Analysis of WTC collapses by Nemec and Suranova

[Seymour Butz]

I have question.

I work in a 6 story office building that has a pyramid shaped roof consisting of glass panes, which resides over the atrium in the center of the building.

Could I use the formula in this paper to show that a bowling ball dropped from 200' above should just bounce off the roof?

But of course, cuz it;s a well known science fact that even a moon sized pile of rubble would bounce off also...

 

[ozeco41]

IMO, the model they use is incorrect to try and explain what REALLY happened...

Exactly!!!

Which is why it is a tactical error for Ivan to try rebutting them down the rabbit hole they have dug. Their paper does not refer to WTC collapses which occurred on 9/11 so modifying parameters in their fancy looking maths is a waste of time.

I noted the "fancy looking equations" problem coming from the "truther" side in my very first post on the Internet directed at WTC collapse:

Re: World Trade Center? What Really Happened?

The supporters of 9/11 conspiracies build on the same foundation as the creationists - poor logic, worse science together with distortions, lies and deliberate deceptions.

The paper referenced as Engineering Reality by Tony Szamboti is typical of many which look impressive in detail to the non-engineer. The complex calculations may even be correct but the base premises are faulty and the resulting conclusions can readily be demonstrated to be totally wrong.....[followed by all my reasoning]

.... that was me posting as econ41 on the Richard Dawkins Forum » Tue Nov 13, 2007 9:22 pm
... and it was a truther example but the academics are notorious for getting their noses so close to the mathematics that they forget what they are supposed to be doing.

Pictures allegedly speak a thousand words (and I am strongly NLP "visual") so I followed up a few posts later with a crude graphic:

...I'm not much of a graphics artist - and I would draw it differently if I did it now given my improved understanding. But it was good enough for the purpose back then in 2007. If I had labelled it ROOSD I may have become more famous.

And, here we are, nearly into 2013, still seeing our colleague debunkers prepared to debate truthers on the false premises erected by the truthers.

So it's your turn to say it again Gamolon:

...The lower part of the building cannot be used AS A WHOLE to determine the resistance to the upper part.

It's not a solid block hitting a solid block.

And I would like a dollar for every time I have explained that plus 25 cents for every time other members here have done so...

So don't play their games Ivan - they will keep you going round in circles...

 

[Gamolon]

Exactly!!!

Which is why it is a tactical error for Ivan to try rebutting them down the rabbit hole they have dug. Their paper does not refer to WTC collapses which occurred on 9/11 so modifying parameters in their fancy looking maths is a waste of time.

I noted the "fancy looking equations" problem coming from the "truther" side in my very first post on the Internet directed at WTC collapse:

.... that was me posting as econ41 on the Richard Dawkins Forum » Tue Nov 13, 2007 9:22 pm
... and it was a truther example but the academics are notorious for getting their noses so close to the mathematics that they forget what they are supposed to be doing.

Pictures allegedly speak a thousand words (and I am strongly NLP "visual") so I followed up a few posts later with a crude graphic:
[qimg]http://conleys.com.au/webstuff/003.jpg[/qimg]
...I'm not much of a graphics artist - and I would draw it differently if I did it now given my improved understanding. But it was good enough for the purpose back then in 2007. If I had labelled it ROOSD I may have become more famous.

And, here we are, nearly into 2013, still seeing our colleague debunkers prepared to debate truthers on the false premises erected by the truthers.

So it's your turn to say it again Gamolon:
And I would like a dollar for every time I have explained that plus 25 cents for every time other members here have done so...

So don't play their games Ivan - they will keep you going round in circles...

Wouldn't using this scenario...

I have question.

I work in a 6 story office building that has a pyramid shaped roof consisting of glass panes, which resides over the atrium in the center of the building.

Could I use the formula in this paper to show that a bowling ball dropped from 200' above should just bounce off the roof?

...refute their calculations, claims, model? You could even replace the glass panes with aluminum foil.

 

[ozeco41]

Wouldn't using this scenario...



...refute their calculations, claims, model? You could even replace the glass panes with aluminum foil.

Sure but I am probably more stubborn than most members who post here in refusing to accept reversal of burden of proof. Their scenario is wrong in that it is not the collapse which occurred at WTC on 9/11 so refuting their calculations is of no interest to me. I prefer not to even give credibilty to their fundamental error. Plenty of other members here enjoy rebutting such calculations - thereby giving some appearance of legitimacy to illegitimate claims.

