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Analysis of WTC collapses by Nemec and Suranova

Ivan Kminek

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Hi all,
Czech truther(s) asked me if I could assess this paper on WTC collapses of Czech construction engineers Ivan Nemec and Martina Juranova. The title is DYNAMIC ANALYSIS OF FALL OF A HIGH BUILDING, but the paper deals only with Twins.

Since it is way over my head, I promised that I will submit this paper here for some consideration of people who understand these topics. (Juranova wrote whole diploma thesis on this topic, but it seems that it is not available online).

Basically, Nemec and Juranova seem to claim that the collapses of towers should be stopped after several tens of meters.
 
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1. Main problem: Their equations consider only column-on-column impacts. This is not what happened in reality, where most of the mass moved between columns and impacted floors, and broke the floor-to-column connectors, rather than buckling any columns. Obviously, those connections are a lot weaker than the columns themselves, as they are designed to only hold the weight of one floor, and not of the entire building mass above.

2. I don't see that, and how, the two simulation programs make use of the equations they derived. Also, I am missing a lot of explanations on what the input was to those simulations - boundary conditions and all.

3. Just 3 references, none to Bazant, Zhou etc??

4. Poorly edited paper, e.g. at the very end, last reference: "[3] Nemec, I. at all.: ..." :D


ETA: Ivan, it's Juranova, not Suranova ;)
 
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To the extent that it claims to apply to WTC Twin Towers the paper is nonsense.

Unfortunately it shares with a lot of academic "explanations" of WTC collapse one feature:

It has no mechanism which remotely resembles what actually happened with the 'Twins' and, for some reason which I cannot comprehend, academics such as these two seem to think that complex formulas or FEA's or whatever theory they are pushing are of value and over-ride what really happened. I have news for such theoreticians - first they should not be let loose outside their cloisters of academia - but let's stay polite and leave out references to the faeces of the male bovine......

Put politely I disagree. Any theoretical explanation which ignores reality will IMNSHO either be:
1) Wrong; OR
2) Right for the wrong reasons and therefore even more misleading.

...and I have not seen a example of 'right for the wrong reasons' in this sort of paper.

Put more explicitly the single specific reason that the paper is nonsense is that it considers column resistance as a main factor. Reality of 9/11 was that post 'initiation' of collapse column resistance was not a significant factor. And that bit of reality is the key to understanding the global collapses of the twins. People who do not recognise that simple reality are bound to be wrong. These two academics are wrong.

Next question. :rolleyes:





PS - The terseness of the above reflects Friday PM after a tiring week and most way through a bottle of wine.

More detailed explanation available if needed - :o :) ;)

PPS Oystein already did a better job of the engineering part of the explanation - He is right and has identified the key issues. :blush::blush:
 
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Oystein said:
1. Main problem: Their equations consider only column-on-column impacts. This is not what happened in reality, where most of the mass moved between columns and impacted floors, and broke the floor-to-column connectors, rather than buckling any columns. Obviously, those connections are a lot weaker than the columns themselves, as they are designed to only hold the weight of one floor, and not of the entire building mass above.
Click to expand...

The criticism of Bazant's "back of the envelope calculation" over assuming column-on-column impacts was misplaced, since it was an idealized boundary condition. But it surely does apply to this paper. BTW, I notice that this paper hasn't exactly swept up the engineering community since it was published last year.
 
Oystein said:
1. Main problem: Their equations consider only column-on-column impacts. This is not what happened in reality, where most of the mass moved between columns and impacted floors, and broke the floor-to-column connectors, rather than buckling any columns. Obviously, those connections are a lot weaker than the columns themselves, as they are designed to only hold the weight of one floor, and not of the entire building mass above.
etc.
Click to expand...

It is quite amazing that 10 years+ after the fact that this very simple and very easy concept to envision, even by non-engineers such as myself, continues to be misrepresented or willfully ignored by others.
Its the first condition Bazant considers, is it not?

