Debate! What debate?

[Kent1]

"Because thousands of experts and specialists around the world consider this a non-issue."

Oh, really!

Most people apparently don't even KNOW about this.

"A little learning is a dangerous thing;
Drink deep, or taste not the Pierian spring."

Alexander Pope

Frank, have you considered taking it up with the authors of one of the studies regarding Iron-rich spheres. Especially considering the report I read states that they were expected to be present in WTC Dust.
Best Scott

http://216.109.125.130/search/cache...eres+sphere+wtc&d=J_mdLvmdOeY8&icp=1&.intl=us

Considering the high temperatures reached during the destruction of
the WTC, the following three types of combustion products would be
expected to be present in WTC Dust. These products are:
• Vesicular carbonaceous particles primarily from plastics
• Iron-rich spheres from iron-bearing building components or contentsDamage Assessment
• High temperature aluminosilicate from building materials

 

[e^n]

"Because thousands of experts and specialists around the world consider this a non-issue."

Oh, really!

Most people apparently don't even KNOW about this.

We're talking about the World Trade Centres here, I'm reasonably certain that every structural engineer in the world is aware of the collapse, and I find it hard to believe that if many saw a significant disparity with what they expected that they would not bring it up. So far a minimal number of qualified people have expressed issues.

Please also answer my above post, as while not a scientist I believe I am intelligent enough to make observations on the individual likelyhood of sources of spherical micron sized iron particles.

 

[Gravy]

BELZ, GRAVY, ENIGMA, PARDALIS:

Since all of you appear to believe/support the NIST Report, I am interested in your qualifications and/or experience in the fields of ENGINEERING, PHYSICS, CHEMISTRY, or MATERIALS SCIENCE.

If you do indeed have a background in chemistry, metallurgy or materials science, could you please tell me: what is your scientific understanding of the significance of micron sized iron spheres in the WTC dust.

But if you lack credentials or hands-on experience in any of the areas of scientific enquiry noted above, I wonder why you consider your OPINIONS on the collapse of WTC 1 & 2 of interest or value to anyone......

R. MACKEY:

I am still thinking about those lateral forces.....

I'm an English major who is known for taking long walks. In this thread I asked you how you distinguished your "micron sized iron spheres," which you say can only be generated by high heat, from the particles produced by the ironworkers' torches at ground zero. I also asked you how your measurements of this iron compare to measurements made prior to 9/11, if any.

Your reply?

 

[metamars]

Originally posted by metamars


Calladine and English are meaningless in this instance, as they test they preformed was on steel plate, do to the geometry of the steel in the world trade center and its ability to form fulcrums in the structure and tear the weld joints Calladine and English do not apply.

Intuitively, a steel plate is so many steels rods (square-ish cross section), sitting right next to each other. I expect the relationship to be strictly linear (wrt the weight of the apparatus), or failing that, calling for truly minor corrections. Presumably, somebody could show this rigorously.

Even when dealing with (non-hollow) square rods, you are still not mimicking the actual structure of the WTC columns, exactly. And geometry does matter, as the CE paper itself, makes clear.

When you write

Exactly my point they are not steel flat plate, I work with steel all the time I have to take this stuff into consideration. The shape of the material drastically effects the way it is effected by stress. Before you can use Calladine and English, to correct Bazant, you must first correct Calladine and English for the shape of the materials in question. I believe that Bazant wrote a paper or an editorial on it some time back with the calculations to correct mechanical stress analysis for different shapes. IN a journal of fracture mechanics , though I am not sure when it was published or what volume it is in. I will try to find it though.

you are actually re-iterating a suggestion I made elsewhere, viz., that the Calladine and English apparatus and their Type II structure be modified to be more relevant to the WTC.

However, your claim is that the CE results and the WTC structure are so different that no useful corrections to BZ and Greening can occur strikes me as incredible. However, even that claim, were it to be true, would be well served with a mathematical demonstration.

