OOS Collapse Propagation Model

[Major_Tom]

Limit case.

The way I see it, there are four energy terms here. Let's call them E1, E2, E3 and E4.

E1 is the energy available to sustain collapse to ground level.
E2 is the energy required to sustain collapse in the most optimistic scenario.
E3 is the energy required to sustain collapse in the actual event.
E4 is the energy to sustain collapse in the ROOSD scenario.

Bazant and Zhou states that E1>E2. By definition E2>=E3, therefore E1>E3. Bazant seems to have fallen a little in love with his own model and over-applied it in later work, but that central conclusion of B&Z is the one that 9/11 truthers find most irksome. The main argument has therefore been whether E1>E2 is a true statement, because truthers can't seem to figure out that, even if it were true, E1<E2 does not imply E1<E3; Tony Szamboti among others is a master of this fallacy. However, Bazant is defending the claim that E1>E2, because if that is established then no further analysis is necessary to prove that the collapse was self-sustaining. And that, in a nutshell, is the limit case.

Major Tom, meanwhile, is up in arms because Bazant has not addressed the question of whether E4=E3, and claims that this demonstrates intellectual dishonesty on the part of Bazant. Since the very existence of the term E4 is never more than vaguely implied in Bazant's work and is not necessary to its most important conclusion, this seems an untenable claim by MT.

(Menawhile, CC is implying that E3>E4 from the collapse time, which is a most interesting result if valid; it strongly suggests some other mechanism than ROOSD.)

Dave

You have a PhD in physics.

You made one somewhat correct statement with regard to anything I wrote:

Bazant seems to have fallen a little in love with his own model and over-applied it in later work...

Kind of, but he didn't over-apply it in later work. He developed the crush down (BV equation 12) and crush up (BV equation 17) in 2007. It had nothing to do with his 2002 argument.

In 2008, he went way over the top in BL (closure to BV) applying the 2007 model quite literally to the WTC towers. The evidence for this is overwhelming in the direct quotes I reproduced from the paper linked here.



David Benson, co-author of BLGB (2008), in an exchange with me, also applied the concept of crush down - crush up quite literally to the WTC towers. The evidence for this is overwhelming in his direct quotes that I have reproduced from our exchange linked here.


>>>>>>>>>>>>>


Dave, from your quote above it certainly appears that you have never read either BV (2007) or BL (2008), is that correct?



Please answer honestly, did you ever read either of these papers?

 

[Major_Tom]

You seem to be arguing that B&V is an argument to validate some prediction about WTC when, as I read it, its just an argument about the mean energy dissipation per story, and (to use their language) therefore "the energy absorption capacity of various structures." This is meant to generalize across many stuctures.

Part 1: Mechanics of Progressive Collapse: Learning from World Trade Center and Building Demolitions

Zdenek P. Bazant and Mathieu Verdure (BV), published in 2007, the paper linked here


Part 2: Closure to 'Mechanics of Progressive Collapse: Learning from World Trade
Center and Building Demolitions' by Zdenek P. Bažant and Mathieu Verdure

Zdenek P. Bazant and Jia-Liang Le (BL), published in 2007,

March 2007, Vol. 133, No. 3, pp. 308–319.
DOI: 10.1061/(ASCE)0733-9399(2007)133:3(308)
The paper is linked here



You have to read the closure to the paper, too. It is all about the WTC towers. The evidence for this is overwhelming.

 

[Major_Tom]

Again, I am not myself interested in discussing BV or BL - in fact, I haven't read them.

Thanks for admitting that. There is no logical reason to express strong views of any kind over a paper you have not read.

I suspect many people expressing strong views over a period of 5 years, from the very first page of this thread, have never read the papers in question.

The very few people who have read BV (2007) have never read the closure to BV which is BL (2008). Yet they have been expressing very strong views on what Bazant meant within the closure paper for over 5 years.

R Mackey had clearly never read the paper, and didn't even know it existed.


I have seen no evidence that Dave Rogers has read BV or the closure to BV, which is BL.


Newtons Bit had read BV, but there is no evidence within any of his posts that he had read BL.

 

[Crazy Chainsaw]

Thanks for admitting that. There is no logical reason to express strong views of any kind over a paper you have not read.

