Why a one-way Crush down is not possible

[AZCat]

An impulse requires deceleration

It does? I think you're forgetting that the top portion was under a constant acceleration already. Imparting force onto another object would only require that the top portion accelerate at a slower rate, rather than decelerate.

 

[alienentity]

Grizzly, you wrote 'so unless you're arguing that the charges must have been applied in the impact zone' yes, he is. Absolutely.
What else do you expect from this kind of inquiry?

I read very carefully through all three Bazant papers to see where Tony's claim that Bazant calls for a big 31g 'jolt' is, and I didn't find it. Bazant et al DO give a ratio equal to that number for the amount of energy vs the design load capacity.

'The kinetic energy of the top part of tower impacting the floor below was found to be
about 8.4 × larger than the plastic energy absorption capability of the underlying story, and considerably higher than that if fracturing would be taken into account (Baˇzant and Zhou 2002)'

Nowhere do they indicate a massive deceleration or 'jolt'. Instead, they argue that the energy lost would be a small percentage of that available, which is what we expect and what appears to have happened, based on the video evidence.

In their words it's 'the relative smallness of energy absorption capability compared to the kinetic energy' (p3 'Mechanics of Progressive Collapse: Learning from World Trade Center and Building Demolitions ' Bazant and Verdure.

Please note this paper WAS published in Journal of Engineering Mechanics, 2007.

Tony has his knickers in a twist because he's basically nitpicking Bazant's work, (not doing his own original theorizing, please note) and having raised some good questions, immediately leaps to the standard twoofer dogma, throwing his brains out the window as he does so.

He likes to give the impression that he is fully qualified to examine this subject, but gives up immediately because he's apparently let down by Bazant. This intellectual laziness is not good science; it's more troofer dogma dressed in a few equations.

I'd like to see this stuff get published in a respected journal. I doubt it ever will be. Whatever. If this is the best stuff they've got, it's pathetic.

 

[Grizzly Bear]

You've conveniently handwaved the bowed columns into nothing, merely and irrelevant detail for you to ignore. But unfortunately it poisons your entire premise, because it provides the necessary motion to initiate collapse, just not the way you want to see it.

That's just too bad. No explosive squibs, no visible detonations, no controlled demolition. If you don't understand it by now, you never will.

The bowing of the exterior columns were more an indication that the structural integrity of that area was substantially reduced... I agree it's an indication that had I been there, I would have been very worried about whether that structure was stable or not, but as far as I understand it wasn't the mechanism for progression... Assuming I've got what you're referring to correctly...

The problem I find with Tony's jolt argument is not that he argues there was NO jolt, rather the jolt he's asserting should have been blatantly visible on video camera is a mis-characterization of the collapse.

Bazant's model as I understand simplifies the collapse for the purpose of biasing against collapse progression, meaning he has the upper section fall onto the lower section square-on negating axial loads that were inevitably part of the collapses... The collapse wasn't so perfect, and floor systems that were designed for lateral bracing were forced to take on the load of an entire section of the building while it was moving no less... If the floors are the primary obstacles against the collapse... I don't see how Tony's jolt assertion would apply, at least when it concerns the magnitude he states it should have been visible...

The 50 to 60 stories of core columns remaining after the collapse front passed by were only interior core columns. All of the outer core columns, which were the largest columns in the buildings, went down with the collapse front. I don't know how many people realize this.

I've heard about this, but I really don't believe it changes that if the floors were impacted with loads they were very clearly not intended to carry the first components to fail would be the connections that hold them to the core structure. You can argue that parts of the core could have been taken out to facilitate it, but based on my understanding of the tower's construction taking them out would have been wholly unnecessary.

I'm not sure I need to comment on the rest I left out... since I'd be wasting air trying to tell you about some details which you genuinely know... (namely the issue dealing with slenderness ratio and the like with the free standing core)

 

[alienentity]

Tony, I apologize for being hard on you, but you seem unaware that you've fallen into an intellectual trap.