We even have long and detailed threads plus an experiment rebutting "thermXte found in the dust". It doesn't matter if there was thermXte in the dust or in 100 tonne stockpiles at each corner of the towers. There was no demolition so thermXte is irrelevant. (Disclaimer: Since I respect those persons who were involved I did contribute to the testing costs )

Ditto the calculations of Nemec and Suranove are irrelevant. As were the calculations by Tony Sz in that 2007 paper I quoted...

/end-ozeco-pedantry

 

[Ivan Kminek]

Thanks to all I am not actually discussing this stuff with Czech truthers, I just gave them the link to this thread, so it's up to you. I have also invited the main author I. Nemec to discuss here, but he seems to be too busy at least during the Christmas time.

Reading this thread again, I'm still not sure if we (well... you) can present some comprehensive critic.

Some points I (perhaps) understand so far:

- The model based on the resistance of columns is highly unrealistic; connections between floors and columns were much weaker structural elements; hence, the resistance of the parts of the towers below impacts was much lower than when derived from the columns resistance. It seems to be clear to me

- As Newtons Bit noted, the scattering of resulting times/heights of collapses in Table 1, when introducing various values of s and α, is anyway huge (height x is from 18 to 331 m); and when using "s = 2 and a = 0.147 you show that the collapse is complete and takes 15.7 s", i.e. a time close to the real collapse time. I would say, therefore, that results are hardly telling anything conclusive, and the value 80 m, after which collapses would stop, is just "arbitrary".

- Used model of the impact of moving upper part on motionless solid lower part is unrealistic. As Ozeco pointed out: "It's not a solid block hitting a solid block." But what it can actually mean as for the expected behavior of buildings? (Sorry that I am so uninformed)

It's quite probable that I still miss some important points.
Now imagine that you are obliged to formulate some very short review of this short paper, readable also for laymen as me. How would you write such a review?

 

[ozeco41]

...Now imagine that you are obliged to formulate some very short review of this short paper, readable also for laymen as me. How would you write such a review?

I wouldn't write it unless I was "obliged' to do so.

If obliged to write this is what I would say.

REVIEW.
Of the paper entitled "DYNAMIC ANALYSIS OF FALL OF A HIGH BUILDING" and authored by Ivan Nemec, Martina Juranova, I. Sevcik 3, P. Frantik4 and Z. Vlk.

The paper in its Abstract claims that is "simulation of the collapse of the WTC building" however the collapse mechanism used in the analysis is not the machanism of the collapse of the WTC Twin Towers.

Therefore the conclusions of the paper are not valid. <<<The Review could Stop at this point.

Optionally you could provide a bit of explanation so try this >>>
The WTC Twin Towers both collapsed by a mechanism with two clearly defined stages:
A) A fire and impact damaged zone became weakened to the extent that it could no longer support to portion of building above that level. That top portion of building started to fall - this process can be referred to as "collapse initiation"; THEN
B) The tower underwent a rapid "global collapse".

The referenced paper starts the analysis with the tower top part already falling therefore the analysis does not apply to the "collapse initiation" stage. It refers only to the "global collapse" stage.

The "global collapse" stage started with the top portion of tower falling therefore all columns had failed and the falling top portions of column were passing their lower sections. The "global collapse" comprised three distinct mechanisms:
1) A pancaking style collapse down the open office space formed by the unique "Tube-in-tube" design which removed the floor joists and left the outer tube columns without bracing in the"radial to building" direction;
2) The outer perimeter columns were thereby left in an unstable condition and peeled off and fell outwards away from the building. There is clear visual evidence of this mechanism which shows that the columns were not buckled and that the resistance offered by those columns was mostly from shearing off of floor connections and possibly some minor friction. The total resistance being far less than the columns would have resisted is axially loaded to buckling; AND
3) Whilst hidden in the dust cloud the core columns like the outer perimeter did not offer much resistance - mostly coming from the forces shearing off the horizontal beams in the core area. That fact available to simple reason despite the absence of visual evidence.

The paper assumes axially loaded columns buckling under those loads was the main force resisting the collapse. That assumption is false - axial loading of columns with forces of the magnitude needed to cause buckling failure simply did not happen at WTC1 and WTC2 on 9/11.

