OOS Collapse Propagation Model

[DGM]

What had to have happened (Mr B et al) is that some how SOME amount of mass was disengaged from the structure and fell... It fell not on COLUMNS... but it fell on FLOORS.

So you are saying if the floors were stronger the building would not have failed?

Do you think the Empire State Building could take the same hit and not collapse? If so, why?

My feeling is the ESB wouldn't have lasted as long and likely collapsed at impact.

 

[beachnut]

If this is the *case* Mr B makes... it's really hooey in a sense... totally akin to Gage's 81 columns disappearing over 8 floors in an instant. Mr. B... you can't get the top section to drop straight down with dynamic load from a 12' drop. It's idiotic to bother to even contemplate such absurdity.
...

You can't do the math. Please write a letter to Mr B, get it published, we need a good laugh.

Why do you hate engineering so much?

You really have no clue what a model is, and no clue how to relate a model to reality. E=mc², a math model, wait till you see the math needed to explain it, you would be calling Mr E's work hooey.

Like the rock slide BS, you don't understand engineering, and prefer to BS about it.

You don't understand math and engineering models -

 

[carlitos]

If this is the *case* Mr B makes... it's really hooey in a sense... totally akin to Gage's 81 columns disappearing over 8 floors in an instant. Mr. B... you can't get the top section to drop straight down with dynamic load from a 12' drop. It's idiotic to bother to even contemplate such absurdity.

Jesus Christ. No one is "getting" the top section to drop straight down. IT'S A LIMITING CASE!!!! Read the first handful of pages in this thread. Limiting. Case.

http://en.wikipedia.org/wiki/Limiting_case_(mathematics)

 

[jaydeehess]

Jesus Christ. No one is "getting" the top section to drop straight down. IT'S A LIMITING CASE!!!! Read the first handful of pages in this thread. Limiting. Case.

http://en.wikipedia.org/wiki/Limiting_case_(mathematics)

I don't know how many times it has to be repeated that Bazant is not trying to say that this was THE what-really-happened senario.

The purpose is to show that even if this were the case, a scenario (though highly IMPROBABLE to the point of impossible scenario) which would work in the greatest possible favour of collapse arrest, and yet even in this extremely improbable/impossible hypothetical scenario, collapse would continue.

How then could anyone make any other scenario that would demonstrate collapse arrest would occur?

 

[jaydeehess]

There appears to have been something else going on. That was the columns were being compromised... first by the plane strike and then by heat related process.. The net result was that these processes OVER time drove down the capacity of the columns that we left and they couldn't support the loads and so they buckled and this released the rest of the mass which hadn't been freed from the structure and fallen (on to floors).

So the interesting thing... to me... is HOW did the heat work from impact to release?

a) did it drive the capacity of enough columns down for them to buckle under the constant load?

b) did it cause the connections to fail leading longer unbraced column length and columns with decreased capacity?

c) did it cause the frame to warp... columns pushed laterally from expanding bracing... with axial alignment destroy and OAL (aggregate) column capacity driven down below service loads?

One of, All of the above or a combination of them. Or perhaps someone has some other ideas about how heat did it.

This is what was going on Mr B and your math has nothing to do with any of the above. I am sure your math is fine... but it has nothing to do with the collapse of the top section of the towers now with the collapse of the undamaged lower section.

But all of that you post here has to do with the cause of initiation, not copntinued progression of collapse. It would be absurd to expect that the heat on the impact floors was affecting the strength of columns well below the impact floors.

Your queries here are relevant but not in reference to collapse progression.

Bazant was addressing collapse progression and developed a scenario that would be most favourable to collapse arrest **after initiation**. Even in this posited scenario though he determined the collapse would continue.

 

[ozeco41]

The limit case is the falling upper section imparting its entire dynamic load onto, or transfered to, the columns. Bazant's calcs on that limiting case, which is the best case senario for collapse arrest, indicates that the columns could not withstand that load had this limiting case been the reality..

That IS NOT to say in any way shape or form that it is expected that the entire dynamic load WAS transfered to the columns. Its a hypothetical limiting case.

