Bazant in a nutshell

[Oystein]

This is a request to those posters who feel qualified^*) to discuss the several papers by Zdenek Bazant and co-authors on the WTC collapses. I must admit I am somewhat confused on what papers are out there, what hypotheses they propose, what their premises are, what they conclude - and how relevent they are on what level. Too big a hurdle for me to master alone at this point in time.

So could you give me "Bazant in a nutshell"?

Here's what I'd love to see in your first post in this thread for ideally each paper:

• Authors, Title, journal and date of publishing
• URL to a free download, if possible
• An abbreviated abstract: What is the main thesis or theses of the paper?
• What is the object of the paper? (For example "a general steel-frame highrise" or "a simplified, generalized model of TTs" or "detailed model of TT" or "observations of the actuall collapses of TTs")
• What is the top level objective of the paper? (E.g. "show that complete collapse is in general possible for a building like the TTs", "show that collapse progression is likely specifically in the case of TT" or "proof that there was no CD")
• What are the main premises of the paper?

Add whatever you feel is important to know for a non-engineer like me who wants a good introduction to Bazant! Don't get lost in detail!

In addition, if you like to give me your personal and short general assessment of the paper, feel welcome, but again, don't get lost in detail. And please, don't start pouncing on the poster above you before you have given this OP your own shot first! Suspend attack mode at least while we are on page 1, please. I'd appreciate!


Basically, I want this thread to be a point of reference, since the several Bazant papers get mentioned and criticized so often in this forum or elsewhere. Would be great if I could get such a short introduction from two or three of you on the first page!

Thanks!


*) I am looking particularly at
- tfk
- Major_Tom
- ozeco41
- ...

 

[femr2]

In a nutshell, the original outcome was that Bazant showed that there was enough energy available for complete destruction of a tower, given a 1 storey free-fall drop at the initiation zone, and some conditions favorable for survival.

Such conditions included full buckling of every column at every storey (rather than the lesser energy requirement to break column splices every 3 storeys), the limiting case.

Much has been said and inferred beyond that simple energetics based "proof" and the authors themselves ended up applying the virtual energetics based 1D model too literraly to reality.

Bazant showed their was enough energy available.

Might be useful for you to read the following thread...
Applicability of Bazant's model to the real world

 

[Oystein]

Ah, right!

So we have these papers by Bazant, with others:

1. [B 2001]: Bažant, Z.P. (2001), Why Did the World Trade Center Collapse?. Siam News, Vol. 34, No. 8, pp. 1 and 3.
2. [BZ 2002]: Bažant, Z.P.; Zhou, Y. (2002), Why Did the World Trade Center Collapse?—Simple analysis. Journal of Engineering Mechanics ASCE 128 (No. 1) pp. 2-6, with addendum March (No. 3), pp. 369-370. It's an expansion of the former with corrections, appendices and an addendum published later.
3. [BV 2007]: Bažant, Z.P.; Verdure, M. (2007), Mechanics of Progressive Collapse: Learning from World Trade Center and Building Demolitions. Journal of Engineering Mechanics ASCE 133 (No. 3), pp. 308-319.
4. [BLGB 2008]: Bažant, Z.P.; Le, J.-L.; Greening, F.R.; Benson, D.B. (2008), What did and did not cause collapse of World Trade Center twin towers in New York. Journal of Engineering Mechanics ASCE 134 (No. 10), pp. 892-906.
5. [BL 2008]: Bažant, Z.P.; Le, J.-L. (2008), Closure to "Mechanics of Progressive Collapse: Learning from World Trade Center and Building Demolitions" by Zdeněk P. Bažant and Mathieu Verdure. Journal of Engineering Mechanics ASCE 134 (No. 10), pp. 917-923.

With that out of the way (the first bullet in my opening post) now on to the main theses, objects and objectives!

 

[The Big Dog]

I've written a song about it, it goes like this:

First Soloist: Bazant, in his first book wrote about... fa la la...

Second Soloist: Bazant in his first book wrote about...

Tenors: He wrote about...