Just because you can't find an explanation yourself (no big deal) you are essentially accusing your government of mass murder. I don't think you understand how terribly irresponsible you are.
You have absolutely NO conclusive proof at all to base your accusation on. Just a misunderstanding of the mechanics of the collapse. Eventually you may see this for yourself.

You already have admitted, in writing, that the energy necessary to destroy the lower floors was available based on gravitational collapse. You've then imposed a phony condition (seeing the jolt on video) to justify and end to any intelligent inquiry (which you're obviously capable of) and a default to the impossible: controlled demolition.

You don't seem to give a rat's behind that it is impossible that the perimeter columns were blown out every 3 floors without us being able to clearly identify that process from video evidence. It didn't happen.
That's how far you've been corrupted by the ideology of CD.

I'm not interested in anything but the truth. Your excuses will not be sufficient to discourage me.

 

[Furcifer]

The 50 to 60 stories of core columns remaining after the collapse front passed by were only interior core columns. All of the outer core columns, which were the largest columns in the buildings, went down with the collapse front. I don't know how many people realize this.

Do you have a source for this? It makes sense but I've never seen an analysis of the free standing core.

 

[tsig]

We don't use the 31g as a basis to calculate the energy losses. The energy losses are a function of the strength of the columns at the top of the lower block and at the bottom of the upper block or on the 97th and 99th floors which are assumed to elastically and plastically deform and then buckle.

Dr. Bazant actually has an error in terms here as Po is the actual design load not the load capacity which would have been at least three times greater due to the factors of safety used in the column design.



There is plenty of valid reason for a massive jolt. How do you think the kinetic energy gets transferred? Why do you think Bazant said there had to be a powerful jolt?



The lack of freefall does not argue against controlled demolition. All it says is that there was some residual resistance remaining. I used an example here the other day where you have a 100 lb. weight supported by 30 columns which can each support 10 lbs. and you then remove 27 of the columns. What happens? The 100 lb. weight fall at 0.7g, not freefall. All that needs to be done is to remove enough columns so that the load above cannot be supported to create the fall.



Please show how the bowing has any import to the continuation of the collapse once it was initiated. It is the continuation of the collapse that the jolt is necessary for, and what the paper addresses.



If you have actually read "The Missing Jolt" paper you would have noticed that we found a significant error in Bazant and Zhou's calculation of the axial stiffness of the columns. They calculate 71 GN/m when it is actually 7.1 GN/m. So they were off by a factor of ten, probably the result of a misplaced decimal point. Using the correct stiffness (C) of 7.1 GN/m in Bazant's equation for overload ratio, gives an 11g Pdyn/Po ratio. In addition to that, I showed you the design load vs. design capacity term error above made by them also, which is somewhat misleading. The columns actually had a capacity of at least 3 times their actual load so now the overload is down to about 367%, not the 3100% Bazant and Zhou show. So much for your credits of mathematical superiority to the Bazant papers over the one I was involved in.

Admittedly, a 367% overload ratio is more than sufficient but how do you transmit it to the lower structure? The answer is that there must be an impulse with it's requisite deceleration to transfer the kinetic energy. If there is no deceleration there is no 367% overload. Bazant knew this and that is why he felt there must have been a very powerful jolt. He just never measured for it. When someone finally measured for it it turned out that there was no deceleration of the upper block and thus no transfer of this kinetic energy could have been accomplished. The problem for Bazant's papers is that his core requirement of a jolt isn't there, so his hypothesis is rendered meaningless as far as it's being able to explain the collapse of the North Tower.



I don't know what you do for a living but from what you say above it appears you are not qualified to comment on these matters, and it is thus incredibly indulgent of you to suggest I seek out leading experts as though I have no expertise of my own and haven't already sought comment from other professionals qualified in this area.

I see no need to continue this discussion as with this reply I think I have laid out everything you would need to come to an informed decision.

You really should look up elastic and inelastic collisions.

