIST in proposing such an explanation

My purpose for questioning all here about this is to not try and prove anything, but rather to stir some honest discussion on the subject, since I noticed it was NOT being discussed yet, from what I could see. If you HAVE covered this subject, then I apologize.

Not as much as other things, but it has come up. Apology accepted, but please don't assume a lot about the people you're arguing with. Deal with the words served up at the moment. My "why not?" question that started our interaction stems from a great deal of hands-on research of the descent of WTC7, both observational and analytical. I feel a long ways from being able to confidently explain the collapse to my satisfaction. You may be satisfied with NIST's explanation; I am not. This is not the issue here, though, and was not the point of asking "why not?"

I asked the simple question because it leads to the whole can of worms that I suspected it would. You are flipping between two mutually exclusive arguments and are unaware of it. Both Tony and SnowCrash, whatever else they may be getting right or wrong in the grand scheme of things, were both attempting to deal with this conundrum without success. You stimulated honest discussion all right, but I'm afraid it is you that need to learn from the exchange in this particular instance.

OneWhiteEye wrote: Bazant makes clear and explicit that there is a resistive force involved in buckling; he calculates this based on engineering estimate and it is quite substantial.

Yep.

But he also makes it clear and explicit that he is ignoring column fracture, which he backs up as likely with both his expertise and a paper that backs it. He does this to give an upper bound case to resistance to eliminate all doubt that there is enough energy that even given the preposterous and unlikelihood of a direct axial column contact, that there would be no stopping the progressive collapse.

This doesn't help your case.

Probable? This is somewhat subjective.

Agreed.

I would readily accept possible, maybe accept plausible, but not probable.

Then you accept that it should be discussed honestly? Good.

Backed by photo evidence? None of which I'm aware.

Cute.

I said that there's 'some' photo evidence, and provided one photo of it. One is some. Do I seriously need to go to the trouble of looking at multiple photos? Not interested.

If anything, the photo evidence strongly suggests NIST failed to capture the actual collapse mechanism

If your statement is based solely on the animation, then you've first got to prove that it should have perfectly matched the recorded collapse. Otherwise, your just using a call to perfection fallacy.

As Tony has said, their sim shows a retarded descent consistent with large scale conformations. Inconsistent with the image record, which shows near freefall of some portions and rapid global descent over the same interval.

Which in no way answers my question about whether or not ext column fracture was in the sim parameters. Do you know?

Of course, fracture might explain it.

Yep.

But you've offered NIST's explanation as the probable cause

I have? I didn't know NIST offered column fracture as a reason for the rapid descent.

They haven't, right? I am merely adding my own thoughts to it.

so have forfeited an argument until resolving the contradiction.

Since there is none, I will continue.

The simulation you feel is the probable explanantion is entirely at odds with what you've just been saying, and you don't even know it.

Wrong.

You cannot simultaneously hold two mutually exclusive conditions to be true and use this as a platform of argumentation. Self-contradiction is worse than unsupported.

It is only contradictory to you, for you don't know the entirety of what I think.

Do you understand you are arguing with a person who does not believe in CD?

Always have.

Pseduoscientific claptrap from the debunker side of the type you've recently been posting is the reasons there so far has been little honest discussion of alternate, more PROBABLE and non-CD failure modes of WTC7.

I've seen very little discussion of column fracture here. This is the first discussion of it that I know of here.

You are proven wrong.

I'm sure you didn't know that, either. Ill-formed arguments against CD do not advance the science of progressive collapse; at this forum, they are an impediment.

What discussion of column fracture in 7 leading to the free fall period of the north face have I missed?

Now, will you note that it is both a small sample and therefore inconclusive?

Always did.

Will you also acknowledge that fracture without significant buckling is contrary to the collapse mode depicted in the NIST sim?

And yet, it's supported by observation of the tower columns, and would very likely be further supported in a photo examination of 7's debris.

painfully aware of the fact that I am at odds with NIST in proposing such an explanation

Only if the sim is able to reproduce ext column fracturing and connection strength. You don't know this, and it is unlikely anyone ever will, so it falls upon photo examination to make a decision to see if a conclusion can be made.