NO it most certianly has not it is just that no one else has come up with a better model.

In light of CE, this statement (if true) strikes me as a crying shame. Happily, it's a situation that I believe is easily rectifiable.

I agree there are minor corrections to Bazant but not from Calladine and English, as they are not testing in any comparable way the structure or the integrity of hollow steel columns that work on in a different manor that flat plate steel.

See above.

Then you do not understand Cherepnov's fracture wave paper. Columns acquire their strength from leverage, the ability to resist Buckling flat plate is easy to bend but Columns are not. Columns actually absorb more impact energy than flat plate which will dissipate it though oscillations faster. That is why Calladine and English are meaningless you would first have to correct Calladine and English for hollow square Columns before it would have relevancy.

? I suppose, then, by leverage you mean second moment of inertia?

Since "columns absorb more impact energy than flat plate", perhaps somebody can figure out how much?, and furthermore, what is the relationship wrt speed of impact? At the end of the day, I'd like to see a quantitative answer, anyway. Also, I believe (though I'm not sure) that Calladine and English was a seminal paper. It's almost natural to expect that somebody has extended their work using I-beams and square and box columns.

I'm skeptical that you know this to be the case for dynamic impacts. I suspect that you are assuming that energy figures determined under quasi-static compression has the same relationship in the dynamic case of impacts.

In any event, if a tall thin piece of metal absorbs X amount of energy in a given impact scenario, and buckles but does not break, it has demonstrated the ability to absorb all of the kinetic energy that impacted upon it.

If it were true that a tall thin piece of metal, of the same weight and height but with with a hollow box cross section was capable of absorbing even more energy, I think that would be irrelevant, as the non-hollow case would constitute an upper bound of energy that was actually needed to absorb the blow. Remember, the bottom of the apparatus is fixed. There will be some losses of energy through the bottom, but I believe they're negligible.

Think of the CE apparatus as Las Vegas. What happens in Las Vegas, stays in Las Vegas!

BTW, one of the reasons I've called for expanded CE experiments, is because even in CE, the bottom of the apparatus is essentially fixed. This matches the (unstated) BZ assumption that the topmost floor is sitting atop a perfectly rigid base. (Until the collapse front descends to the next floor.)

In real life, though, the columns of any given floor are likely to be sitting atop identical, or very similar, other columns. There is no particularly good reason to presume that the bottoms of the columns of the impacted floor must "sit and wait", so to speak, while their respective columns sections are getting crushed.

In short, I expect the most reasonable elaborations of CE to the WTC scenario to favor survival, in an axial strike.

But, one thing at a time.

 

[R.Mackey]

... However, at the end of the day, one would like to see a complete treatment, incorporating whatever objections one might have to the Bazant Zhou paper. If I were able to do that with the Calladine and English paper, I would have done so, already. Instead, I am calling on others, better equipped than myself, to do so.

...Thus, my comment should be understood as an expression of personal mistrust more than a necessary logical inference.

...Even if the Ross paper is "full of holes", I specifically referred to his conclusion as what I expected to remain unchanged, if his paper was refined or corrected as per Calladine and English.

...To tell you the truth, it's been so long since I took my degree, I'm not even sure whether or not I could have fully digested the CE paper, and then figured out it's implications for BZ and Greening, or not, at the time of my graduation.

This non-argument of yours really isn't helping. I haven't read Calladine and English, and you don't have what it takes to apply it. There is no reason at this stage to believe it makes any difference.

If I get a chance, I will read it, and if it looks relevant to me, I will think about it. I don't expect it to make a difference.

And CrazyChainsaw's objections are valid. Plates and columns are not the same, welds are significant, the apparatus may be only a vertical model and poorly suited to the early collapse dynamics. I strongly suspect there are other scaling laws that apply, since scaling is a tricky thing to do. But like I said, since neither of us has the knowledge to do anything with it, such argument is fruitless.