(They continue contrapuntally, in madrigal, until they rallentando to say...)

All: Bazant in his first book wrote about the... (gong sounds)

 

[Major_Tom]

4 papers linked and reviewed here:


2.6: Bazant Misrepresentation of Collapse Progression


Main thesis reproduced for each of the 4 papers in the reviews.

Comments on application by David Benson, one of the authors of BLGB reproduced near the end of the reviews.

 

[Oystein]

4 papers linked and reviewed here:


2.6: Bazant Misrepresentation of Collapse Progression


Main thesis reproduced for each of the 4 papers in the reviews.

Comments on application by David Benson, one of the authors of BLGB reproduced near the end of the reviews.

Excellent! The first time ever you made me interested in reading any part of your book

 

[beachnut]

4 papers linked and reviewed here:


2.6: Bazant Misrepresentation of Collapse Progression


Main thesis reproduced for each of the 4 papers in the reviews.

Comments on application by David Benson, one of the authors of BLGB reproduced near the end of the reviews.

You are unique, celebrating you don't understand models. You publish the proof in a book with no conclusion.

 

[LSSBB]

4 papers linked and reviewed here:


2.6: Bazant Misrepresentation of Collapse Progression


Main thesis reproduced for each of the 4 papers in the reviews.

Comments on application by David Benson, one of the authors of BLGB reproduced near the end of the reviews.

Has Bazant ever addressed the fact that a significant part of the core remained standing after perimeter collapse?

 

[ozeco41]

Has Bazant ever addressed the fact that a significant part of the core remained standing after perimeter collapse?

No. AFAICS he has never tried to explain the actual mechanisms of WTC 9/11 collapse - specifically the fact that global collapse of the twin towers involved three distinct and separable mechanisms viz (1) floor pancaking strip down which Major_Tom has labelled "ROOSD"; (2) Peel off and fall over of the outer perimeter columns in various sized sheets, some very large; AND (3) The strip down of the core leaving standing the "spires" that you refer to LSSBB.

All the various flavours of Bazant are theoretical abstractions which have never taken into account the actual collapse mechanisms OR later research which has progressively revealed more details of actual collapse mechanisms.

This set the basis for the two schools of thought on explaining WTC 9/11 collapses - viz:

1) those who are by far the majority and follow Bazant's "theoretical abstractions" or similar approaches; AND
2) the much smaller group who explain the collapses from the basis of the actual observed mechanisms.

These two are simply not very compatible and there has been a lot of confusion where people mix the two improperly.

I am a member of the second group and I explain from the basis of what actually happened. Bazant's theoretical abstractions are of limited value and I have for some years tried to not slavishly follow him where his models go beyond their validity.

Major_Tom and femr2 are two notable members here who also explain the actual mechanisms. This leading to the situation where some members presume that both M_T and femr2 must be wrong because they have been branded "truthers". Illogical abuse being loaded on them and on me when I have publicly agreed with them. A quite funny situation if you don't take it seriously - the oft repeated nonsense claim that everything a branded truther says must be wrong. That nonsense claim made either implicitly or, more rarely, stated explicitly. And my tongue in cheek comment in response that were a "branded truther" to claim "the cloudless daytime sky is blue" the anti truther mindset would cause some folks to deny the blueness of the sky. That vehement denial based on the assumed undeniable premises that (A) A "truther" said it and (B) "everybody knows that truthers are always wrong".

A quaint situation really, and based on false extrapolation of Bazant theories improperly applied to real world events....

...and my possibly cynical view of the "two polarised mindsets" school of 9/11 discussion.

 

[Oystein]

Is it so difficult to describe the premises, objects, and objectives of the 4 Bazant papers?

M_T's chapter 2.6 is helpful, no doubt, but isn't very focussed in its description of the Bazant papers. Lots of mixing of description and critique, and very much dwelling on the crush-down-crush-up topic. Is that really the main thesis of one or two of the papers - that "crush-down occurs prior to crush-up"? Or is that rather a collateral result?

 

[Major_Tom]

Each is given within a condensed version within the abstract at the beginning of each paper. Reading each abstract very, very carefully gives you that information.