You may be satisfied with NIST's explanation

I am, if we limit it to the words. Some here seem to think that the sim should be a perfect reproduction of the collapse. How likely is that?

You stimulated honest discussion all right, but I'm afraid it is you that need to learn from the exchange in this particular instance.

I have.

I have learned quite a bit about some people here.

Joey Canoli wrote:Yes, I've read that. I'm also not aware of the limitations of the sim either. I don't know if it's possible to model the connection weaknesses, nor if they were done. From memory, the sim doesn't show much of the descent at all though, so I don't know if this even applies to the free fall time period. Educate me on this.

Now we're getting somewhere. I will return to this, here or another thread, as time permits.

Yes, it's theoretically possible to model the connections realistically, though maybe not practically so (at the time). I believe this is one of the aspects in which the sim falls short of reality. As is, you may be right about fracture, but both you and NIST cannot be correct.

Also from memory, they show core columns fracturing during the interior collapse, but don't remember ext columns fracturing, although this 'might' be cuz of it not extending to this time.

Yes, there is some interior connection failure. All I need to know is that buckling is depicted in the sim, the descent is depicted accordingly (slow) in the sim, and NIST specifically cites the "buckling region" when referencing the mode of collapse, not "fracture region". It is their explicitly declared collapse mechanism.

Why would anyone do that?

Well, as I explained above, you apparently. I guess you weren't savvy to the contradiction between your thesis (which is also my best guess) and the NIST model. I threw them under the bus within a day of their report coming out. This issue is not the only reason, but that discussion IS OT.

NIST acknowledges the computational difficulties with them (there were 4)...

I have no doubts about the computational difficulties of simulations of "unprecedented complexity". It is precisely for this reason that I will be automatically skeptical of any result which:

1) is not accompanied by a larger body of incremental subsystem FEA analysis, validated and calibrated by physical testing along the way
2) appears to contradict the image record

NIST's sim fails on both counts. They partially satisfy #1, but in my opinion not to a sufficient extent given the size and complexity of the model. A washing machine lid, yes, collapse of WTC7, no. It would be okay to let them slide on this if it weren't for #2, and this is where the rubber hits the road. No one can say with a straight face that any of the collapse sims match the kinematic observables, though somehow it happens all the time.

BTW, it used to be it never happened, until Daniel came along and solved the issue of deflection scaling, which was universally assumed by debunkers prior to this time. It still is to this day by the uninformed few who haven't reached that stage of cognitive dissonance yet in an attempt to preserve the sanctity of the NIST report. Go ahead, you don't have to be a truther to throw them under the bus, I did it. Feels good.

...and their purpose. Which was to find out if there would be differences in the various collapse mechanisms.

Indeed, that was one of their purposes, but you state it in the singular. I seem to remember something else, another purpose; I'll need to check the report again and see if I can find it. Ah, here it is, first paragraph of the abstract in NCSTAR 1A:

This report describes how the fires that followed impact of debris from the collapse of WTC 1 (the north tower) led to the collapse of WTC 7;

This is the second sentence of the report! We see their primary purpose is to explain the collapse of WTC7. As a natural consequence of standard practice parameter sensitivity analysis, variations in scenarios were explored. Their primary purpose does not even include mention of modeling the collapse itself, so it may be tempting to say NIST was pre-positioning the physics sim under the bus from the get-go, but I'm not letting them off that easy.

The reason they switched from the fire sim to the physics sim is because the fire sim cannot model collapse, it can only impose damage such that initial conditions for collapse are approached. From there, the physics sim takes over and must provide an explicit causative mechanism for collapse otherwise the collapse itself remains unexplained. Thus we see that the physics sim is the lynchpin of the NIST's proposed collapse explanation - it must be - which is stated as the primary purpose of the report in the second sentence.