Methinks someone is trying to get a diploma without doing much work.
 
There's two problems I notice, that people more knowledgeable should check me on. First off, they're using this as the fundamental equation behind their model:

We will introduce equation of dynamical equilibrium for
the location x:
G - Fn - Fm - Fc - Fa = 0 (1.1)
G is weight of a part of the building above the location x,
for which equilibrium equation is formulated
Fn is resistance put up by the columns against the collapse
Fm is resistance originated by hitting of a falling part of the
building into a motionless mass
Fc is a viscous damping
Fa is an inertial force of a falling mass
Click to expand...



The "point x" they're discussing seems to be some arbitrary point below the point of initial failure (which is designated x=0 point in the accompanying diagram).

So they've assumed there's some point at which the forces will balance out. But isn't that pretty much what they were trying to prove in the first place?

Also, if the forces are balanced out, all that means is that the acceleration of the collapse will be zero, not that the collapse itself stops (which would require zero velocity, not just zero acceleration).

Secondly, they're subtracting Fa from G, the force of gravity. Fa is defined as:


e) The inertial force of a falling mass:

(Delete equation, format is screwy)

Again, only the inertial force of a mass which does not fall outside of the building is
considered here.
Click to expand...


Why is the force due to the falling mass being subtracted from the force due to gravity? Wouldn't this force be added to G, thus increasing the likelihood of collapse?



Also:

(Juranova wrote whole diploma thesis on this topic, but it seems that it is not available online)
Click to expand...


If that's true, then there certainly would be some sort of critique of their methods by their own instructors. Has anyone tried to find out how that went? I suspect that critique would be far more detailed and accurate than anything we could tell you.
 
Horatius said:
There's two problems I notice, that people more knowledgeable should check me on. First off, they're using this as the fundamental equation behind their model:





The "point x" they're discussing seems to be some arbitrary point below the point of initial failure (which is designated x=0 point in the accompanying diagram).

So they've assumed there's some point at which the forces will balance out. But isn't that pretty much what they were trying to prove in the first place?

Also, if the forces are balanced out, all that means is that the acceleration of the collapse will be zero, not that the collapse itself stops (which would require zero velocity, not just zero acceleration).

Secondly, they're subtracting Fa from G, the force of gravity. Fa is defined as:





Why is the force due to the falling mass being subtracted from the force due to gravity? Wouldn't this force be added to G, thus increasing the likelihood of collapse?



Also:




If that's true, then there certainly would be some sort of critique of their methods by their own instructors. Has anyone tried to find out how that went? I suspect that critique would be far more detailed and accurate than anything we could tell you.
Click to expand...

Fa is due to the acceleration of the top reference frame with reference to the bottom static reference frame and it is negative because they set x=0 at the point of initiation. Wiki helps puzzle it out here.
 
Thanks to all:) Czech truthers have got a link to this thread, and they can even send your reactions to I. Nemec.
 
Btw, I'm now writing another article in Czech on 9/11 conspiracy theories for one science-fiction magazine, quite naturally with some emphasis to paints and thermites:o)

Since I'm too lazy to do some research, could you pls give me some info, how many (if any, except Harrit's paper) truthers papers were published in some scientific journals (including open journals)?

(Meanwhile in China: fresh video of simultaneous controlled demolition of two high buildings . It seems that in these cases, explosive charges were planted in three floors of these buildings, separated by ca 6 floors without charges (?).
 
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.