Everything else flows from the abstract.

 

[Major_Tom]

Has Bazant ever addressed the fact that a significant part of the core remained standing after perimeter collapse?

Never. David Benson (co-author of BLGB) does (very poorly). I copied his comments on the "spire" at the end of my reviews.

My exchanges with him are available in another forum.

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


Wonderfully interesting is a collection of records which constitute the most accurate mappings of the collapses to date, available here:

3: Toward Accurate Collapse Histories

The final 3 Bazant papers were written in 2007, 2008. The bulk of the information at the link above was extracted in 2009, 2010. The comparison between Bazant claims and the mappings at the link is illuminating.

Quite primitive claims within his papers compared to what is currently available.


Like the difference between night and day.

 

[OCaptain]

In a nutshell, the original outcome was that Bazant showed that there was enough energy available for complete destruction of a tower, given a 1 storey free-fall drop at the initiation zone, and some conditions favorable for survival.

Such conditions included full buckling of every column at every storey (rather than the lesser energy requirement to break column splices every 3 storeys), the limiting case.

Much has been said and inferred beyond that simple energetics based "proof" and the authors themselves ended up applying the virtual energetics based 1D model too literraly to reality.

Bazant showed their was enough energy available.

Might be useful for you to read the following thread...
Applicability of Bazant's model to the real world

No, no! Here's Bazant in a nutshell:

"I'm Bazant, and I'm in a nutshell! How did I get into this nutshell?"

Sorry, I literally could not resist!

 

[ozeco41]

Is it so difficult to describe the premises, objects, and objectives of the 4 Bazant papers? ....

My problem is that it is all past history. To respond to your request with any precision I would need to re-examine the papers and I have never done so with the focus you suggest.

....M_T's chapter 2.6 is helpful, no doubt, but isn't very focussed in its description of the Bazant papers. Lots of mixing of description and critique,...

Yes and the usual problems of M_T's "style" of black and whiting into false globalisations... Whether his conclusions are valid or not he rarely supports them with coherent reasoned logic.

....and very much dwelling on the crush-down-crush-up topic. Is that really the main thesis of one or two of the papers - that "crush-down occurs prior to crush-up"? Or is that rather a collateral result?

"crush-down / crush-up" is certainly a suggestion which Bazant described early in his papers and put a lot of effort into sustaining as a viable hypothesis in follow up papers. Arguably it was the most important identifying feature of his series of papers.

Only two problems with that:
1) It simply does not apply to the WTC Twin Towers collapses for elementary reasons of the unique collapse mechanism; AND
2) A lot of people who are Bazant supporters have put a lot of energy into trying to twist "crush-down/crush-up" fit onto the WTC collapses. Thereby adding to the confusion OR "proving" that those like me who dare to disagree with God are wrong. Usually expressed with overtones of pity or worse



It doesn't fit to WTC collapse.

Since IMNSHO Bazant lost any legitimate connection with WTC after Bazant and Zhou I have never given much thought to his later extensions as they wandered further away from WTC - my interest has been WTC collapses not irrelevant academic exercises.

 

[LSSBB]

My problem is that it is all past history. To respond to your request with any precision I would need to re-examine the papers and I have never done so with the focus you suggest.

Yes and the usual problems of M_T's "style" of black and whiting into false globalisations... Whether his conclusions are valid or not he rarely supports them with coherent reasoned logic."crush-down / crush-up" is certainly a suggestion which Bazant described early in his papers and put a lot of effort into sustaining as a viable hypothesis in follow up papers. Arguably it was the most important identifying feature of his series of papers.

Only two problems with that:
1) It simply does not apply to the WTC Twin Towers collapses for elementary reasons of the unique collapse mechanism; AND
2) A lot of people who are Bazant supporters have put a lot of energy into trying to twist "crush-down/crush-up" fit onto the WTC collapses. Thereby adding to the confusion OR "proving" that those like me who dare to disagree with God are wrong. Usually expressed with overtones of pity or worse



It doesn't fit to WTC collapse.