Therefore the conclusions derived from the assumption are worthless.

Anyone considering reading the paper as a contribution to understanding of the actual WTC collapses on 9/11 is wasting their time.


Ivan -- Yes you said brief - I could probably get the verbiage down to about half that length but.....

 

[Africanus]

I've got one question about the fundamental equation of the Nemec article. His fundamental equation is

G - F_N - F_m - F_C - F_a = 0

with

G: gravity force of the falling mass; G = mgb

F_N: column resistance

F_m: resistance of the motionless mass; F_m =mv²
F_C: viscous damping; F_C = mav

F_a: inertial force of the falling mass; bmv(dv/dx)

My question: Is this a valid ansatz? I have two problems with it:

1. He uses the force of gravity for the falling mass. As g is (nearly) constant in the gravity field of the earth, the initial force of the falling would be constant, too. This means that this force is independent of the drop heigth.

2. There are four forces that are directly proportional to the velocity of the falling mass. In contrast to G, this forces depend on the drop heigth of the falling mass, as v = sqrt(2gh). This means, that this forces are directly proportional to the drop heigth and increase with increasing drop heigth.

So if we apply this model, the fall of the mass should be stopped earlier if the drop heigth is increased. This seems to be quite absurd.

Could someone tell me, if my reasoning is correct and explain my error, if it is false?

 

[Lenbrazil]

BTW, I notice that this paper hasn't exactly swept up the engineering community since it was published last year.

Not in the least bit surprising, what's odd though is that it is being ignored by toofers, no sign of it on 911blogger or even AE911T

A little expanded paper was just published in the Journal of Mechanics Engineering and Automation, Volume 2, Number 6. Its online version is available on internet.

I wasn't able to find this paper. The last issue I found was Number 4.

http://www.sapub.org/journal/archive.aspx?journalid=1030

Can you post the link to this paper? You can take out "http" for instance

BasqueArch's link now leads to #6, no sign of the paper.

This is odd, why are truther's ignoring the paper, do even they realize how flawed it is? Even so if it was slated to be published in a legitimate peer reviewed engineering journal why not crow? OTOH it's had to believe Juranova would tell such a bold faced lie, especially one so easily confirmed. The only thing I can figure is that the journal gave some sort of preliminary green light then changed its mind but no one sent her the memo.

BTW - Ivan have you ever run into a crazy American in your country named Peter Lemkin?

 

[Lenbrazil]

Turns out that is is an "open" journal

http://www.sapub.org/journal/charges.aspx?journalid=1030

The authors all seem to be from Eastern Europe or developing countries.

 

[MileHighMadness]

The paper assumes axially loaded columns buckling under those loads was the main force resisting the collapse. That assumption is false - axial loading of columns with forces of the magnitude needed to cause buckling failure simply did not happen at WTC1 and WTC2 on 9/11.

So ozeco41, how did the columns fail...

Fire does reduce the Modulus of Elasticity of steel, which can lead to buckling failure.

 

[Newtons Bit]

Thanks to all I am not actually discussing this stuff with Czech truthers, I just gave them the link to this thread, so it's up to you. I have also invited the main author I. Nemec to discuss here, but he seems to be too busy at least during the Christmas time.

Reading this thread again, I'm still not sure if we (well... you) can present some comprehensive critic.

Wait, what? I did...

 

[Oystein]

I've got one question about the fundamental equation of the Nemec article. His fundamental equation is

G - F_N - F_m - F_C - F_a = 0

with

G: gravity force of the falling mass; G = mgb

F_N: column resistance

F_m: resistance of the motionless mass; F_m =mv²
F_C: viscous damping; F_C = mav

F_a: inertial force of the falling mass; bmv(dv/dx)

My question: Is this a valid ansatz? I have two problems with it:

1. He uses the force of gravity for the falling mass. As g is (nearly) constant in the gravity field of the earth, the initial force of the falling would be constant, too. This means that this force is independent of the drop heigth.

2. There are four forces that are directly proportional to the velocity of the falling mass. In contrast to G, this forces depend on the drop heigth of the falling mass, as v = sqrt(2gh). This means, that this forces are directly proportional to the drop heigth and increase with increasing drop heigth.