 

[boloboffin]

Relevant section from the addendum:

What If the Aircraft Impacted a Higher Floor?

Eq. (1) (Bazant and Zhou 2000) gives the dynamic overload ratio µ₀ = P_dyn/P₀ of the lower part of tower caused by the vertical impact of the upper part after it falls down through the height of the critically heated floor. The value µ₀≈31 results when the impact occurs approximately 20 floors below the top, i.e., around the 90th floor. If the aircraft impacts a higher floor, say, the nth floor, the axial stiffness C of the lower part of tower gets reduced roughly in the ratio 90/n, and the impacting mass m of the upper part of tower gets reduced roughly in the ratio (110-2n)/20 where 110 = total number of floors in the tower. Considering that the critically heated floor (probably the same as the floor impacted by the aircraft) is, for instance, the fourth floor below the top, i.e., 110-n=3, one gets from Eq. (1) a surprisingly large overload, µ₀=29, which would be fatal. But is it not strange that an aircraft impact so close to the top should destroy the whole tower? It is, and the explanation is two-fold:

• First, note that, in Eq. (1), P₀ was defined as the design load capacity for the self-weight only, excluding the additional design axial load P₁ caused in the columns by wind and dynamic loads (P₀=mg). At 20 floors below the top, P₀ may be roughly as large as P₁ , i.e., P₁ /P₀≈1, which means that the total overload ratio, defined as µ=P_dyn /(P₀+P₁), is µ≈15. But on approach to the building top, the cross sections of columns are not reduced in proportion to its weight that they carry but are kept approximately constant, because of various stiffness, dynamic and architectural requirements, as well efficiency of fabrication. So, for n=3, P₁ /P₀≫1. Therefore, µ≪15, and thus a tolerable overload ratio, approximately µ≤2, may well apply in this case, depending on the precise structural dimensions and loads (not available at the moment of writing).

• Second, note that the analysis that led to Eq. (1) implies the hypothesis that the impacting upper part of the tower behaves essentially as a rigid body. This is undoubtedly reasonable if the upper part has the height of 20 stories, in which case the ratio of its horizontal and vertical dimensions is about 52.8/20×3.7≈0.7. But if the upper part had the height of only 3 stories, then this ratio would be about 5. In that case, the upper part would be slender enough to act essentially as a flexible horizontal plate in which different column groups of the upper part could move down separately at different times. Instead of one powerful jolt, this could lead to a series of many small vertical impacts, none of them fatal.​

In theory, it further follows from the last point that, if people could have escaped from the upper part of the tower, the lower part of the tower might have been saved by exploding the upper part or weakening it by some ‘‘smart-structure’’ system so as to make it collapse gradually, as a mass of rubble, instead of impacting the lower part at one instant as an almost rigid body.

 

[Seymour Butz]

However, it doesn't matter as there was no jolt and Bazant's papers are worthless when it comes to explaining the collapse of the North Tower.

He has no hypothesis about the collapse in that paper. It is just an exercise in energy in/out. You're attacking a strawman.

And what about the south tower?

It's undeniably true that it fell crooked.

 

[FineWine]

We don't use the 31g as a basis to calculate the energy losses. The energy losses are a function of the strength of the columns at the top of the lower block and at the bottom of the upper block or on the 97th and 99th floors which are assumed to elastically and plastically deform and then buckle.

Dr. Bazant actually has an error in terms here as Po is the actual design load not the load capacity which would have been at least three times greater due to the factors of safety used in the column design.



There is plenty of valid reason for a massive jolt. How do you think the kinetic energy gets transferred? Why do you think Bazant said there had to be a powerful jolt?



The lack of freefall does not argue against controlled demolition. All it says is that there was some residual resistance remaining. I used an example here the other day where you have a 100 lb. weight supported by 30 columns which can each support 10 lbs. and you then remove 27 of the columns. What happens? The 100 lb. weight fall at 0.7g, not freefall. All that needs to be done is to remove enough columns so that the load above cannot be supported to create the fall.