Since IMNSHO Bazant lost any legitimate connection with WTC after Bazant and Zhou I have never given much thought to his later extensions as they wandered further away from WTC - my interest has been WTC collapses not irrelevant academic exercises.

As far as I can tell, of course the actual collapse mechanism, be it M_T open-floor model or Bazant crushdown or some hybrid, still doesn't prove anything regarding CD. Does it change anything going forward regarding building design, either way?

 

[ozeco41]

As far as I can tell, of course the actual collapse mechanism, be it M_T open-floor model or Bazant crushdown or some hybrid, still doesn't prove anything regarding CD....

Certainly it does nothing to support CD. The big issue of logic for all CD claims I am aware of is that they all rest on a single identified anomalous issue. That issue may or may not be true but every one of those hundreds(?) of truther single anomaly based claims is useless standing on its isolated own with no supporting context.

Those claimed anomalies then fall into two classes. The first class being claims which if true could be directly relevant - such as claims for explosions low down in the Towers. "Direct" relevance in that if there were explosions said explosions could be directly involved as a component of CD. But it is still only "could" not the "must" which truthers claim with their abysmal lack of logic.

The second class is those claims which could be of indirect relevance such as claims for thermXte at ground zero. "Indirect" in that even if there was a 100tonne stockpile on site it does not directly support CD - there is at least one big step of proof missing.

But the big issue of logic for all CD claims that I am aware of is that they have no overall hypothesis to act as context for the anomalous issue they rest on. So, using one example, even if there was thermXte on ground zero "So what?" AND even closer to the issue - even if there was proof of explosions from use of explosives at the lower levels of the towers it is still so what? but that last point would be far too subtle for the crude polarised debates we see here.

BTW the main contribution by Major_Tom was in assigning the catchy "ROOSD" acronym. I had identified and Internet forum published the mechanism back in 2006/7 but never gave it a catchy acronym. There were probably others. So M_T certainly won the battle for "brand image" in the market. And, to sectors of this forum membership, brings the model into question because the "ROOSD" acronym is associated with M_T and prevailing wisdom for many is "everything a truther says must be wrong". Hence the reason that I repeated my old "blue sky" explanation in my earlier post.

So several people must have identified the modelling and we were all working independently with no intercommunication but coming to the same description of the floor pancake mechanism. Then some of us put it into the "three mechanisms in parallel" explanation which I have used since about 2007-8 IIRC.

.... Does it change anything going forward regarding building design, either way?

I doubt it has much impact for a few reasons including:
1) Most high rise design specialists will be competent way beyond the relatively trivial level of engineering we discuss on this forum. And they will be good enough to understand the benefits and limitations of both the "mechanism" models of M_T, Ozeco/econ et al AND of the academic modelling from the Bazant school.

2) The "hybrid" concept you mentioned is relevant but not in the way you used it.

I don't think there is a valid hybrid of actual mechanism and Bazantian theory which is suitable for explaining the WTC collapses. BUT most buildings will be designed somewhere between the extreme of "tube in tube" as used at WTC and the "homogeneous elastic body" presumed by Bazant. So the "hybrid" is not about a hybrid explanation for WTC collapse. Rather it is the reality that future buildings will likely be in the middle ground between tube in tube and Bazantian presumed homogeneity. So future buildings may be sort of "hybrids" but the explanation of WTC collapses will not be an hybrid. AND

3) Anyone who is in the top bracket of building designers, who are the only ones good enough to get high rise design contracts, will be able to learn the lessons from 9/11 and apply them in a way which progresses the industry level of practice. They will be too good to rely on either Bazant or the M_T Ozeco et al group. Remember that even without 9/11 the industry sector called "high rise design" is evolutionary. As is much engineering.



PS oops. #3 is really a duplicate of #1 but leave it stand

 

[Major_Tom]

As far as I can tell, of course the actual collapse mechanism, be it M_T open-floor model or Bazant crushdown or some hybrid, still doesn't prove anything regarding CD. Does it change anything going forward regarding building design, either way?