However, the argument is half-baked not only in a discussion of how legitimate the phrase "near free fall is", but even moreso in terms of this thread. Without calculating, from first principles, how much energy you need to collapse the structures, of what significance is this calculation? Let us say that the collapse takes 15 seconds (BTW, I personally put most stock in Hoffman's estimates, which IIRC are in the 12 - 14 second range or thereabouts; however, I haven't paid much attention to this particular debate in a long time) From your calculations, we conclude that this requires the structure to absorb the energy equivalent of 99.1 tons of TNT. However, if our calculation from first principles shows that the energy equivalent of 100 tons of TNT are required to collapse the structure, and not a joule less, then you have an indication that something was done to the building to lower the threshold required for complete collapse.

You've missed the point of my simple energy calculation. (I can do "heavy lifting," but this simple argument gets the point across more elegantly.)

The point is that the collapse time and destruction energy have a hyperbolic relationship. For small values of collapse time, say between 10 and 17 seconds, the collapse time is a strong function of destruction energy, but it behaves about the same. However, for long values of collapse time, the collapse time becomes extremely sensitive to small changes in the destruction energy. For example, the difference between 10 and 11 seconds is 24 tons TNT, but 30 seconds and 40 seconds is a difference of only 15 tons TNT.

What this means is that, if the collapse is total, it's probably fast. A slow collapse means a very delicate, sensitive balance between strength and energy, one that is unlikely to occur by accident. It would also be greatly affected by factors like mass lost over the side.

But both collapses happened in ~ 12 to 15 seconds, in which case such factors are a minor correction, and unlikely to change whether or not it did fall. The rapid collapse demonstrates -- as a revision of Ross's calculations confirm -- that there was a significant energy surplus during the collapse.

 

[Belz...]

I'm confused. Was Apollo serious about this thread, or was it just an exercise in irony ?

 

[Belz...]

"Because thousands of experts and specialists around the world consider this a non-issue."

Oh, really!

Most people apparently don't even KNOW about this.

I'm reasonably certain that every structural engineer in the world is aware that the World Trade Center no longer exists.

 

[Kent1]

I'm reasonably certain that every structural engineer in the world is aware that the World Trade Center no longer exists.

He's talking about the Iron-rich spheres specifically.

 

[David Wong]

"Because thousands of experts and specialists around the world consider this a non-issue."

Oh, really!

Most people apparently don't even KNOW about this.

"A little learning is a dangerous thing;
Drink deep, or taste not the Pierian spring."

Alexander Pope

No real scientist talks that way.

Either this isn't Greening, or Greening's cheese has slid off his cracker.

 

[HyJinX]

I thought Apollo20 was Dr. Greening. Was I wrong?

 

[Belz...]

He's talking about the Iron-rich spheres specifically.

Well, I wasn't.

 

[metamars]

This non-argument of yours really isn't helping. I haven't read Calladine and English, and you don't have what it takes to apply it. There is no reason at this stage to believe it makes any difference.

If I get a chance, I will read it, and if it looks relevant to me, I will think about it. I don't expect it to make a difference.

Your muted interest is duly noted. Frankly, while I don't know a lot about the JREF forum, I can't say that I'm terribly optimistic about finding anybody who is a 'regular', and who is qualified, taking an objective look (which implies reading the paper). But hey, it's worth a shot.

One individual I got the paper to is structural engineer Korol, who pronounced it "very well done", though he hasn't commented regarding it's applicability to BZ. Korol, BTW, doesn't believe in a "natural" collapse. I doubt NIST will be offering him a job, anytime soon.

JREF is only one corner of the world, and if nobody here who is qualified is at all is interested, well, I'll have to keep looking until I find somebody.

And CrazyChainsaw's objections are valid. Plates and columns are not the same, welds are significant, the apparatus may be only a vertical model and poorly suited to the early collapse dynamics.