That's how I see it.

That much is true for BZ 2001/2. But it is only part of the scenario.

And it is also the bit that most members posting are already agreed on. (The exceptions being:
- tfk whose post in another thread caused the resurrection of this thread and - so far - has not backed up his multiple false assertions; and
- beachnut whose comment "OOS==BS" is ambiguous)

BUT that part is not what the legitimate ongoing discussion is about and not what it should be about to stay "on-topic" and focussed. There is a lot of not legitimate "off-topic" fog being posted.

HOWEVER the legitimate core issues still being misunderstood or not addressed are:
1) OOS or ROOSD or whatever else we call it was the leading mechanism of progression for the "Twins" collapses. STATUS IMO - No one disagreeing with the mechanism AFAICS despite lots of disagreement with the label and aspects of M_T's explanations.

2) Bazant as in BZ was a limit case. STATUS IMO - No one disagreeing. (A side issue which I have raised several times - the recent paper by Sz, Sz and J shows a plausible argument that Bazant's maths was wrong - and there wasn't enough energy. I'm prepared to leave that on one side but it has not been rebutted AFAIK.)

3) Bazant as in BV and the later papers was a one-dimensional "columns in line model" which is not what happened at WTC on 9/11 - Bazant et all apply that model to WTC collapses as if it was what happened and NOT as a limiting case. STATUS - Bazant et al are wrong when they apply it to WTC 9/11 real event. "Crush-down crush-up" as defined by B et al does not apply to WTC real event. Those claiming BV was a limit case are wrong. If I'm wrong on those three claims someone show me - I've made the statements multiple times and they are variously fatal to the false claims being repeated by numerous debunkers. Major_Tom has them right.


4) There is still a lot of confusion - misunderstandings - foggy thinking - evasion of simply stated explicit claims and denials by vague generalisations or ambiguous conflations. STATUS: Should be self evident. Isn't. A lot of people need to back off from attacking M_T - focus on what the core issues are - re-read BV and correct false understandings. Those who say they aren't interested ask why they keep posting snide off-topic comments in this thread. Those who keep trying to change the topic ditto. Those who still insist on needing maths (or FEA) to clarify a descriptions of a mechanism need to clear up their own understanding of basics.

perhaps I'll start a poll.

How could you frame questions - in Poll format - which would force anyone to think clearly? The poll would simply reflect the split of confusions which already exist.

 

[tsig]

From my perspective... there is not much to discuss about ROOSD. It seems like the best fit explanation and I don't see any loose ends.

The issue is how did the driving ROOSD mass get *created*.

And then there is the issue of the 9/11 community both side, all sides not embracing this explanation and instead sort of attacking the messenger... mostly on style. Obviously the simple ROOSD explanation was missed by most people who were interested in the collapses. But now you have a few who claim... no biggie... a rose by any other name is a rose and it's just global collapse so what the big deal?

Tom seems to find it interesting how so many people refuse to see how the big guys who were cited as the next best thing to sliced bread re the collapse math... were really off the mark. And that's pretty remarkable. Lot of hubris here fellas. This sort of thing may have prevented intelligent people from acting intelligently and confronted with that they resort to ridicule.

Very telling...

You still don't understand the mark they were aiming at.

 

[ozeco41]

You still don't understand the mark they were aiming at.

If he doesn't he is not alone.

Here's my take - there are three relevant marks:
1) BZ - a quick back of the envelope "limit case";
2) BV (and other later papers)
(a) - a generic model for analysing future collapses including those from CD;
(b) - uses WTC collapses as models by applying the one-dimensional model to the real event.

Did Bazant et al "hit the marks"?
1) Hit the mark.
2)(a) Progressed towards the mark and added to the body of academic work;
2)(b) Missed the mark.

 

[DGM]

3) Bazant as in BV and the later papers was a one-dimensional "columns in line model" which is not what happened at WTC on 9/11 - Bazant et all apply that model to WTC collapses as if it was what happened and NOT as a limiting case. STATUS - Bazant et al are wrong when they apply it to WTC 9/11 real event.