I suspect many people expressing strong views over a period of 5 years, from the very first page of this thread, have never read the papers in question.

The very few people who have read BV (2007) have never read the closure to BV which is BL (2008). Yet they have been expressing very strong views on what Bazant meant within the closure paper for over 5 years.

R Mackey had clearly never read the paper, and didn't even know it existed.


I have seen no evidence that Dave Rogers has read BV or the closure to BV, which is BL.


Newtons Bit had read BV, but there is no evidence within any of his posts that he had read BL.

Yes Major Tom we all know, if you check my posting history on all the forums you will note I quit posting when it was clear, that David Benson, was going to use the crush down, crush up model which I knew was wrong before BLGB was published.

Yet you subscribe your meme falsely to me!

By now it is old news.

Do you even have a clue what would have shielded the core and allowed the spire to form?

 

[JSanderO]

Do you even have a clue what would have shielded the core and allowed the spire to form?

The core was not "shielded" from any collapse. A similar vertical floor collapse took place inside the core. In fact the core floor section MIGHT have preceded the ROOSD... but the whole thing went runaway pretty quickly.

When people refer to "core led" what do you suppose the mean? I take it to mean that the beams, girders and columns were getting pushed out of what by HEAT and in the process the floor slabs which were composite were probably fracturing and dropping in local "chunks" which at some point grew to be the threshold destruction mass of the inside the core "floor collapse" which... you realized destroyed all those stone cold slabs below the plane strike zone.

I haven't read the Mr B papers and I have no intention to do so. They don't as far as I can tell from reading other comments... actually try to explain what initiated the collapse... the only area of interest to me.

The visual drop we SEE is the facade and the antenna. Can you see what was happening to the core "steel structure"?

What you eventually DO see is the spire which had col 501 standing to floor 72 or so. Dat's it...

 

[Crazy Chainsaw]

The core was not "shielded" from any collapse. A similar vertical floor collapse took place inside the core. In fact the core floor section MIGHT have preceded the ROOSD... but the whole thing went runaway pretty quickly.

When people refer to "core led" what do you suppose the mean? I take it to mean that the beams, girders and columns were getting pushed out of what by HEAT and in the process the floor slabs which were composite were probably fracturing and dropping in local "chunks" which at some point grew to be the threshold destruction mass of the inside the core "floor collapse" which... you realized destroyed all those stone cold slabs below the plane strike zone.

The visual drop we SEE is the facade and the antenna. Can you see what was happening to the core "steel structure"?

What you eventually DO see is the spire which had col 501 standing to floor 72 or so. Dat's it...

I already know that, but what your not getting is I knew about that in 2008, the falling mass should have caused failure, even if the columns themselves by passed.
Ossilations similar to the sound reflections, Rodriguez Heard in the basement helped shield some core elements.
Some sections of the core would vibrate rapidly when rebounding from beam on beam strike.

 

[Myriad]

Those assertions are true. Most importantly you confirm that Myriad rested on BV (specifically BV at this stage) I agree that also.

Really? Pray tell, what did I rest on BV, on what occasion?

This should be interesting...

 

[JSanderO]

I already know that, but what your not getting is I knew about that in 2008, the falling mass should have caused failure, even if the columns themselves by passed.
Ossilations similar to the sound reflections, Rodriguez Heard in the basement helped shield some core elements.
Some sections of the core would vibrate rapidly when rebounding from beam on beam strike.

I have no way to tell a thing about vibrations or whether they oscillated enough to induce more damage. Beyond my pay grade.

 

[Crazy Chainsaw]

Would you like for me to explain how vibrations in the upper in pinned columns of the upper block
Ejected mass from the core to the outer floors, as the buildings decentigrated?

 

[Bravin Neff]

You have to read the closure to the paper, too. It is all about the WTC towers largely about their model and provides answers to questions from their interlocutors in context. The evidence for this is overwhelming.

FIFY

I have read the paper. I thought pgimeno's comments were basically right:

ahttp://www.internationalskeptics.com/forums/showthread.php?postid=10891238#post10891238

What did you think?

By the way, I sympathize if you, like Gourley, thought B&V was literally a model of the WTC collapses and found it disconcerting.

 

[Crazy Chainsaw]

I have no way to tell a thing about vibrations or whether they oscillated enough to induce more damage. Beyond my pay grade.