It's odd that similar concerns do not inhibit the proponent of BZ from singing it's glories. After all, dynamic and quasi-static are not the same, welds are significant, and the 1-dimensionality of the BZ is doubtless poorly suited to modeling lateral cross connections, which are relevant to the building's ability to resist collapse and play into considerations of whether a vertical collapse is more likely than a toppling over collapse.

I strongly suspect there are other scaling laws that apply, since scaling is a tricky thing to do. But like I said, since neither of us has the knowledge to do anything with it, such argument is fruitless.

It certainly would make more sense to make this claim after technically competent individuals make a go of it. I suppose one could say that some differences in our viewpoints include: 1) I've actually read the paper (even if not understanding it totally) and 2) I am eager to see technically competent individuals reconcile it with BZ, Greening, and Ross.

You've missed the point of my simple energy calculation. (I can do "heavy lifting," but this simple argument gets the point across more elegantly.)

The point is that the collapse time and destruction energy have a hyperbolic relationship. For small values of collapse time, say between 10 and 17 seconds, the collapse time is a strong function of destruction energy, but it behaves about the same. However, for long values of collapse time, the collapse time becomes extremely sensitive to small changes in the destruction energy. For example, the difference between 10 and 11 seconds is 24 tons TNT, but 30 seconds and 40 seconds is a difference of only 15 tons TNT.

What this means is that, if the collapse is total, it's probably fast. A slow collapse means a very delicate, sensitive balance between strength and energy, one that is unlikely to occur by accident. It would also be greatly affected by factors like mass lost over the side.

But both collapses happened in ~ 12 to 15 seconds, in which case such factors are a minor correction, and unlikely to change whether or not it did fall. The rapid collapse demonstrates -- as a revision of Ross's calculations confirm -- that there was a significant energy surplus during the collapse.

In light of my previous comments, insights into whether or not your calculation is disfavorable to the idea of a "delicately balanced" collapse, "unlikely to occur by accident" is a red herring. It's an interesting insight, but only one aspect of the collapse, and of no importance should there be insufficient gravitational potential energy available to collapse the structure in the observed time.

Should your calculations of "energy surplus" be valid, that would be a much stronger argument for non-CD. However, as you admit, you have not read CE. Thus, I strongly doubt your calculations have any good accounting of the dynamic effects studied by CE.

Probably, they have no accounting of inertial effects ala CE, whatsoever. Am I correct in this supposition?

 

[Crazy Chainsaw]

BELZ, GRAVY, ENIGMA, PARDALIS:

Since all of you appear to believe/support the NIST Report, I am interested in your qualifications and/or experience in the fields of ENGINEERING, PHYSICS, CHEMISTRY, or MATERIALS SCIENCE.

If you do indeed have a background in chemistry, metallurgy or materials science, could you please tell me: what is your scientific understanding of the significance of micron sized iron spheres in the WTC dust.

But if you lack credentials or hands-on experience in any of the areas of scientific enquiry noted above, I wonder why you consider your OPINIONS on the collapse of WTC 1 & 2 of interest or value to anyone......

R. MACKEY:

I am still thinking about those lateral forces.....

You know my qualifications Frank, I can only assume by the evidence in the samples that a very high temperature reaction involving steel resulted in the buildings as that would explain the formation of the spheres, Whether that is an Aluminum Oxidizing reaction, that heated the steel to high temperatures or pyrophoric iron, or even the carbon boil reaction, I do not know I have been looking into all possibilities though.
I would be very Happy if some one could point out some reaction that I missed.
To my Nist is simply a reference the best work so far, but certainly it could be improved up on by further independent investigation though the scientific method.
I have discounted an Iron oxidizing reaction because you used the term Iron spheres, not Iron Oxide spheres.
What ever your referring to Frank I know that there is Scientific grounds for your Theory.

