OOS Collapse Propagation Model

[MileHighMadness]

I recognize that you have put a lot of work into that book, and I respect that effort, but I'm simply asking, what is the point of all this? Do you believe you have found something of significance, and if so, what is it?

If you don't come to a point...no one can ever challenge you point of view. And T_M is the master of this.

 

[LSSBB]

If you don't come to a point...no one can ever challenge you point of view. And T_M is the master of this.

He came to a point a long time ago, as Beachwood reminds us. He just never revised it and won't discuss it.

 

[rwguinn]

I've skimmed it a couple of times, but since I'm not interested in your obsession with Bazant's mathematical crush-down/crush-up model, it was TL;DR in detail. If that's your only point, then I probably won't read it. To me, the important part of Bazant's papers is the energy analysis, and from that perspective it sounds to me like you're saying it wasn't crush-down/crush-up; it was much worse and less survivable than that because ROOSD takes less energy.

I recognize that you have put a lot of work into that book, and I respect that effort, but I'm simply asking, what is the point of all this? Do you believe you have found something of significance, and if so, what is it?

If you don't come to a point...no one can ever challenge you point of view. And T_M is the master of this.

He came to a point a long time ago, as Beachwood reminds us. He just never revised it and won't discuss it.

It takes a really special type to realize after 14 years of cogitation that if you overload the floor of a building, and it collapses onto another floor, whether in chunks or intact, that might possibly overload THAT floor so that it is likely to collapse onto the next lower floor...How the rest of us never even considered it, now that it's obvious, I'll never know
A phenomenon known even to rock climbers...

 

[LSSBB]

He came to a point a long time ago, as Beachwood reminds us. He just never revised it and won't discuss it.

Dang spell checker. I meant Beachnut.

 

[Major_Tom]

To me, the important part of Bazant's papers is the energy analysis, and from that perspective it sounds to me like you're saying it wasn't crush-down/crush-up; it was much worse and less survivable than that because ROOSD takes less energy.

The energy analysis is in Bazant and Zhou (2002).



The crush down, then crush up model is in:

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

Zdenek P. Bažant and Mathieu Verdure (BV), published in 2007



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. Bažant and Jia-Liang Le (BL), published in 2007


and


What Did and Did not Cause Collapse of WTC Twin Towers in New York

Zdenek P. Bazant, Jia-Liang Le, Frank R. Greening and David B. Benson, published in 2008


He also published another paper in 2011 on this subject.



You are certainly not the first person to confuse the energy analysis in the 2002 paper with the crush down, then crush up mechanics in the papers dating from 2007. The same confusion can be seen on the very first page of this thread and throughout this entire forum.

I recognize that you have put a lot of work into that book, and I respect that effort, but I'm simply asking, what is the point of all this? Do you believe you have found something of significance, and if so, what is it?

Thanks. The last section of the book is titled 'Conclusions.' That may be a good place to look for any conclusions drawn in the course of my research.


Would you like to know of the purpose of the OOS model or the conclusions of the book?

 

[DGM]

I recognize that you have put a lot of work into that book, and I respect that effort, but I'm simply asking, what is the point of all this? Do you believe you have found something of significance, and if so, what is it?

In short, he has concluded that he is the only one that truely understands the collapses.

One of the stated purposes of the NIST reports is to determine the how and why of each collapse in order to recommend changes to building codes. If they do not recognize the actual collapse modes of what seem to be the largest progressive floor collapses in history, how can they make appropriate code changes regarding collapse progression to make buildings safer? Also, if the proposed collapse initiation mechanisms of all 3 buildings are provably incorrect, how can code changes based on such faulty information lead to safer high-rise designs in the future? If the collapse modes of the Twin Towers remains unidentified within the NIST NCSTAR reports as progressive OOS floor failure, it seems obvious that effective codes cannot be rewritten to avoid another OOS progressive floor collapse.

The irony of this is, his book points out just how little he understands about construction, building codes and the purpose of the NIST. He offers no solutions and only points fingers.

I'd like to know this:

MT, based on your research, what building code changes should have been made and how do they differ from the ones the NIST did suggest?

That would actually be a conclusion to the "book".

 

[tsig]

The energy analysis is in Bazant and Zhou (2002).



The crush down, then crush up model is in:

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

Zdenek P. Bažant and Mathieu Verdure (BV), published in 2007



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. Bažant and Jia-Liang Le (BL), published in 2007


and


What Did and Did not Cause Collapse of WTC Twin Towers in New York

Zdenek P. Bazant, Jia-Liang Le, Frank R. Greening and David B. Benson, published in 2008


He also published another paper in 2011 on this subject.