Were they actually framed to imply it was the real events or if their model was applied that way? (I never followed them that far because it was irrelevant to my understanding).

I can see how applying them this way could be useful. (model design wise).

 

[ozeco41]

Were they actually framed to imply it was the real events or if their model was applied that way? (I never followed them that far because it was irrelevant to my understanding).

They are absolutely explicit that their model is:

A simplified one-dimensional analytical solution of the collapse front propagation will be presented. It will be shown how this solution can be used to determine the energy absorption capability of individual stories if the motion history is precisely recorded. Because of the shroud of dust and smoke, these histories can be identified from the videos of the collapsing WTC towers only for the first few seconds of collapse, and so little can be learned in this regard from that collapse.

So it is "one-dimensional" AKA "columns in line". Not what actually happened. The remainder of the paper is framed as if it did apply - recall they are using WTC collapse as

The most infamous paradigm...

(BTW Like all these papers it is a heavy read... )

I can see how applying them this way could be useful. (model design wise).

Without a doubt BUT any model has to adequately match the prototype. And the difference between "ROOSD" at WTC "Twins" and the homogenised collapse - columns doing the bulk of the resisting - of a more conventional structure invalidates the generic model for explaining WTC collapses. I can flesh out the explanation if you need it - here or PM.


BTW That is only one of the issues of the current confusions in the thread. The two mechanisms are vastly different BUT I don't think many members are confused over that aspect.

Some members may be confused and thinking that applying 1D models to the real event is OK. It can be - if you know exactly what you are doing but it isn't in this specific case of WTC "Twins" on 9/11. Remember that Bazant et al have no clear understanding of the collapse mechanisms to the level most of us here enjoy. <<That may attract some fire but I'll leave it in.

 

[DGM]

They are absolutely explicit that their model is:

So it is "one-dimensional" AKA "columns in line". Not what actually happened.

That's what I thought

The remainder of the paper is framed as if it did apply - recall they are using WTC collapse as

Also what I thought.

Without a doubt BUT any model has to adequately match the prototype. And the difference between "ROOSD" at WTC "Twins" and the homogenised collapse - columns doing the bulk of the resisting - of a more conventional structure invalidates the generic model for explaining WTC collapses.

But, It was never meant as an explanation for the collapse. I think the model building was meant to be more generic than perceived. Perhaps leaning more toward the structure type.

I can flesh out the explanation if you need it - here or PM.

Thanks but, I'm too old to start understand engineers..............

BTW That is only one of the issues of the current confusions in the thread. The two mechanisms are vastly different BUT I don't think many members are confused over that aspect.

I know I'm not.

Some members may be confused and thinking that applying 1D models to the real event is OK. It can be - if you know exactly what you are doing but it isn't in this specific case of WTC "Twins" on 9/11. Remember that Bazant et al have no clear understanding of the collapse mechanisms to the level most of us here enjoy. <<That may attract some fire but I'll leave it in.

Their purpose was clearly different. Why anyone would apply their work to the observable events is anyones guess. I know of only a very few that have, and they're not interested in the truth.

 

[ozeco41]

That's what I thought
...
Also what I thought.
...

OK - we are on same music.

But, It was never meant as an explanation for the collapse. I think the model building was meant to be more generic than perceived. Perhaps leaning more toward the structure type.

Without doubt. IMO the references to WTC were not their primary focus nor were they interested in avoiding adding to confusion among internet forum members. But many internet posters use the papers as primary references in discussions with truthers and that is one place where the confusions start.

Thanks but, I'm too old to start understand engineers..............

I've been doing it for far too many years. Most of my career was managing engineers and engineering and other "applied scientists" in the complicated real world. The narrow focus "forests v trees" aspects we see in many posts here have been bread and butter for me. (also "alligators v swamps" which is a different slant on the same syndrome. ) Take engineers out of their comfort zone of predetermined processes etc.....

