Analysis of WTC collapses by Nemec and Suranova

[Martina Juranova]

I'm not suggesting you didn't account for it. I'm saying that your accounting didn't allow for the columns fracturing at any point, and so was a very great overestimate.



Then you got your calculation wrong. Many conservation of momentum analyses have been done, and all give collapse times close to or slightly less than the observed collapse time. If everyone agrees except you, I suspect it might not be everyone else who's wrong.



Kuttler's paper is utter nonsense, and blatantly dishonest as well. My comments on it are here.

Dave

The coefficient κ which we have introduced, is the ratio of the average normal force in the column and its ultimate force, so also fractures can be included. But because steel is not fragile material, this influence probably will not be substantial. But I would not argue if you regard the value of κ lower, than 0.25 which we had assumed as the probable value.

As regard the limit case, where no resistive forces, except inertial forces are taken into account, this is fully described including the resulting formula in the paper mentioned in my first contribution. For the same data as was used by Prof. Kuttler we have obtained very similar value of the time of the collapse.

K. Kuttler’s approach is correct. There could be some controversy only about some his quantitative estimations. But his thesis, that the complete destruction of such an enormous structure (i.e. pulverization of concrete and plastic yield and fracturing of steel), must be at the expense of kinetic energy of fall, is indisputable.

 

[DGM]

What else could it be? E.g. a controlled demolition. But we don’t want to speculate.

How about space beams or Mothra?

 

[The Big Dog]

Ad 1) No structure is completely isolated. But the principle of isolation was known already to the founder of mathematical mechanics Archytas of Tarentum and is still widely used in analyzing structures. We could add to our solution e.g. aerodynamic drag, probably the most important influence not taken into account. The differential equation would be a little more complicated. Nevertheless the pertinent force would act against the motion and would cause further slowing of the collapse.

Ad 2) No substantial parts of the core remained standing after the initial collapse. When seeing the videos we cannot see any standing columns above the front of the destruction except the lower part, where only several columns remained standing.

Ad 3) Sorry, I don’t understand the word „verinage“.

1. drag? the most important influence not taken into account? Are you *********** with me? That is ridiculous. Did you think the structure below the collapse front was floating or something?

2. Wrong. Seriously? Wrong.

3. I get that now.

Thanks for posting.

 

[carlitos]

Vérinage is a technique where the top part of a building is dropped on the bottom part to achieve demolition. No explosives are used; the supports are pulled with hydraulics.

 

[ergo]

My first is in EGO, but isn't in PHONE
My second's in CORNER but never in CONE
My third and fourth letter are both in EVADE
My third's not in DEVIL, the fourth's not in SHADE
My fifth's found in RING, not however in GROUND
My sixth is in PETAL, but in LEAP won't be found
My last is in PARTY, but in TRAP doesn't fit
Good luck with this riddle, you thick truther ****

Yes, very well done, and an excellent way to distract from the fact that you didn't answer my question. In what way is momentum not conserved in the modeled collision?

 

[ergo]

And thank you, Dr.? Ms.? Juranova for suffering these fools so diplomatically.

 

[Horatius]

Vérinage is a technique where the top part of a building is dropped on the bottom part to achieve demolition. No explosives are used; the supports are pulled with hydraulics.

Nice video! Now, Martina should attempt to apply the analysis used in this paper to these examples, so see if the methodology can accurately predict the collapses as shown.

 

[The Big Dog]

Yes, very well done, and an excellent way to distract from the fact that you didn't answer my question. In what way is momentum not conserved in the modeled collision?

Here was the statement:

"I was thinking this myself. I can understand why amateurs writing nasty comments on Youtube videos would make the mistake of applying the Law of Conservation of Momentum to the collapse of the Twin Towers. However, hearing an alleged engineering expert make the same mistake makes me wonder whether this "expert" either doesn't know what the LoCoM is or assumes her audience doesn't.

Either way, poor work."

Here is your question:

"How does the modeled collision not conserve momentum?"

You are missing something aren't you? I'll answer: the collapse of the towers was not an isolated system.

 

[Oystein]

Nice video! Now, Martina should attempt to apply the analysis used in this paper to these examples, so see if the methodology can accurately predict the collapses as shown.

Good idea! If the paper is good science, it should be able to predict the situation of Verinage demolition!


I also wonder if Martina is still thinking about how to reply my most recent post here - where I argued a point diametrically opposed to what she believes: That the observable collapse, as per both video evidence and study of the steel debris, indicated that the dominant mode of collapse progression was a run-away failure of office floors which failed at the floor-to-column connections, and NOT failure of columns, or column-to-column connections.

 

[Oystein]

...
Here is your question:

"How does the modeled collision not conserve momentum?"

You are missing something aren't you? I'll answer: the collapse of the towers was not an isolated system.

For those whose main skills do not include high-school-level physics:

As the mass of falling material accelerates, momentum is "stolen" from planet earth, by interaction through the pull of gravity. As the mass of falling material decelerates, and finally comes to a full stop on the ground, momentum is returned to planet earth through inelastic collisions. Before that falling mass hits the ground, momentum would be transfered to planet eartn through intact columns rooted in the ground.