You are certainly not the first person to confuse the energy analysis in the 2002 paper with the crush down, then crush up mechanics in the papers dating from 2007. The same confusion can be seen on the very first page of this thread and throughout this entire forum.







Thanks. The last section of the book is titled 'Conclusions.' That may be a good place to look for any conclusions drawn in the course of my research.


Would you like to know of the purpose of the OOS model or the conclusions of the book?

"THE END", ?

 

[WilliamSeger]

You are certainly not the first person to confuse the energy analysis in the 2002 paper with the crush down, then crush up mechanics in the papers dating from 2007. The same confusion can be seen on the very first page of this thread and throughout this entire forum.

I beg your pardon; I'm not confused between the two. I said I'm not interested in your "crush-down/crush-up" obsession and that I considered the energy analysis to be the important part of the papers.

Would you like to know of the purpose of the OOS model or the conclusions of the book?

I'd like to know what I asked: Do you believe you have found something of significance, and if so, what is it? If it's just arguing against Bazant's mathematical model as a literal description of what happened, then I'm not much interested in that argument -- unless you're claiming to infer more than that. For example, was it not the purpose of these detailed studies to find evidence that these were "assisted" collapses of some type? Did you find any?

 

[JSanderO]

​

I beg your pardon; I'm not confused between the two. I said I'm not interested in your "crush-down/crush-up" obsession and that I considered the energy analysis to be the important part of the papers.



I'd like to know what I asked: Do you believe you have found something of significance, and if so, what is it? If it's just arguing against Bazant's mathematical model as a literal description of what happened, then I'm not much interested in that argument -- unless you're claiming to infer more than that. For example, was it not the purpose of these detailed studies to find evidence that these were "assisted" collapses of some type? Did you find any?

ROOSD and is about the destruction / collapse associated with a very specific type of structure... long span column free interiors.... such as the twin towers.

The collapse was not a pancaking of floor slabs... it was not the crushing and buckling of columns... it was vertical avalanche of mass distributed over the entire floor foot print. This destruction of the floor plates rendered the facade unstable as well as the core columns which were also stripped of the bracing in an avalanche of floor material inside the core.

The columns which hold the building up were dependent on the floor plates and these were the "weak" link when they were rather easily overwhelmed by a relatively small dynamic load which in the case of the towers was released from mechanical damage related to the columns where were severed or buckled, or were pushed out of axial alignment from heat expansion of the bracing.

The OOS floor mass was all resting on a belt girder connect to the 24 perimeter core columns and this belt girder was cantilevers on beam stubs from those 24 columns. This was a design which was very vulnerable to a runaway failure... with little to no means to arrest it.

Once the mass (floor sections) was unsupported and was of a threshold value (relatively small) all the floor plates below succumbed and this dynamic load and led to the "undoing" (Euler buckling) of the columns... which not only held the floors and but held themselves up... no bracing... no can stand too tall!

The lesson here is the strong columns came down because they were completely depending on the floor plates to brace them and these plates were actually rather weak...and easily destroyed by falling mass...and it likely took only a few floors to start the vertical avalanche. ROOSD was both a global and local phenomena... Any local area was subject to the same pound per square foot loads from above and so the timing was not significant...Sooner or later the entire floor area was involved... and all confined by the tube of the perimeter.

ROOSD is the best fit description as to how THESE structural designs came apart from a descending mass in the OOS region. All the BS about crush up and crush down and column strength completely misses what took place and this can be easily seen by studying the vids and the images... something that Bazant apparently didn't bother with and the truthers likewise... and apparently, NIST and a whole bunch of JREFers. Tom and Femr2 did a rather good job at analyzing this and why others refuse to see this is bizarre to say the least... or would that be childish... can't possibly admit someone was more observant and more clever???

As far as the NIST mandate about future prevention of such disasters... it would have made sense for them to make some recommendations about hull and core long span floor systems which acted to brace the hull and the core. If fire alone could release the threshold floor mass and take the whole building with it... very robust fire suppression systems were in order... or these designs should be proscribed... because they ARE vulnerable to ROOSD. My opinion.

It doesn't matter what caused the mass to get going as far as the ROOSD process is concerned... once this mass was present the towers were goners. (the maths are probably pretty simple. The cause of the mass release... initiation... is a completely separate discussion.

Seeger open your eyes and cut the BS...

 

[carlitos]

So, no answer to this then?

Do you believe you have found something of significance, and if so, what is it?

 

[WilliamSeger]

ROOSD and is about the destruction / collapse associated with a very specific type of structure... long span column free interiors.... such as the twin towers.