So if we apply this model, the fall of the mass should be stopped earlier if the drop heigth is increased. This seems to be quite absurd.

Could someone tell me, if my reasoning is correct and explain my error, if it is false?

False.

Force gives rise to acceleration. Indeed, if you drop something from a greater height, the upward force it experiences when it hits a structure is greater, and thus deceleration is greater, but as the fall is coming from a greater velocity, greater deceleratrion doesn't mean a greater proportion of v will be reduced.

Also, a faster object will also pass the length through which it experiences resistance from a given bit of structure in less time, and thus, while deceleration is greater, it is applied a shorter time.

When you crunch the numbers you will find that, even though deceleration is greater for greater v, the resulting v, after collision and buckling, is still greater. At least up to some limit for v.

Now, as deceleration increases with increasing v, you will eventually come to a situation where deceleration is = -g, so net acceleration will be 0, v remain constant. Let's call that velocity v_end. If you start out with v > v_end, then you will experience a net deceleration, and v will approximate v_end coming from the other side.

The real question is, and really what these people claim: Is v_end = 0?

 

[Africanus]

False.

Force gives rise to acceleration. Indeed, if you drop something from a greater height, the upward force it experiences when it hits a structure is greater, and thus deceleration is greater, but as the fall is coming from a greater velocity, greater deceleratrion doesn't mean a greater proportion of v will be reduced.

But this is indeed my critique! Nemec doesn't take the velocity of the falling mass into account, instead he uses the weight of the upper block, which is independent of the object velocity, as initial force. This is in marked contrast to Dave Thomas attempt, his ansatz, posted here includes the velocity of the falling mass:

F_Dynamic = sqrt(mK2gh) = sqrt(mK) * sqrt(2gh)

The bolded part equals the velocity of the falling mass.

 

[Ivan Kminek]

Wait, what? I did...

Sorry, your nice post was close to some short review. But my point was basically: could we formulate some "joint critic" of the paper, in which all agree? Never mind, it's not important anyway
Btw, Czech truthers argue again in sense: why we should read/take seriously any objections of some anonymous "debunkers" on JREF, with avatars like "Maya the Bee"()? In this regard, who has a qualification in structural engineering or similar (just for the case that I. Nemec would like to discuss his stuff here, which is not probable)?

Ozeco: thanks again I understand, but is this overall "picture" of collapses you presented something, which is generally accepted by "normal" engineering community? I mean: could it be used in the review?

As for international conferences, in which the paper has been presented so far, they were held in Svratka, Velke Bilovice and Zilina - two of them in Czech Republic, one in Slovakia, but basically all of them in former Czechoslovakia. But this is just a remark, it does not mean that these conferences were not "international" or were marginal or so. And it is strange that the paper has not appeared yet in the journal as announced by Martina Juranova. Perhaps just some unexpected delay?

 

[pgimeno]

Turns out that is is an "open" journal

http://www.sapub.org/journal/charges.aspx?journalid=1030

"Open" as in "pay to publish" just as Bentham?

 

[Lenbrazil]

"Open" as in "pay to publish" just as Bentham?

Both, it is my understanding that all or at least most, open journals charge publication fees to pay expense. I went through the papers in the latest edition, one was by authors from France, a few by authors from the former Soviet Block but most were from developing countries. Bentham Open journals had (and I imagine still have) a similar geographic distribution for its authors.

The rationalization they give is that "articles receive the highest exposure and potential impact associated with open access publishing," but it is my understanding is that most, if not all, scientists who matter will have access to important traditional journals.

 

[booNyzarC]

I wouldn't write it unless I was "obliged' to do so.

If obliged to write this is what I would say.

REVIEW.
Of the paper entitled "DYNAMIC ANALYSIS OF FALL OF A HIGH BUILDING" and authored by Ivan Nemec, Martina Juranova, I. Sevcik 3, P. Frantik4 and Z. Vlk.

The paper in its Abstract claims that is "simulation of the collapse of the WTC building" however the collapse mechanism used in the analysis is not the machanism of the collapse of the WTC Twin Towers.

Therefore the conclusions of the paper are not valid. <<<The Review could Stop at this point.

Great writeup you've provided here Ozeco, but I have a question for the sake of clarity.

Would you apply the same reasoning to Bazant's limiting case?