 

[Mince]

It all gets pretty much routine because the JREFers always use one or more of the following modes of attack:

(i) NIST has covered all the bases – you need to refute NIST to win an argument here.
(ii) Taunt the CTist with “where’s your evidence?”
(iii) Question the CTist’s credentials – “Are you a scientist?”; “Are you an engineer?”
(iv) Ask the CTist why there are no peer-reviewed journal articles refuting NIST.
(v) Ask the CTist if they are going to submit an article to a peer-reviewed journal

Good point. It's kind of like when I'm going in for surgery. I don't want to confirm the credentials of the surgeon. That might upset him. He is going to operate on me, after all.

 

[A W Smith]

What I don't understand from reading this thread is. Why wait till April to polish off that bottle of scotch from Christmas?

 

[Anti-sophist]

BELZ, GRAVY, ENIGMA, PARDALIS:

Since all of you appear to believe/support the NIST Report, I am interested in your qualifications and/or experience in the fields of ENGINEERING, PHYSICS, CHEMISTRY, or MATERIALS SCIENCE.

But if you lack credentials or hands-on experience in any of the areas of scientific enquiry noted above, I wonder why you consider your OPINIONS on the collapse of WTC 1 & 2 of interest or value to anyone......

It all gets pretty much routine because the JREFers always use one or more of the following modes of attack:

(i) NIST has covered all the bases – you need to refute NIST to win an argument here.
(ii) Taunt the CTist with “where’s your evidence?”
(iii) Question the CTist’s credentials – “Are you a scientist?”; “Are you an engineer?”
(iv) Ask the CTist why there are no peer-reviewed journal articles refuting NIST.
(v) Ask the CTist if they are going to submit an article to a peer-reviewed journal.

How am I to interpret these two posts, taken together?

 

[Apollo20]

Gravy:

Degree in English? Oh, I didn’t realize that. I enjoy discussing English literature. It's all about archetypes isn't it? - my wife has an English degree. But I was assuming you had some technical training and/or experience…...

E^N:

Spherical iron particles are direct physical evidence that the iron within the particle was molten at the time the particle formed.

Each of the references below specifically mention the detection of iron spherules in WTC dust samples (and in most cases also provide electron micrographs of the particles in question). Reference 1 includes two such micrographs labeled IRON-03-IMAGE and IRON-04-IMAGE. Reference 2 discusses which WTC particles could best be used as signatures of WTC dust; iron spheres were considered and rejected only because they were not found in ALL indoor dust samples. In reference 3 we read on page 17: “Various metals (most notably iron and lead) were melted during the WTC event, producing spherical metallic particles.” And finally in reference 4 we find a micrograph of a spherical iron particle and the comment that WTC dust contains evidence for “heat effected particles, including spherical particles.”

1. H. A. Lowers et al. “Particle Atlas of World Trade Center Dust.” USGS Open-File Report 2005-1165, (2005)

2. Various authors: “U.S. EPA Response to the Peer Review of the U.S. Environmental Protection Agency’s Final Report on the World Trade Center Dust Screening Study.” Page 28, (December 2006)

3. R. J. Lee et al. “Damage Assessment 130 Liberty Street Property: WTC Dust Signature Report on Composition and Morphology.” Issued December 2003.

4. S. R. Badger et al. “World Trade Center Particulate Contamination Signature Based on Dust Composition and Morphology.” Microscopy and Microanalysis 10 (Supplement 2), 948, (2004).

The formation of spherical iron particles has been well documented and researched for steel making processes, (See for example: Steel Research 64, 23, (1993) and Steel Research 72, 324 (2001)). Iron spheres in the 30 micron to 1 micron range are typically seen in the dust-laden off-gases produced by molten steel and are believed to be formed by the ejection of metal droplets when the liquid metal degasses.

NIST, in its fire simulations, tried very hard to get steel (>95 % iron) to temperatures above 1000 deg C but failed! This is not surprising because NIST was using kerosene or hydrocarbon/cellulosic-based fuels. NIST WANTED high temperatures to support the idea that the structural steel was weakened by heating effects.