 

[The Big Dog]

For those whose main skills do not include high-school-level physics:

As the mass of falling material accelerates, momentum is "stolen" from planet earth, by interaction through the pull of gravity. As the mass of falling material decelerates, and finally comes to a full stop on the ground, momentum is returned to planet earth through inelastic collisions. Before that falling mass hits the ground, momentum would be transfered to planet eartn through intact columns rooted in the ground.

How did those beams get up there in the first place? And where did all that "work" go to get them there?

Further, are we assuming that the connections to the columns can transfer the momentum to the columns before they fail?

 

[Oystein]

How did those beams get up there in the first place? And where did all that "work" go to get them there?

I think you are now talking about potential energy.
I was talking about momentum.

Further, are we assuming that the connections to the columns can transfer the momentum to the columns before they fail?

Yes, we are assuming that.
In fact, we know that the connections to the columns can transfer the momentum to the columns ONLY before they fail.

 

[thedopefishlives]

How did those beams get up there in the first place? And where did all that "work" go to get them there?

Further, are we assuming that the connections to the columns can transfer the momentum to the columns before they fail?

Essentially, what Oystein was saying is that the "closed system" required for conservation of momentum includes the Earth, which supplies the gravitational force required for the collapse. Looking at just the tower itself, there is an external force that violates the prerequisite for conservation of momentum to hold.

 

[Newtons Bit]

The coefficient κ which we have introduced, is the ratio of the average normal force in the column and its ultimate force, so also fractures can be included. But because steel is not fragile material, this influence probably will not be substantial. But I would not argue if you regard the value of κ lower, than 0.25 which we had assumed as the probable value.

I don't know if this is a language barrier or not, but the word you're looking for is axial force. A force normal to the column could be acting along any of the principal axes.

Considering that the columns have buckled at about 0.02 strain and shortly thereafter every connection from the column to the reset of the building would fracture. At that point, the tortured remains of the column would not provide any resistance whatsoever to the collapsing structure. Using 25% of the ultimate capacity of the columns over the entire length of the building is exceedingly optimistic for collapse resistance. Even using a method such as one by Bazant and Zhou, a factor of 0.25 would not be achieved.

Your definition of s is sorely lacking. It appears all it does is serve to increase kappa from 0.25 to 0.5 and 0.75.

Your results are all over the place. You state that the collapse terminates at 80cm, but none of the results in table 1 show this. The distance x varies from 18.2m to 331m. With s = 2 and a = 0.147 you show that the collapse is complete and takes 15.7s. How can you possibly claim that the collapse should have arrested?

 

[The Big Dog]

I think you are now talking about potential energy.
I was talking about momentum.


Yes, we are assuming that.
In fact, we know that the connections to the columns can transfer the momentum to the columns ONLY before they fail.

So we are not talking about a closed system

 

[Oystein]

So we are not talking about a closed system

Right! I think you misunderstood: In my post #50 I explained WHY the towers weren't closed systems wrt CoM, reinforcing your statement, not criticising or correcting it. With "those whose main skills do not include high-school-level physics" I did not mean you but those who might not understand your post

 

[000063]

How about just answering it with an answer, since your question is not going to help you.

Yes, very well done, and an excellent way to distract from the fact that you didn't answer my question. ...

I'd like to think that someday, you'll realize the irony.

What else could it be? E.g. a controlled demolition. But we don’t want to speculate.

Well, except for all the evidence contradicting a CD, such as the inability of any explosives to reliably function after being hit by a jumbo jet.

 

[pgimeno]

Vérinage is a technique where the top part of a building is dropped on the bottom part to achieve demolition. No explosives are used; the supports are pulled with hydraulics.

And, to be fair, designed to be applied to buildings whose structure consists of parallel load-bearing walls, with no columns and in particular with no steel columns.

 

[pgimeno]

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.

As you've been pointed out already, it was observed. FEMA did a good job in analyzing the videos and noting this. Here's a video that shows the dust ejections due to the pancaking of floors (pay special attention to the corner):



I think it's interesting to note that those who have studied the pancaking say that the videos show the collapse front reaching zero acceleration at some point.

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.

As far as I understand, all you may possibly have shown is that the progression of the collapse does not consist of column to column impacts. Your conclusion is overreaching given the scope of your paper. The actual collapse mechanism is misrepresented in it, thus that conclusion doesn't follow.

 

[Horatius]

As far as I understand, all you may possibly have shown is that the progression of the collapse does not consist of column to column impacts. Your conclusion is overreaching given the scope of your paper. The actual collapse mechanism is misrepresented in it, thus that conclusion doesn't follow.

Yeah, let's remember this. While it's fun to debate the merits of one analysis over another, let's not forget that we're discussing a model of the collapse that no one (outside of a few truthers creating strawmen) actually considers to be anywhere close to valid.