I did a test with a model steel core, 30ft by 40ft welded frame, the ossilations as the two cores dropped the one lower 40ft section pinned, the other 30 ft section unpinned.

Because sound travels at over 5000 meters per second in steel, the vibrations Ossilations were intense even for such a small model.

 

[ozeco41]

...Let me summarize in one sentence: B&V is not a model of WTC per se, it is a model about progressive collapse based on three parameters, of which WTC is but one of an infinite number of potential examples..

not in dispute - now take the next steps. Is WTC a valid example? Which is one of the points I keep repeating and everyone keeps ignoring. The dispute will keep circling if:
A) I don't lose patience; OR
B) People keep repeating the same points I have asserted and explained many times and pretending that they are addressing issues of disagreement whilst they refuse to move to those next steps.

I would prefer to explain these matters from zero base HOWEVER this is my position on the currently relevant aspects of BV. (Preliminary position remember I am still playing on the topic chosen by my opponents and I have not at this stage posted a full and rigorous critique of BV.)

The BV base premise is a 1D approximation which also calls up "crush down/crush up" which is itself a derivative of 1D. Specifically again it relies on column crushing energetics.

Who is game to state their position on that assertion? Whether for or against - in the latter case giving reasons?

Meanwhile I have several times identified TWO valid points where those opposing me can counter my arguments:
1) Prove that BV does NOT model on 1D, column crushing energetics and CD/CU: OR
2) Prove that even with those three in place it is a valid approximation.

Short of writing a road map what more do members want?

And I've actually published a road map AND invited members to use mine OR draw their own. No takers.

.ETA: When I say "you seem to be arguing that B&V is an argument to validate some prediction about WTC," I mean some prediction about the way it collapsed, or the speed it collapsed, or something like that. I don't see how its any of those things.

Try that point vice versa.

And I'm probably going to discontinue this discussion. The entrenched determination to miss the points hasn't changed in four years.

Including the preference of my opponents to focus on later papers whilst they ALL refuse to respond to my arguments starting from zero base.

So the exercise is pointless. I mean my attempts at reasoned explaining - not your efforts.

I've been accused of being stubborn. You bet I'm stubborn on the basic principles of discussion. someone makes a claim - in this case me. Some one then agrees or disagrees and posts EITHER:

(i) Reasoned argument rebutting my ARGUMENT (NOT merely unsupported bare assertions stating a counter-claim) OR
(ii) An alternate reasoned hypothesis which is at least as comprehensive as mine.

Neither of those is happening and anyone who knows me will expect me to reject the implicit reversed burden of disproof from persons who neither address my arguments nor present sufficiently comprehensive reasoning of their own.

And I have posted all manner of explanations raging from simple to full complexity. And at levels of language and concept ranging from high school student up to post graduate managers.

There is no dialogue on the issues of concern and I'm not the one avoiding it.

 

[JSanderO]

Would you like for me to explain how vibrations in the upper in pinned columns of the upper block
Ejected mass from the core to the outer floors, as the buildings decentigrated?

Go for it!

 

[Crazy Chainsaw]

Go for it!

As the beams and girders are impacted, this forces inward tension on the core columns, when the welds and other connectors break the columns rebound and release energy as vibrations the vibrations help push dust, and even larger pieces out of the path of the dropping column, this happens in the lower section, however in the lower section also exhibits a reflection wave of the sound traveling back up the columns.

 

[ozeco41]

Really? Pray tell, what did I rest on BV, on what occasion?

This should be interesting...

You have to be kidding. I will not try to address levels of argument ranging down as low as childish evasive dishonesty whilst doing my best to encourage reasoned rational discussion.

I have already given a comprehensive response to your earlier challenge which you have discourteously ignored. Some weeks/months back I also challenged you over a snide comment you directed at me. You also ignored that.

Why ask for explanations if you intend to ignore them? I will never treat you with such rudeness.

 

[ozeco41]

No, not at all.
I am at a loss trying to comprehend how you could misread me so egregiously.

Your own speciality arena is explaining the actual collapse mechanism of the WTC collapses on a systems level, with engineering thinking.
You are great at that.


Myriad did not make a post that touches upon this speciality arena.
Neither did I.

Try again.

No.