Unfortunately, their collapse model contradicts one of my pet theories, rapid fracture skirting around the lower perimeter. If that's your theory, they contradict you, too. Pays to be aware of it. There's the bus...

It has become fashionable lately to claim that modeling the collapse itself was never a purpose of the report! That comparative damage simulation was the ONLY purpose. This is obviously false on casual inspection; the report states otherwise and, ultimately, of what value are comparative results between simulations that do not successfully model the underlying event?

Most interesting was the realization that removal of a section of column 79, with zero impact or fire damage, would result in a progressive collapse. They thus described an unexpected design flaw in 7.

Indeed they did. As I said, I've little choice but to be skeptical about the initial cause since the evolution from that point diverges rapidly. However, I do see the reasoning and it appears probable. Two things: I'm left wondering why all four sims diverge rapidly (have some ideas). Anyone who believes in HE CD now can say it's at least theoretically possible to take the whole bloody building down rather easily with small volumes, given sufficient planning. Sure, sure, the noise, I know; ears bleeding all over lower Manhattan.

I'm not trying to prove anything, as I said.

Speculation is fine. But I notice you are asking for proof in counterarguments, so be expected to be held to the same standard. You can always agree to disagree, or do the legwork to reinforce your position and hold firm. The one thing you cannot do is claim victory by simply ignoring facts and sound engineering mechanics principles, or by using a pair of contradicting claims to show the truth of one of them.

I've rather easily provided photo evidence that there is a reason to investigate this further.

Yep. Thanks. You've taken a small step towards an explanation of the collapse mechanics, all the same it's the right direction because it is incontrovertible observation as opposed to unprecedented simulation. As debunkers are fond of saying, nothing's stopping you from publishing your findings. It need not be perceived as refuting NIST, merely enhancing the description. But, if successful, you would supplant their model with a superior mechanism which is in fact incompatible with much of their stated position.

I have zero interest in trying to change anyone's mind here, but would enjoy seeing where the discussion went. That's all.

You succeeded in that regard. I don't expect you to change your mind, either, but would be pleased if you went past the first layer of the onion. Your instincts about the problem might be excellent. Better than NIST's.

Joey Canoli wrote:But he also makes it clear and explicit that he is ignoring column fracture, which he backs up as likely with both his expertise and a paper that backs it. He does this to give an upper bound case to resistance to eliminate all doubt that there is enough energy that even given the preposterous and unlikelihood of a direct axial column contact, that there would be no stopping the progressive collapse.

Yes, and I address that in the post from which you quote. You still haven't answered my question about why WTC1 is so slow when we know for a fact that fracture was a dominant mode of the collapse. If you simply ignore the question while persisting in arguing the domain, I will assume you are unable to answer it.

Thanks for the lecture. I've done thousands of progressive collapse trials in analytical, computational and simulation environments. You've done how many? I assisted Dr. Benson in converting Keith Seffen's equations of motion to Dr. Bazant's form as part of a future publication submission. Have you even seen Keith Seffen's equations of motions? David Benson's? Bazant's?????

Man, if you know so much about this subject, maybe you can help me with this:


(note to the math savvy: this is an intentionally explicit form to reveal some of the ugly)

This doesn't help your case.

Do you even know what my case is, after I've stated it repeatedly in plain English? Based on the above, I'd have to say no. My points are: Tony is correct about FOS and buckling, you are not. Your fracture theory is not compatible with NIST results, as SnowCrash pointed out. Not everything you say is wrong, but a lot of what's correct is turning out to be either pedantic or misapplied.

Then you accept that it should be discussed honestly? Good.

Of course. I don't care for the manner in which you are discussing it, however. Aside from being wrong on a few important points, you are displaying a certain undeserved condescension which is not sitting well at this time.

Cute.

No, correct.

I said that there's 'some' photo evidence, and provided one photo of it. One is some.