Please show how the bowing has any import to the continuation of the collapse once it was initiated. It is the continuation of the collapse that the jolt is necessary for, and what the paper addresses.



If you have actually read "The Missing Jolt" paper you would have noticed that we found a significant error in Bazant and Zhou's calculation of the axial stiffness of the columns. They calculate 71 GN/m when it is actually 7.1 GN/m. So they were off by a factor of ten, probably the result of a misplaced decimal point. Using the correct stiffness (C) of 7.1 GN/m in Bazant's equation for overload ratio, gives an 11g Pdyn/Po ratio. In addition to that, I showed you the design load vs. design capacity term error above made by them also, which is somewhat misleading. The columns actually had a capacity of at least 3 times their actual load so now the overload is down to about 367%, not the 3100% Bazant and Zhou show. So much for your credits of mathematical superiority to the Bazant papers over the one I was involved in.

Admittedly, a 367% overload ratio is more than sufficient but how do you transmit it to the lower structure? The answer is that there must be an impulse with it's requisite deceleration to transfer the kinetic energy. If there is no deceleration there is no 367% overload. Bazant knew this and that is why he felt there must have been a very powerful jolt. He just never measured for it. When someone finally measured for it it turned out that there was no deceleration of the upper block and thus no transfer of this kinetic energy could have been accomplished. The problem for Bazant's papers is that his core requirement of a jolt isn't there, so his hypothesis is rendered meaningless as far as it's being able to explain the collapse of the North Tower.



I don't know what you do for a living but from what you say above it appears you are not qualified to comment on these matters, and it is thus incredibly indulgent of you to suggest I seek out leading experts as though I have no expertise of my own and haven't already sought comment from other professionals qualified in this area.

I see no need to continue this discussion as with this reply I think I have laid out everything you would need to come to an informed decision.

What demolition experts have you consulted with?

 

[alienentity]

Relevant section from the addendum:

Thanks for posting this. To me this is much ado bout nothing. The term 'jolt' is just a way of describing the overwhelming impact of the upper block on the lower floor. And after pages and pages of material, the term is used only once....

I see no implication that resistance to this impact should be great enough to be visible as a sharp deceleration.
1) It certainly wasn't symetrical, making this effect less pronounced.
2)Without special hi-speed film you'd probably have no chance at getting the necessary resolution to see this anyway. You could map data points all day long, but that wouldn't help you.
3) There was weakened structure for several floors around the impact zone, which would tend to absorb energy in a more linear fashion.

There are a number of perfectly reasonable, plausible arguments that can be made why you wouldn't see this artifact. And worse, because the Bazant model is not the only one possible, finding fault with it proves absolutely nothing in terms of controlled demolition.

I found it amazingly ironic that Tony discounted the slower-than-freefall collapse as irrelevant to whether there was controlled demolition. How convenient, when he had earlier pointed to the 2.25s near freefall of WTC7 as some kind of proof of CD. That's just ridiculous. You can't have it both ways.
And STeven Jones goes on and on about freefall speed, or the phrase 'very rapidly' to support his crazy thermite hypothesis.
I mean, freefall speed is THE slogan of the 9/11 truth crowd. But it didn't happen with the WTC towers....oh well, it's still proof of controlled demolition anyway.... (groan)

On page 3 of Tony's paper they ask 'Why
not simply check for this deceleration?'
Perhaps the answer is that it is not expected. Tony seems to have confirmed that hypothesis while trying to prove his own.

 

[Heiwa]

Will you explain what stops the falling floors from crashing through each successive floor? Heiwa won't.

There are about 600 bolted floor truss connections/joints to walls per floor. The floor is actually square with a rectangulat hole in it and consist of different sections/panels as per:

The "floor" is inside outer walls and outside the outer core columns indicated in the sketch that just show how much load is carried by outer core columns.