Got kicked out of a couple of jobs over the years because I dared to challenge the prevailing wisdom of the narrow focus brigade. And I was an engineer - which somehow makes the sin of lèse majesté worse. One who is allegedly "one of them" daring to disagree. Ranks as "high treason". Made it worse that I was right.

I even dared to challenge R Mackey on this forum in my "newbie" days.

I know I'm not.

I recognise that.

Their purpose was clearly different. Why anyone would apply their work to the observable events is anyones guess. I know of only a very few that have, and they're not interested in the truth.

Actually there are quite a few examples from debunker members here - both in this thread and going back over history. .... But I've been resisting the temptations to carve up a lot of the more off focus/wrong/ad hom postings.

 

[rwguinn]

The only foggy thinking around here is by Truthers, apologists for truthers, and Engineering managers.
The arguments presented by M_T and his defenders are of the nature of "All these degreed engineers say bolt 1 failed in the 4 bolt pattern. I can prove it was actually Bolt 3, but I'm not going to show you how I know it"
Once collapse started, it was going to continue. It is a chaotic event, and absolutely not feasible to analyze in absolute detail. Simplifications are sufficient.
Enjoy the congratulatory party, Oz, M_T, and JSO.
We're done here.

 

[Newtons Bit]

Were they actually framed to imply it was the real events or if their model was applied that way? (I never followed them that far because it was irrelevant to my understanding).

I can see how applying them this way could be useful. (model design wise).

BV explicitly states that it is a model for purposes other than modeling how WTC actually collapsed. Why people choose to ignore this, I don't know. But I pointed it out in post #3 of this thread.

 

[WilliamSeger]

3) Bazant as in BV and the later papers was a one-dimensional "columns in line model" which is not what happened at WTC on 9/11 - Bazant et all apply that model to WTC collapses as if it was what happened and NOT as a limiting case. STATUS - Bazant et al are wrong when they apply it to WTC 9/11 real event. "Crush-down crush-up" as defined by B et al does not apply to WTC real event. Those claiming BV was a limit case are wrong.

I still consider BV to be a limit case, because under the simplifying assumption that the floors and connections were strong enough to transfer all loads to columns, column-to-column impacts would not be necessary to make the one-dimensional analysis valid. It's fair enough to say they weren't that strong, but I don't see why you think it's not a limit case. I'm not a structural engineer, but having worked with them, it is my understanding that such simplifying assumptions are often necessary to make a problem tractable, and even though they aren't "realistic" they are "close enough" to be useful -- especially when the only alternative is guess-work. In my layman's reading of BV (admittedly years ago), it does appear that they think their model meets that requirement, but I'm not convinced that they take it as a "realistic" description of what actually happened.

 

[ozeco41]

BV explicitly states that it is a model for purposes other than modeling how WTC actually collapsed.

Correct - as far as it goes.

Why people choose to ignore this, I don't know.

Who is ignoring it? Certainly not me. I have explained explicitly all the aspects of BV which are relevant to the topics of this thread - both the topic as focussed in the OP and the topic aspects under discussion since M_T resurrected this thread in response to a set of false claims by tfk. So who do you think is ignoring the clearly stated objective of BV? And why is that aspect relevant to the confusions which are under discussion here? Surely taking that single aspect out of context IS the focus of much of the confusion?

But I pointed it out in post #3 of this thread.

I suggest it would be prudent to not refer to that post or those adjacent to it in that first page. They are not the sort of posts I would be proud of if I had made them. I would be grossly embarrassed if I had put those sorts of comments on the public record.

 

[jaydeehess]

perhaps I'll start a poll.

Done
http://www.internationalskeptics.com/forums/showthread.php?t=281469

 

[pgimeno]

Correct - as far as it goes.

Who is ignoring it? Certainly not me. I have explained explicitly all the aspects of BV which are relevant to the topics of this thread - both the topic as focussed in the OP and the topic aspects under discussion since M_T resurrected this thread in response to a set of false claims by tfk. So who do you think is ignoring the clearly stated objective of BV? And why is that aspect relevant to the confusions which are under discussion here? Surely taking that single aspect out of context IS the focus of much of the confusion? I suggest it would be prudent to not refer to that post or those adjacent to it in that first page. They are not the sort of posts I would be proud of if I had made them. I would be grossly embarrassed if I had put those sorts of comments on the public record.