Then ROOSD is too specific to be very useful. The general idea of cascading floor failures is not specific to long-span floors. The Skyline Towers building was a typical reinforced concrete structure with bays that were probably only 20 to 24 feet. That collapse was neither "pancaking" (if by that you mean whole floors dropping cleanly) or "crush down" by an intact top block. The floors were simply not designed to absorb the impact of the floors above falling on them; specifically, they weren't designed to transfer that dynamic load to the columns, so they sheared away from columns. The same thing was true with the corner collapse of the Ronan Point apartments except with load-bearing walls instead of columns, so the principle isn't even specific to column framing.

As far as the NIST mandate about future prevention of such disasters... it would have made sense for them to make some recommendations about hull and core long span floor systems which acted to brace the hull and the core. If fire alone could release the threshold floor mass and take the whole building with it... very robust fire suppression systems were in order... or these designs should be proscribed... because they ARE vulnerable to ROOSD. My opinion.

Another thing I'll take issue with is that I don't see anything in the NIST report that implies that they took Bazant's theoretical crush-down model as a literal description of what happened (as you seem to think it was intended to be), or that it had anything to do with their recommendations, or lack thereof. All I see is that they accepted his energy argument that the collapse was unstoppable after it got started. Furthermore, I would not expect to see any code changes that require resistance to that kind of progressive vertical collapse; it would add too much cost. The NIST recommendations were instead aimed at preventing what they took as the initiating events in the particular case of the WTC towers, as I would expect.

Seeger open your eyes and cut the BS...

Okay, but that advice would be more helpful if you could please point out the BS.

 

[JSanderO]

I am not familiar with skyline tower... but it apparently collapsed because shoring was removed from uncured concrete. Apples and oranges. Did the entire building collapse? Why is this in any way similar to the twin towers?

 

[WilliamSeger]

I am not familiar with skyline tower... but it apparently collapsed because shoring was removed from uncured concrete. Apples and oranges. Did the entire building collapse?

Yes, the "entire" building (up to an expansion joint between two structural-independent sections) collapsed into the basement. (Edit: that includes at least 21 or 22 floors that were fully cured, if that's what your thinking.)

Why is this in any way similar to the twin towers?

Because in both cases, as well as the Ronan Point apartments and other cases, the floors were simply not designed to transfer the dynamic load of collapsing floors above. There was no code requirement to do so, and I seriously doubt there will ever be any such requirement, and not many building owners will take on that extra expense if it isn't a requirement.

 

[Stamuel]

Here is what I take away from the work on ROOSD: It is an attempt to be as specific, detailed and precise as possible about how the buildings actually collapsed (the propagation part, anyway). There is no requirement that every detail have some major significance for building safety or CD debates. Still, ROOSD could be useful if someone goes crazy about some detail from videos of the collapses, because you will already have a fairly complete and detailed description of what happened, assuming it is correct, of course.

 

[carlitos]

So, no answer to this then?

Do you believe you have found something of significance, and if so, what is it?

 

[jaydeehess]

.
NIST, in essence, agrees with Major Tom. Shall we all just take note of that for a few moments.

From NIST FAQ.http://www.nist.gov/el/disasterstudies/wtc/faqs_wtctowers.cfm

Since the dynamic amplification factor for a suddenly applied load is 2, an intact floor below the level of collapse initiation could not have supported more than six floors. Since the number of floors above the level where the collapse initiated exceeded six for both towers (12 for WTC 1 and 29 for WTC 2), neither tower could have arrested the progression of collapse once collapse initiated. In reality, the highest intact floor was about three (WTC 2) to six (WTC 1) floors below the level of collapse initiation. Thus, more than the 12 to 29 floors reported above actually loaded the intact floor suddenly.

This is a simplified model description of the collapse but NIST is saying that the floor to column connections were massively overloaded. That is not to say that an entire floor pan failed in one piece(so-called 'pancake' collapse). It standsa to reason that in a structure that was damaged more by impact in some regions, that those areas saw failure earlier. It stands to reason that a tilted upper , falling mass would impact lower regions on its lower edge first.
AFAIAC , MT's details as to what portion of the building went first is the only part that may be debated , and that's not really relevant to a characterization of how the collapse progressed.