Evidently a floor cannot fall on another floor. For that 600 connections/joints must fail and then the floor must slide down inside the outer walls and the around the core.
What can fall is the upper part C on the lower part A, if you remove all columns in between. Then the lowest floor of C will contact the top floor of A, say floor #98 contacts floor #97 in WTC 1. And when that happens the destruction is arrested.
It has been explained many times.

 

[Heiwa]

Yup, calculations in detail. 'Mechanics of Progressive Collapse: Learning from World Trade Center and Building Demolitions' pp 3 to 10.
Published in Journal of Engineering Mechanics, Vol. 133, No. 3, March 2007.

How many engineering journals have you published your 'bounce' theory in Heiwa? Throw us a link to them.

http://heiwaco.tripod.com/nist3.htm ! The paper is being peer reviewed by ASCE since 3 February 2009.

 

[boloboffin]

Check these out:

http://scott3x.tripod.com/arguments/tony/WTC_bal.html

That's Tony Szamboti's comparison of the WTC 1 velocity and acceleration to the Balzac-Vitry building.

What gets me is that the B-V building does go into deceleration (negative acceleration), but only at the end of the graph. To my admittedly untrained eyes, it seems to me that the B-V building is going through Bazant's two stages. First, a crush-down, in which the upper section does dip in acceleration rates, but stays accelerating overall, and then the crush-up, in which the upper section does indeed experience negative numbers.

And look at those crazy curves in the WTC 1 acceleration graph - up and down and up and down and up and down. And yet Szamboti doesn't see anything peculiar about that simply because the numbers don't go negative! It's cracking me up.

 

[alienentity]

http://heiwaco.tripod.com/nist3.htm ! The paper is being peer reviewed by ASCE since 3 February 2009.

Good luck with the paper. Sincerely.

 

[Heiwa]

To be more precise, it is the kinetic energy from acceleration. A simple clarification that even you can understand.

Now if you care to address the actual topic, be my guest.

As explained many times (topic) the energy applied to the structure A by dropping structure C is transformed into dynamic forces F at contact areas. These forces first compresses the structures A and C and a lot of energy is consumed that way. Then the forces may destroy elements and/or joints in the structures A and C and further energy is lost. When an element is broken no force can be applied on it. When a joint is broken no force F can be transmitted through it. So you have to check where the forces F are then applied. Evidently no floor elements in structure C can suddenly become loose and drop on the top floor of structure A, &c. This is the old pan cake theory that nobody adheres to today.
As explained many times, when a dynamic contact force develops between a strong element (eg column) and weak element (eg floor) the weak element fails first (if any element fail). When damaged elements rub against each other and friction develops a lot of energy is transformed into heat.

This is the reason why structure C cannot destroy structure A (C<1/6A).

Actually very little energy is applied when structure C contacts structure A in the WTC 1 case! It can only compress the structures and produce minor local failures to elements. I have explained it in my papers. See link above.

 

[leftysergeant]

It is now obvious that you are a manipulator. However, the joke is on you mister smarty pants. The jolt Bazant speaks of is in the Addendum to Bazant and Zhou on page 369. It is reference 10 in the Missing Jolt paper. I guess when you are trying to jerk other people around you don't have time to do your own homework on the real issue. I am also sure that where you said you read Bazant's papers probably means browse. Your actual technical knowledge is lacking in that you don't seem to understand that Bazant's overload ratio can NEVER happen and the kinetic energy, no matter how much it is, cannot be transferred, without a significant deceleration. You wouldn't know that though as you probably didn't read the Missing Jolt and browsing won't do for a non-technical person like yourself to fully understand it.

You are also committing an Appeal to Authority fallacy by citing the Journal of Engineering Mechanics when there is a good bit of controversy over Bazant's papers.

I am not nitpicking anything. Bazant's hypothesis does not work at all if there is no massive jolt. He knows that.