Nevertheless, some steel appears to have melted in the WTC prior to the collapse of the buildings. Interestingly some of the NISTIANs posting on this site appear to be bothered by that, preferring to deny the physical evidence for molten iron.....

Oh, the IRONy!

About the suggestion that the iron spherules came from cutting operations:

1. It does NOT account for the high concentrations of airborne ZINC and the detection of zinc spherical particles in WTC dust - see the paper by E. M. Fireman entitled “Induced Sputum in Firefighters Exposed to WTC Dust” published in Environmental Health Perspectives 112(15), 1564, (2004).

2. Steel cutting operations (according to OSHA data) usually generate "fume" concentrations less than 1 mg/m^3 in the vicinity of a typical torch-cutting operation and less than 10 g of iron fume is released per operation. If there were 10,000 cutting operations at ground zero during site clean-up, that is a total of only 100 kg of iron fume. I have previously estimated that over 200 tonnes of iron spherules were produced during the collapse of WTC 1 & 2.

3. The iron spherules were ubiquitous in the WTC dust. Thus they were easy to find in a total of say 50,000 tonnes of dust. Try finding 100 kg of something in 50,000 tonnes of material.

4. Cutting operations were carried out on average within 5 meters of the ground. Iron particles in the size range we are considering (~ 10 microns) have settling velocities such that the particles would all settle-out within 200 meters of GZ given the wind speeds recorded in Lower Manhattan in September 2001.

5. The USGS samples were collected WITHIN ONE WEEK of 9/11 well BEFORE there had been major cutting operations and some USGS samples were collected up to 1 km from GZ. Many of the R.J. Lee Group's samples were collected high up in 130 Liberty Street, a location that would be inaccessible to > 10 micron cutting fume particles.

Chainsaw:

Thanks for your interesting comments

 

[Mince]

How am I to interpret these two posts, taken together?

He's obviously putting his (flawed) philosophy of the first post into action in the second post. Apparently he thinks an MA in English is aptly qualified to sufficiently discuss Thermodynamics, and that an MS in Quantum Physics is aptly qualified to sufficiently discuss the Romanticist structure and stylings of Keats, merely by having a degree. Why have distinct educational disciplines if this is the case? You can to school for 55 years and earn an ME (Master's of Everything). Then you can use your knowledge of everything to continuously and frivolously accuse people of mass murder. How whimsically delightful.

 

[Apollo20]

Anti-Sophist:

"How am I to interpret these two posts, taken together?"

That's easy: "WHAT'S GOOD FOR THE GOOSE IS GOOD FOR THE GANDER"

 

[Crazy Chainsaw]

oridginaly posted by metamars

Intuitively, a steel plate is so many steels rods (square-ish cross section), sitting right next to each other. I expect the relationship to be strictly linear (wrt the weight of the apparatus), or failing that, calling for truly minor corrections. Presumably, somebody could show this rigorously.

I believe somebody should Show it rigorously, but no a steel plate is not so may steel rods, as the crystalline nature of steel is what gives it strength just attaching the rods together increased the strength by the added molecular bonding.
So a steel plate would be stronger than the steel rods, and the rods because steel is so good at sonic shedding of energy, would dissipate more energy as sound vibrations than the steel plate.
Crystalline metalics are very complex structures, and very dynamic in themselves.
The steel rods might be a simplistic model for easy understanding though but they might also be to simplistic.

Even when dealing with (non-hollow) square rods, you are still not mimicking the actual structure of the WTC columns, exactly. And geometry does matter, as the CE paper itself, makes clear.

Agreed,

When you write

you are actually re-iterating a suggestion I made elsewhere, viz., that the Calladine and English apparatus and their Type II structure be modified to be more relevant to the WTC.

It would take a lot of work but I believe it Could be done in time however it would as I said take a lot of work the variables from going from steel plate to the world trade center are gigantic.

However, your claim is that the CE results and the WTC structure are so different that no useful corrections to BZ and Greening can occur strikes me as incredible. However, even that claim, were it to be true, would be well served with a mathematical demonstration.