I'm sorry, you've been shifting fluidly and transparently between two incompatible arguments. I was addressing one of them, the notion that NIST backs your fracture scenario. They do not. There is no photographic evidence to support their collapse mechanics. So far, there is exactly one photo offered to support your position, and that is only sufficient to prove existence of fracture, a notion I doubt would stir much surprise around here, least of all with me.

It does not prove your claim, which is that fracture was the dominant mode of failure in the region and time of interest. Not by a long shot. Otherwise, you're stuck with buckling as depicted by NIST, and this does not lead to freefall.

Do I seriously need to go to the trouble of looking at multiple photos? Not interested.

If you want to prove your claim, yes you damn straight will not only have to look at a lot of photos, you'll have to identify the locations of all column ends and show they originate from the area you postulate. All you've shown is fracture has occurred somewhere.

That's what evidence-based research is. See the blurb at the top of the index page? Adhere to it, and identify speculation when doing such. Speculation does not a victory pose make.

It is only contradictory to you, for you don't know the entirety of what I think.

It doesn't matter what you think because the scenarios are objectively seen to be mutually exclusive. That you can hold A and not-A to be true simultaneously is quite a feat, but one which you'll excuse me for not sharing.

I've seen very little discussion of column fracture here. This is the first discussion of it that I know of here.

Imprecision in quantification. Is there "very little" or "none"? None you've seen doesn't mean there is none. You are familiar with traditional logic, I assume. Nevertheless, the possibility remains you are correct. The discussions have centered around the term ductility, not fracture, but they have indeed been few. Maybe because the participants did not wish to speculate, neither commit to the work to show it?

I've actually spent considerable time trying to salvage the situation without invoking speculation, now I'm dinged on it. OK, score one for you.

Virtually all of the discussion has been directed towards the incompatible mechanics of the NIST scenario, or on whether there even IS a period of freefall. Below a certain percentage of freefall, there's not much needing explanation. Forgive me for devoting hundreds of posts to first trying to determine whether or not freefall occurred by doing my own measurements and examining in detail the shortcomings in both NIST's (example, example) and Chandler's methodology (example); and then forgive me attending to other matters once the whole world embraced it as fact as soon as one of the two parties said so.

I'm still not convinced the descent was very near, at, or above freefall.

Joey Canoli wrote:And yet, it's supported by observation of the tower columns, and would very likely be further supported in a photo examination of 7's debris.

It may. Go for it. Until you have, though, you can hardly blame people for favoring NIST's explanation over yours.

Some here seem to think that the sim should be a perfect reproduction of the collapse. How likely is that?

We've come full circle now, back to my original post directed at you.

I wrote:'exactly' is sort of a loaded term when 'country mile' is more the case...

Now it's your turn. Show me any comment where someone has indicated they expect "exact" or "perfect" reproduction. This is a strawman. It reasonable to expect more correspondence than interior collapse followed by global collapse. There is little resemblance. Don't just take my word for it; look at the reaction of JREFers to Enik's collapse sim:

tfk wrote:As far as these value as models are concerned, these are useless. From what can be seen here, they don't seem replicate ANY aspect of the actual collapses.

Makes 'em pretty useless as models, IMHO.

rwguinn wrote:Correlation with reality is an absolute necessity.

This from self-described FEA experts commenting on a WTC1 FEA which collapses. Seems they understand that simply getting a building to collapse does not a valid FEA make. Too bad they also are incapable of applying consistent logic to the NIST.

Joey Canoli wrote:I have learned quite a bit about some people here.

Not about me, I assure you. If you choose to hang around, you will - I assure you.

I will also add that all the JREF experts concluded that horizontal scale deflection must have been used, otherwise the sim bears no resemblance to reality. Get that? The "experts" were absolutely convinced that the contortions were exaggerated because otherwise the sim is a cartoon, like what they're calling Enik's work.

So long as they believed there was (hugely) exaggerated scale, the story was the sim matched exactly. When they found out there was no scaling, suddenly the entire NIST objective changed from modeling the collapse to comparative modeling of... something, I don't know what.