Upper mass began coming down. Columns sections of upper falling mass CANNOT, at that time, be aligned with their original lower sections. THEREFORE the structures that will be hit by this falling mass is, by a vast margin, the floor pans. The only debate then would be what fails first, floor pan or truss connections to columns. (and it hardly matters, if either fails then collapse progresses further, mass increases, velocity increases, and collapse just keeps going. Columns are left there with nothing supporting them laterally)

More like rediscovered what NIST already had.
More quantified perhaps, significance debatable

 

[rwguinn]

More like rediscovered whathas come to realize that all those real engineers and NIST already had. actually had an inkling of what they were talking aboutMore quantified perhaps, significance debatable

But we were all wrong--we said a bracket broke, but it was actually a gusset on the bracket that broke first.
Or maybe it was we thought the upper right bolt in the 4 bolt pattern failed first, when it was actually the upper left...

 

[Major_Tom]

Do you believe you have found something of significance, and if so, what is it?

Absolutely. It is implied in the fact that I took the time and effort to put the website together. The website and book describe what I have found.

If it's just arguing against Bazant's mathematical model as a literal description of what happened, then I'm not much interested in that argument -- unless you're claiming to infer more than that.

Bazant is just one example of a much larger pattern.

For example, was it not the purpose of these detailed studies to find evidence that these were "assisted" collapses of some type? Did you find any?

The OOS mappings are just one part in a larger set of mappings which includes the initiation mappings of WTC1, 2,and 7. This thread was originally set up to cover only the OOS propagation mappings, or colapse progression.

Shortly after this thread was started I introduced another thread on the WTC1 initiation mappings. The details contained within that thread were eventually condensed into the form which exists within the book.

The initiation mappings are unquestionably the most accurate, detailed mappings of the observable initiation sequences of WTC1, 2, and 7 existing anywhere.. This is easily verifiable simply by comparing them to any other mappings or descriptions whiich exist in the written technical history of the collapses.

It is impossible to approach the highly charged and controversial subject of demolition without examining the initiation sequences of the buildings.


How were these mappings received within this forum? The thread on the initiation mappings was removed from this subforum. The reason given was, no joking, that the mappings had nothing to do with "conspiracy theories".


From the conclusions of the book:

A key Achille's heel in study and discussion of these subjects over the last decade can be spotted simply by observing the different attitudes people have toward collections of observations and measurements.

The general attitude within this subforum toward observation and measurement of the initiation sequences is well recorded. The reactions demonstrate conclusively a surreal level of ignorance of the subject matter.

 

[Major_Tom]

Were I to sum up this forum in one word, I would choose the word 'smear'.

I could also sum up the purpose of this forum in a single sentence. It is to downplay or ignore all contradiction to a particular world view expressed among regular posters here.


Anyone who challenges or identifies contradictions within this world view is 'smeared'.


.....................................


The collective mappings, of which the OOS model is only one part, challenge world views of this forum on a fundamental level. They also challenge many statements made by a group like AE911T. That must, of course, be countered by an almost continuous 'smear' or simply by ignoring them. This is encountered from the first page of any thread which I have started here including this thread.


From the conclusions of the book:

First and foremost it is necessary to recognize the confusion surrounding the collapses which exists on all technical levels. For many people this is very hard to do. Many will not recognize this within themselves, but perhaps they can recognize it in others as it is quite visible if one makes the effort to see it.

This is probably the most fundamental difference between the general world view within this forum and conclusions of my own research. I recognize confusion surrounding the collapses on all technical levels, from the NIST and Journal of Engineering Mechanics publications to what is commonly repeated within forums on this subject.

The general world view here seems to recognize contradiction within those who are perceived as 'opponents' but not within the overall written technical history of the collapses.

My website maps contradiction within the visual and written records of the collapses. These contradictions are predictably met with smear and simplified historic revisionism within this environment.

 

[Spanx]

Were I to sum up this forum in one word, I would choose the word 'smear'.

I could also sum up the purpose of this forum in a single sentence. It is to downplay or ignore all contradiction to a particular world view expressed among regular posters here.


Anyone who challenges or identifies contradictions within this world view is 'smeared'.


.....................................


The collective mappings, of which the OOS model is only one part, challenge world views of this forum on a fundamental level. They also challenge many statements made by a group like AE911T. That must, of course, be countered by an almost continuous 'smear' or simply by ignoring them. This is encountered from the first page of any thread which I have started here including this thread.


From the conclusions of the book:




This is probably the most fundamental difference between the general world view within this forum and conclusions of my own research. I recognize confusion surrounding the collapses on all technical levels, from the NIST and Journal of Engineering Mechanics publications to what is commonly repeated within forums on this subject.

The general world view here seems to recognize contradiction within those who are perceived as 'opponents' but not within the overall written technical history of the collapses.

My website maps contradiction within the visual and written records of the collapses. These contradictions are predictably met with smear and simplified historic revisionism within this environment.

So where is the conspiracy or are you just trying to make one ?