I was referring to the paper without modification. To account for the Geometrical differences. That is because the energy dissipation rates of flat steel plates and Hollow square Columns, and steel I beams are so dissimilar do to compressive and tension forces that both have to be accounted for. ON a flat plate tension plays a larger role than compression, on a beam to buckle one side you have to compress one side.

In light of CE, this statement (if true) strikes me as a crying shame. Happily, it's a situation that I believe is easily rectifiable.

I feel that It could given the resources and the time.

? I suppose, then, by leverage you mean second moment of inertia?

Standing columns work in both tension and compression, in the world trade center one side has to compress while one side has to fail do to tension. With out the formation of a hinge joint the top block would not even tilt.

Since "columns absorb more impact energy than flat plate", perhaps somebody can figure out how much?, and furthermore, what is the relationship wrt speed of impact? At the end of the day, I'd like to see a quantitative answer, anyway. Also, I believe (though I'm not sure) that Calladine and English was a seminal paper. It's almost natural to expect that somebody has extended their work using I-beams and square and box columns.

I believe the paper has been extended!

Speed of impact imparts more Momentum into the Column the higher the speed the more momentum the more energy the beam has to absorb. Also the more off center the impact the less energy it takes to form a facture wave.

I'm skeptical that you know this to be the case for dynamic impacts. I suspect that you are assuming that energy figures determined under quasi-static compression has the same relationship in the dynamic case of impacts.

No I am looking at both Dynamic Impacts and Quasi-static compression.

In any event, if a tall thin piece of metal absorbs X amount of energy in a given impact scenario, and buckles but does not break, it has demonstrated the ability to absorb all of the kinetic energy that impacted upon it.

Both absorbtion and dissapation of energy have to be taken into acount since it is dissapation or rebounding energy that creates Shock and fracture waves.

If it were true that a tall thin piece of metal, of the same weight and height but with with a hollow box cross section was capable of absorbing even more energy, I think that would be irrelevant, as the non-hollow case would constitute an upper bound of energy that was actually needed to absorb the blow. Remember, the bottom of the apparatus is fixed. There will be some losses of energy through the bottom, but I believe they're negligible.

NO if the bottom of the apparatus is fixed, and can not dissipate energy than that energy rebounds though the structure forming shock waves, Fracture waves, even supersonic sound waves. That sound like an explosion, or Lightning Think of a tuning fork the dissipation rates of the materials must be similar for the energy not to rebound back upward from a rigid foundation. It is a simple matter of reflection of the original energy back along the columns, only at a slightly lower frequency.

Think of the CE apparatus as Las Vegas. What happens in Las Vegas, stays in Las Vegas!

BTW, one of the reasons I've called for expanded CE experiments, is because even in CE, the bottom of the apparatus is essentially fixed. This matches the (unstated) BZ assumption that the topmost floor is sitting atop a perfectly rigid base. (Until the collapse front descends to the next floor.)

In real life, though, the columns of any given floor are likely to be sitting atop identical, or very similar, other columns. There is no particularly good reason to presume that the bottoms of the columns of the impacted floor must "sit and wait", so to speak, while their respective columns sections are getting crushed.

That depends on how plastic the columns are when the collapse occurs, if suficently plastic, the columns do not absorb as much energy though impacts. If rigid the energy is absorbed more and more effects occur within the columns.
In fact fracture wave formation does not occur much in highly plastic structures because the speed at which the fracture wave moves though the material is reduced simular to what happens with sound waves and heating.

In short, I expect the most reasonable elaborations of CE to the WTC scenario to favor survival, in an axial strike.

I have to disagree with you there, respectfully of course the data does not point to prevention of weld failure which was the major cause of the collapse.

But, one thing at a time.

Have you looked at what DBB did on physorg, in reguard to fracture waves?

PS. IT was some of your very posts that got me looking into this fascinating subject.