Bazant is also wrong about the amount of kinetic energy as opposed to the energy of absorption. It isn't 8.4 times. We calculated that and the collapse would nearly arrest at the first story just with deformation and buckling of the columns above and below the impact. We provide those calculations and Bazant doesn't but some simple minded people just quote Bazant on this. The reality is that when considering other energy losses due to vibration of the building, heat, and sound, the collapse would most probably arrest after a fall of one story or 3.7 meters.

What would arrest it? The perimeter columns? They were not even involved. Look closely. The floors are breaking out. Nothin holdin up ther perimeter columns. How are the perimeter columns going to push back? They are not offering any resistance to compresion because they are not being compressd.

That leaves on the floor slabs as actors in this whole mess.

Bazant may have been wrong on some points, but you are more so.

 

[bill smith]

Relevant section from the addendum:

'In theory, it further follows from the last point that, if people could have escaped from the upper part of the tower, the lower part of the tower might have been saved by exploding the upper part or weakening it by some ‘‘smart-structure’’ system so as to make it collapse gradually, as a mass of rubble, instead of impacting the lower part at one instant as an almost rigid body'.

If you accept- as you must that the top block was of an identical sconstruction with the bottom block you will realse that you cannot say that the top was an 'almost rigid blody' witout accepting that the lower 90% was an even more rigid body being rooted in the ground.

'Impacting the lower part at one instant ' Was that the same instant that the lower part reciprocated in full measure whateever downwards force was applied ?

 

[bill smith]

http://heiwaco.tripod.com/nist3.htm ! The paper is being peer reviewed by ASCE since 3 February 2009.

If they don't publish it Heiwa, will they tell you why giving the reasons ? That would seem to be the fairest because otherwise it could be rejected on political considerations.

 

[KreeL]

Heiwa happens to be ultra-correct here, bananaman. 15% of anything cannot possibly crush 85% of itself on planet earth.

Take a bite of a candy bar. Spit it out. Catch it. Hold it up above the remaining candy bar in your hand and drop it right where you bit it off. What happens? Does the candy bar implode in your hand?

Use common sense. It helps.

 

[ozeco41]

There are about 600 bolted floor truss connections/joints to walls per floor. The floor is actually square with a rectangular hole in it and consist of different sections/panels as per:

which at least confirms that Heiwa is talking about the same building.

It is a pity he has me on ignore - but that means I can explain simple facts of the WTC 9/11 collapses for the benefit of other readers.

So try this bit of Heiwa:

The "floor" is inside outer walls and outside the outer core columns indicated in the sketch that just show how much load is carried by outer core columns.

..good and simple stuff.

Evidently a floor cannot fall on another floor. For that 600 connections/joints must fail

.. yes 600 connections which individually and in sum total are the weakest part of the lower structure in the way of the falling Top Block.

Anyone with common sense knows that in any chain the weakest link fails. How anyone claiming to be an engineer can claim that the weakest link did not fail AND that the strongest link had to fail and therefore needed explosives ...well it is beyond me how they even keep a straight face saying it.

So the weakest link failed.

...facing and then the floor must slide down inside the outer walls and the around the core.

which can be seen from any of thge global collapse videos. David S Chandler even modified one video to make that fact clearer.

Sorry - I will correct that. Davis S Chandler corrected the video to show some claims he makes. It does not support those claims - it is at best ambiguous. The irony is that it does support the true situation. The floors fell, inside the tube, leaving the outer columns standing, unbraced, to fall freely a short time later.

So, once again having got tantalisingly close to the truth Heiwa again takes a quantum leap into fantasy to get off the dangerous track for his fantasy of "no demolition".

What can fall is the upper part C on the lower part A, if you remove all columns in between. Then the lowest floor of C will contact the top floor of A, say floor #98 contacts floor #97 in WTC 1. And when that happens the destruction is arrested.

... no comment needed - another spin of the same rubbish.

...It has been explained many times.

It certainly has. Many times by me. Also by others. And it was so self evident NIST didn't even bother to go there in its original scope.

BUT it has never been explained with any credibility by Heiwa