The presented theory of dynamics of the collapse of high building is based on the law of conservation of momentum, which is one of the fundamental laws of mechanics. Its expression is the equation of the dynamic equilibrium. The paper introduces a differential equation based on this principle. This equation deals with the main forces that act on the mass on the front between both the falling and the motionless masses. Several parameters influencing quantity of the forces are introduced. The magnitude of these parameters can be discussed. The fall will be decelerating and extent of the collapse would be about 70-80 m when setting the magnitude of the parameters to values that authors consider as probable. The whole building would fall in a limit case when omitting all of the resistances except for one based on deceleration of a falling mass hitting another motionless mass; i.e. columns do not resist to the collapse at all and no mass fell outside of the building. Speed of the collapse would be much slower than it was observed in this case, however. Prof K. Kuttler, who published in the Journal of the 9/11 studies (2006) the paper “A short computation”, has obtained almost same results as the authors of the paper mentioned above. These results are indisputable because all of the resistances except for motionless mass were omitted and only the law of conservation of momentum was applied. Then the only presented conclusion can be that the falling mass could not hit the motionless mass. Instead it could only hit the mass which has already started moving prior to the impact with the falling mass.
Some remarks to the contributions of the discussion:

To Oystein:
You have mentioned the so called “pancake collapse”, where one or more falling slabs hit another slab. The connections are broken and a further slab is falling. This could have happened, but it was not observed. The inner core of the building, where were no slabs (only columns), would remain standing in such a case. Acceleration of the collapse would be much slower than it was observed, as well.
The simulation programs are based on the explicit method. The boundary conditions are simple. The building stands on rigid subsoil.

To Horatius:
When introducing the inertial forces then each body is in a dynamical equilibrium (D'Alembert's principle can be found on wikipedia). This principle also explains why the inertial force of the falling mass has the opposite sign than the gravity force.
Our theory, which was published in the paper, was presented in 3 international scientific conferences and up to now nobody has found a mistake in the theory.

To LSSBB:
Thanks for your explanation to Horatius.
 
Captain_Swoop said:
All very well but they still fell down.

Why do you think that is?
Click to expand...

Probably because the value for column resistance is wildly overestimated. If columns are assumed to deform continuously over 100% of their length, as in the paper, then their resistance will become unrealistically high. In reality, columns may buckle, fracture at plastic hinges, or most likely fracture at splices and bolted connections, giving a very much lower time-average resistance.

Dave
 
To: Captain Swoop

We have only shown, that the cause of the collapse of the Twin towers must be different, than the impact of the planes and fire only. In my previous contribution I have written that the falling mass could not hit a motionless mass, because then the collapse would be slower, even with the omittance of column resistance. The only physical explanation of the observed collapse is, that the mass must have begun to fall before it was hit by the falling mass. The authors of the paper, as academinians and technicians, would like to stand on pure science and not introduce speculations pertaining to the fact that the motionles mass started fo fall before it was hit by the falling mass. But some possible cause you can find on web.

To Dave Rogers

The buckling and yielding of the columns were taken into accont in our solution. It's influence is considered in the coefficient kappa in the differential equation. And as I have written above, even when omitting all column resistance, the speed of the collapse should have been much slower than observed. Our result based on the law of coservation of momentum is congruent with that of prof Kuttler, who based his solution on the law of conservation of energy.
 
So you are 'Just asking questions'?

Seems a bit of a cowardly cop out to me.

Why don't you stand up and say what you think happened you obviously don't think it was a combination of crash damage and fire.

What else could it be?
 
Martina Juranova said:
To: Captain Swoop

We have only shown, that the cause of the collapse of the Twin towers must be different, than the impact of the planes and fire only. In my previous contribution I have written that the falling mass could not hit a motionless mass, because then the collapse would be slower, even with the omittance of column resistance. The only physical explanation of the observed collapse is, that the mass must have begun to fall before it was hit by the falling mass. The authors of the paper, as academinians and technicians, would like to stand on pure science and not introduce speculations pertaining to the fact that the motionles mass started fo fall before it was hit by the falling mass. But some possible cause you can find on web.


To Dave Rogers

The buckling and yielding of the columns were taken into accont in our solution. It's influence is considered in the coefficient kappa in the differential equation. And as I have written above, even when omitting all column resistance, the speed of the collapse should have been much slower than observed. Our result based on the law of coservation of momentum is congruent with that of prof Kuttler, who based his solution on the law of conservation of energy.
Click to expand...