Yeah, misspelling "Verdure"... Shame on you, NB.

 

[ozeco41]

I still consider BV to be a limit case,

I understand that you do. Thanks for entering serious debate - something I have been trying to initiate for some time.

because under the simplifying assumption that the floors and connections were strong enough to transfer all loads to columns, column-to-column impacts would not be necessary to make the one-dimensional analysis valid.

IIRC you made those points in an earlier post. I'm not certain that I understand your reasoning but let me address the points in sequence:
(a) I will comment later on "simplifying assumptions" BUT the requirement for any such assumption is that it still adequately represents the real thing. The assumptions in BV do not validly represent the real WTC event - that is one of the central issues of confusion here.
(b) As for your specific reasoning - transfer of "all loads to columns" - such did not happen in the WTC real event nor AFAICS was it one of the explicit claims in BV. I can explore those two aspects further with you if you wish. i.e,. "what really happened" and the distinct separate issue of "what BV assumes."
(c) Then "column-to-column impacts would not be necessary":
___(i) I'm not sure about "impacts" - which seems to be a separate issue. I hope I haven't added to confusion. The distinction is between "columns involved" explanations as per the Bazant papers and "columns not (significantly) involved" explanations which are is what most of us are agreed were the real event.
___(ii) Columns "in line taking loads" is the main thrust of BV - including the "crush-down crush-up" model where the maths basis is based on "homogeneity" AKA "one-dimension" AKA "columns in line". Choose your own jargon.

It's fair enough to say they weren't that strong, but I don't see why you think it's not a limit case.

It is not a "limit case" as used by BV in the paper BUT they link it to BZ and that adds to the confusion of many posting members who refer to it - whether Bazant et al were confused or not the paper doesn't help members here to avoid confusion.

I'm not a structural engineer, but having worked with them,

I am and I have. Sorting out the "forests v trees" issues is a lot easier - in real life - face to face - when you are the boss - and (hopefully ) right. (And grossly embarrassing when you are the boss and get it wrong )

it is my understanding that such simplifying assumptions are often necessary to make a problem tractable, and even though they aren't "realistic" they are "close enough" to be useful

That is true but two points are relevant here:
(p) The assumptions MUST still be valid within the range of error you are able to account for. I can explain that further if it is not clear when stated to briefly - I am agreeing with your requirement - the results MUST be"close enough" to be validly useful.
(q) The situation here is actually a lot simpler than most are reading it. And it is because of the overlaying "need" to ridicule Major_Tom et al. The OOS model is correct and explains the real event. BV adds nothing - in the context of current discussions - to understanding the real event whether or not the concerns about BV are true or false. must

-- especially when the only alternative is guess-work.

There is no need for guess work to explain the real event because:
(s) The mechanism labelled ROOSD accurately describes the specific mechanism which led the progression collapse stage for both "Twins". (That includes M_T's OOS version which addressed two of the three sub-mechanisms OR my version which addresses all three mechanisms OR anyone else's versions which say the same things.)
(t) The actual energies/forces/impacts available for the progression ROOSD stage were overwhelmingly higher that the floor joist to column connections could withstand. No maths other than "ball park" guesstimates is needed to prove the point.

In my layman's reading of BV (admittedly years ago), it does appear that they think their model meets that requirement,

It is not an easy read but you could try reading again taking into account the points I have been raising.

but I'm not convinced that they take it as a "realistic" description of what actually happened.

Probably not - but that is where they add to the confusions.

Thanks again for the comments.

 

[ozeco41]

Yeah, misspelling "Verdure"... Shame on you, NB.

No - but I'm trying to avoid explicitly rebutting those ancient (2010) posts loaded with arrogant nonsense, personal attacks and technical errors.

I recently re-read the first dozen or so pages of the thread.

It was not a professionally satisfying experience.

If you must quote me would you please comment on what I said - no need to sink to ridicule.