If you are not prepared to address my reasoning I'm not inclined to keep respond to recycling of bare assertions.

Last time I checked the relevant posts in the thread both you and Myriad were discussing the BV paper which I understand is about the engineering of WTC collapses.

How this does not impact on engineering physics is beyond my simple comprehension.

If I'm mistaken and BV is not about engineering...I will abandon my errant sinful ways.

 

[Myriad]

You have to be kidding. I will not try to address levels of argument ranging down as low as childish evasive dishonesty whilst doing my best to encourage reasoned rational discussion.

I have already given a comprehensive response to your earlier challenge which you have discourteously ignored. Some weeks/months back I also challenged you over a snide comment you directed at me. You also ignored that.

Why ask for explanations if you intend to ignore them? I will never treat you with such rudeness.

Nothing you've said in those responses addresses what (and when and where) I "rested" on BV.

I gather that you want to continue to insist that I did so, without providing any evidence that I did. Very courteous indeed; I should be ashamed.

The truth is that the only time I have referred to BV at all in this thread (or, as far as I can recall, any others) is near the beginning, when Major_Tom asked a question specifically about BV ("what did Bazant mean by...?"). I responded with an explanation (over the course of a few posts) that the model in BV was based on the model in BZ, that the model in BZ was abstracted and idealized with limiting-case assumptions, and that Bazant had explicitly stated as much.

Major_Tom subsequently and repeatedly used that response to accuse me of misrepresenting BV as applying to the real world, the very opposite of what I actually said. This is obvious if you merely read the quotes of mine that Major_Tom keeps spamming in this thread. To conclude otherwise, as you've just done and have been doing for years, you'd have to take Major_Tom's accusations at face value, and just kind of glance at the quotes and say, "hmm, Myriad did mention BV, I guess Major_Tom must be right." That's why I accused you of uncritically parroting Major_Tom, and why I claim the evidence still points that way.

If you're as reasonable and courteous as you claim to be, show me where and how I've "rested on BV", or retract that, please.

 

[Crazy Chainsaw]

Go for it!

I don't like cross forum posting, but this is for you JSO.

https://www.physforum.com/index.php?showtopic=12383&st=120

The remnant of the core of the north tower (the spire) is seen oscillating laterally for a few seconds before it falls. The entire unit appears to fall at once, so the splices near the ground probably broke. If the splices had little strength, a transverse wave might be able to literally push a length of column laterally out of the splice. Someone would need to model it mathematically. The bare core didn't have anything else to give it stiffness laterally so it isn't surprising that it oscillated laterally. When it was still a part of the main floors and perimeter, it was still restrained. There's the energy associated with the impacts by the front and also the stored strain energy that was in the core before collapse that had to go somewhere as the core was unloaded during collapse.

The larger box columns at the bottom appear to be literally butted up against each other with perhaps a weld between them. A through-thickness weld would be next to impossible on columns that thick. If there were any plates welded to them, they must have been thin compared with the thickness of the box plate. I haven't seen any signs of thick splice plates. There doesn't appear to be much information on how the larger box columns on the core were spliced together.

The spire is where I first noticed the oscillations, thanks for pointing them out.
The building is an interdependent structure relying on the unity of the connected parts for strength a constantly building Oscillation destroys that unity, by allowing the components to act independently of the Structure.
Destroy the unity of the structure and it collapses like a house of cards.
In fact the only way the buildings can collapse, is though the destruction of the buildings unified strength!
The company in Japan that made the beams might have the data your looking for if they still exist, and no their were no reinforcing plates needed.
The Beams were made to be continuously welded, all that is needed is a tapered structure to the beam to allow access to the other side.
Constantly overlaying the weld onto the material while maintaining a constant temperature of the weld allows for and even and constant weld by keeping the welded part in a plastic liquefied state.
The you simply v out the section to be welded and keep the temperature constant using a Torch to control the temperature of the beam and weld, by the color produced though heating.
It is much harder to weld high carbon tool steels than low carbon structural steels
and I weld tool steel using the process all the time.



This post has been edited by Chainsaw, on Feb 8 2007, 02:16 PM

I ment columns but put beams, didn't have much time to post back then constantly working
And on the road. Always in a rush.