It looks like you used the wrong formula for the inertial force of a falling mass (1.7) Fa= Bma
Where B = portion of the falling total mass above (building mass minus the mass that falls outside of the building)

Dave Thomas calculates this force to be Fdynamic= sqrt (2Kmgh) where h = drop height.
His experiment confirms this formula.

http://www.nmsr.org/nmsr911a.htm

Like Oystein mentioned above, why did you not reference Bazant as you both used the same Ideal Model assumptions, that of simultaneous and square column impacts, which did not happen in the Actual Event.
 
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To me this paper is puzzling at best. Some statements:

1. The resistive force of the columns was defined as

FN = m*g*s*k

But is this equation correct? I think, that m*g equals the weight of the upper part and that s and k are material constants of the columns. But the weigth of the upper part was previously defined as

G = m*g*b

where b is a correction factor as not the total mass of the upper part impacted the lower part. Shouldn't this term be incorporated in FN, too?

2. Could someone explain table 1 to me? I'm not an engineer and I have no clue how to interpret the data of this table.

3. I have the same problems with fig. 4 and 5. What do this colours mean?

4. The most interesting part of the paper:

For the chosen parameters, which the authors believe could be probable, the fall of the building would stop after falling cca 80 m.
Click to expand...

a. Why do the authors believe this parameters to be true?

b. So the upper part is expected to fall 80 m, which equals 21 floors. What happens to these floors?
 
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Martina Juranova said:
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.

The presented theory of dynamics of the collapse of high building is based on the law of conservation of momentum, which is one of the fundamental laws of mechanics. Its expression is the equation of the dynamic equilibrium. The paper introduces a differential equation based on this principle. This equation deals with the main forces that act on the mass on the front between both the falling and the motionless masses. Several parameters influencing quantity of the forces are introduced. The magnitude of these parameters can be discussed. The fall will be decelerating and extent of the collapse would be about 70-80 m when setting the magnitude of the parameters to values that authors consider as probable. The whole building would fall in a limit case when omitting all of the resistances except for one based on deceleration of a falling mass hitting another motionless mass; i.e. columns do not resist to the collapse at all and no mass fell outside of the building. Speed of the collapse would be much slower than it was observed in this case, however. Prof K. Kuttler, who published in the Journal of the 9/11 studies (2006) the paper “A short computation”, has obtained almost same results as the authors of the paper mentioned above. These results are indisputable because all of the resistances except for motionless mass were omitted and only the law of conservation of momentum was applied. Then the only presented conclusion can be that the falling mass could not hit the motionless mass. Instead it could only hit the mass which has already started moving prior to the impact with the falling mass.
Some remarks to the contributions of the discussion:

To Oystein:
You have mentioned the so called “pancake collapse”, where one or more falling slabs hit another slab. The connections are broken and a further slab is falling. This could have happened, but it was not observed. The inner core of the building, where were no slabs (only columns), would remain standing in such a case. Acceleration of the collapse would be much slower than it was observed, as well.
The simulation programs are based on the explicit method. The boundary conditions are simple. The building stands on rigid subsoil.

To Horatius:
When introducing the inertial forces then each body is in a dynamical equilibrium (D'Alembert's principle can be found on wikipedia). This principle also explains why the inertial force of the falling mass has the opposite sign than the gravity force.
Our theory, which was published in the paper, was presented in 3 international scientific conferences and up to now nobody has found a mistake in the theory.

To LSSBB:
Thanks for your explanation to Horatius.
Click to expand...

Couple of questions:

1. "The presented theory of dynamics of the collapse of high building is based on the law of conservation of momentum, which is one of the fundamental laws of mechanics." Doesn't this law only apply to isolated systems? Was the WTC an isolated system?

2. "The inner core of the building, where were no slabs (only columns), would remain standing in such a case." Are you aware that substantial portions of the core remained standing after the initial collapse?

3. Are you aware of verinage demolition?
 
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