For me, Bazant's limiting case suffers from the same criticism you apply, however I find it of value and completely relevant. If Bazant's inputs and calculations are accurate (which I believe they are) his case proves global collapse under the best case scenario. Should we not apply the same uniformity of logic to this paper?

In my opinion this paper fails because the inputs and calculations are inadequate, not because it fails to mimic the nature of the actual collapse events.

Cheers.

 

[Oystein]

Great writeup you've provided here Ozeco, but I have a question for the sake of clarity.

Would you apply the same reasoning to Bazant's limiting case?

For me, Bazant's limiting case suffers from the same criticism you apply, however I find it of value and completely relevant. ...

Ozeco will surely respond to this, but to relieve you of the suspense here's a preview:

Bazant has written at least four papers. The limiting case you allude to was the first - Bazant and Zhou, 2002, which was originally conceived and written within days of 9/11. Yes, this limiting case is valid within the constaints it mentions. Even though Bazant has a few numbers probably wrong (for example, iirc, he assumes a total mass of one tower of 500,000 tons, but they were probably <300,000 each, which would improve survival chances. From 0 to 2x0 in that case )

Subsequent Bazant papers model in more and more detail, and thus indeed fail for the same reason Nemec and Juranova fail: He keeps focussing on column behaviour, allthough that wasn't the predominant failure mode or path of resistance. Interesting perhaps and well worked-out in their own right, they just shouldn't be applied to the reality of the WTC collapses, or with utmost care.


In my opinion (don't know what ozeco's is), some aspects of Bazant, Greening, Le and Benson are valuable; their take on concrete comminuition (sp?), air ejection, measurement of collaps speed etc. were improvements on things incorrectly or imprecisely claimed by truthers.

 

[GlennB]

The paper assumes axially loaded columns buckling under those loads was the main force resisting the collapse. That assumption is false - axial loading of columns with forces of the magnitude needed to cause buckling failure simply did not happen at WTC1 and WTC2 on 9/11.

So ozeco41, how did the columns fail...

Fire does reduce the Modulus of Elasticity of steel, which can lead to buckling failure.

By stripping away the lateral support, the columns became effectively weaker than in their original condition. Then there were lateral forces being applied by falling debris to these now 'more slender than they used to be' columns.

 

[booNyzarC]

Ozeco will surely respond to this, but to relieve you of the suspense here's a preview:

Bazant has written at least four papers. The limiting case you allude to was the first - Bazant and Zhou, 2002, which was originally conceived and written within days of 9/11. Yes, this limiting case is valid within the constaints it mentions. Even though Bazant has a few numbers probably wrong (for example, iirc, he assumes a total mass of one tower of 500,000 tons, but they were probably <300,000 each, which would improve survival chances. From 0 to 2x0 in that case )

Subsequent Bazant papers model in more and more detail, and thus indeed fail for the same reason Nemec and Juranova fail: He keeps focussing on column behaviour, allthough that wasn't the predominant failure mode or path of resistance. Interesting perhaps and well worked-out in their own right, they just shouldn't be applied to the reality of the WTC collapses, or with utmost care.


In my opinion (don't know what ozeco's is), some aspects of Bazant, Greening, Le and Benson are valuable; their take on concrete comminuition (sp?), air ejection, measurement of collaps speed etc. were improvements on things incorrectly or imprecisely claimed by truthers.

I understand and agree with much of what you're saying here, however I disagree on the point of failure in Bazant's limiting case (which is comprised of more than one paper, yes.)

Bazant was providing a best case scenario, he was not attempting to accurately model the actual collapses. The question answered in his papers is regarding the inevitability of global collapse once collapse is initiated. By discussing column behavior, he is discussing the components with the most potential resistance to a global collapse, and if global collapse ensues despite this it will ensue under any circumstance.

The only point of contention which could be considered legitimate regarding his limiting case is whether or not it truly represents a best case scenario in favor of building survival. If anyone can establish that it does not, they would essentially render his conclusions about the inevitability of global collapse invalid. Nobody has accomplished this to my knowledge, though many have tried and failed.

And even if one were to determine that his case was not in fact a limiting case (i.e. best case scenario in favor of building survival), it still would not support the impossibility of global collapse; that would require much much more.

Hope that clarifies.

Cheers.