 

[Bravin Neff]

not in dispute - now take the next steps. Is WTC a valid example?

It might be. What it would allow you to do is take the timing (i.e., from video record) and from that, using their model, compute the crushing energy per unit height. Which they do for various timings.

The BV base premise is a 1D approximation which also calls up "crush down/crush up" which is itself a derivative of 1D. Specifically again it relies on column crushing energetics.

The general energetics are from floor displacement. I don't think it needs to be crushing columns, although their own wording specifies this. I say it could just as well be energy crushing regardless of what gets crushed - columns, floor joist-column connections, smashing concrete slabs, whatever.

Who is game to state their position on that assertion? Whether for or against - in the latter case giving reasons?

I just did.

1) Prove that BV does NOT model on 1D, column crushing energetics and CD/CU...

1D model, yes. Column crushing - yes as a sufficient answer, no as a necessary answer. As explained above.

2) Prove that even with those three in place it is a valid approximation.

I think it would be a valid approximation if the known WTC timings (from video or seismic records) jive with the crushing energetics per unit height (which needs to be independently known), along with the compactness layer (which needs to be independently known). If no one has done this work, then it is impossible to say if it is a valid or invalid approximation.

B&V use their model to compute the Wf (energetics per unit height) and also the compactness layer (their lambda) per different timings to ground (figure 6). But without independent means of determining these values, again, I think the question is impossible to answer.

 

[ozeco41]

It might be. What it would allow you to do is take the timing (i.e., from video record) and from that, using their model, compute the crushing energy per unit height. Which they do for various timings.

Yes - subject to the second criteria I've posted several times - the need to check sensitivity to gross changes in mechanism - to ensure the we are not seeing "right results for wrong reasons" which is one of those hard to detect insidious errors in engineering modelling and other aspects of applied science. My position still the same on that one. I cannot prove it is but it is up to those who make the claims to satisfy the validity of their assumptions - I would need to see that factor legitimately addressed rather than rely on mere authority of the postulating academics - if in fact they even recognise the issue.

The general energetics are from floor displacement. I don't think it needs to be crushing columns, although their own wording specifies this. I say it could just as well be energy crushing regardless of what gets crushed - columns, floor joist-column connections, smashing concrete slabs, whatever.

Thank you for that bit. And - yes - I agree it could well be several other energetics - exactly the point I made recently in suggesting how the Bazant desire to develop a generic 1D model may be chasing an unattainable goal BUT could possibly be made valid across the range of column spacings IF the energetics factor in the maths could accommodate the variations.

I just did.

A good start and heading in the right direction. There is an aspect of scope I will try to address once I get my head clear of the fog caused by all the noisy stuff on the thread. I don't want to risk making errors given that you are addressing the level of argument I can appreciate and respect.

1D model, yes. Column crushing - yes as a sufficient answer, no as a necessary answer. As explained above.

Agreed with the same reservation about the "scope" issue I want to address.

I think it would be a valid approximation if the known WTC timings (from video or seismic records) jive with the crushing energetics per unit height (which needs to be independently known), along with the compactness layer (which needs to be independently known). If no one has done this work, then it is impossible to say if it is a valid or invalid approximation.

Correct as far as it goes. But bear in mind that validation is not limited to maths though that is the most likely path. It could be by explanation of mechanism with less rigorous maths. We wont know till someone goes there. So I'm staying with the "Engineering Managers Position" - the basis on which I could l stake my professional reputation when assuring an astute client - for a billion or multi billion dollar project. I cannot rely on it without the assumptions being shown to be valid to a professionally supportable level.

Your point "If no one has done this work, then it is impossible to say if it is a valid or invalid approximation." supports what I say - I take the next step - I'm not accepting it as valid without proof. If strict proof is not possible I would look for a risk managed probabilities based assessment. Which takes us up one level further in the sophistication. BUT it can be sufficiently persuasive of validity IF someone does it. I don't limit the methods - merely identifying the need to see it done and done persuasively.

B&V use their model to compute the Wf (energetics per unit height) and also the compactness layer (their lambda) per different timings to ground (figure 6). But without independent means of determining these values, again, I think the question is impossible to answer.

The same key point as previous. Already explained.

Thanks Bravin - you are hitting the issues at the level I respect - put simply "We are near enough on the same sheet of music".