The actual collapse mechanism is the only lens through which the collapses or the question of CD can be approached.

Maybe best to think of it as a lens through which all other collapse questions can be viewed.

It seems at this point that we all witnessed the largest chains of cascading floor collapses ever. This knowledge helps to understand what is witnessed. Without this knowledge, it is not possible to understand what was witnessed.

In so far as building design goes, it is probably best not to construct something that can result in being the largest sets of cascading floor collapses ever again.


Perhaps the OOS design is not such a great idea.
......................

From the point of view of capacity for demolition and overpressurizations witnessed, identification of the true collapse modes is also very important.

From BLGB:

According to the BLGB description, the building acts as a giant piston. This is a very primitive way to understand real world behavior.

But in reality, the collapse fronts are very visible. The ability to identify pressurization activity at the collapse fronts allows anyone who wishes to see how pressure is released throughout the building. One can easily test the giant piston idea just by looking at the actual activity at the collapse fronts and the floors just in front of the collapse fronts.

Individual isolated overpressurizations are not so easy to explain in reality. A pressurized pulse from the 88th floor during the collapse initiation sequence when initiation happens at the 98th floor is quite strange in reality.

From the point of view of vulnerability to massive cascading progressive floor collapses, nobody needs to plant bombs the length of the building to demo it. It is possible to demo the Twin Towers in a very systematic, structured way with very few devices.


So, from many points of view, identification of the true collapse modes allows one to approach all key questions in a more intelligent way.

 

[Oystein]

I understand this much so far:

[B 2001] and [BZ 2002] showed in a limiting case for a pretty generic highrise building (steel frame?) that, if some upper block were allowed to drop through the height of one floor, then impacting forces and available kinetic energy would exceed max. static capacity and energy that can be dissipated by structural elemens by an order of magnitude, even if some assumptions were geared toward maximum survivability, such as that all the vertical elements were given a chance to exert max. force upwards and simultaneously.

The following papers ... refined the modelling for a still pretty generic (steel frame?) highrise, and "discovered" the crush-down-before-crush-up meme, which unfortunately isn't applicable to the WTC.

I am still confused: What did Bazant and partners in BV, BLGB and BL think their papers were "good for"? What was their objective, who was their intended audience?
AND did they fail to meet their objectives and educate their audience?

 

[ozeco41]

The actual collapse mechanism is the only lens through which the collapses or the question of CD can be approached....

True. For any phenomenon the test is "What really happened?" Academic models are only valid as far as they accurately represent the reality they try to model. If they are not valid models then reality must over-rule. And that principle has been overlooked many times in discussion of Bazantian 9/11 collapse discussions. People have tried to force fit faulty Bazantian ideas onto the reality of WTC 9/11.

...In so far as building design goes, it is probably best not to construct something that can result in being the largest sets of cascading floor collapses ever again...

Agreed - and the proviso "largest sets" is not needed.

...Perhaps the OOS design is not such a great idea....

Maybe. The problem is how it was implemented and it may be possible to do it with greater safety. BUT I cannot see how - then I don't think I will be asked.

...From BLGB:

[qimg]http://www.sharpprintinginc.com/911/images/photoalbum/13/BLGB_fig3.png[/qimg]

That BLGB explanation is embarrassing to read.

...From the point of view of vulnerability to massive cascading progressive floor collapses, nobody needs to plant bombs the length of the building to demo it....

True - NIST was right (and Bazant) on "global collapse was inevitable"

....It is possible to demo the Twin Towers in a very systematic, structured way with very few devices....

Technically "plausible" but I doubt "possible" other than in the limited technical "how to do it" sense. Security realities mean it could not have actually happened on 9/11 and it would be highly unlikely it could be achieved in some future building without being discovered.

...So, from many points of view, identification of the true collapse modes allows one to approach all key questions in a more intelligent way.

Yes.

 

[ozeco41]

I understand this much so far:

[B 2001] and [BZ 2002] showed in a limiting case for a pretty generic highrise building (steel frame?) that, if some upper block were allowed to drop through the height of one floor, then impacting forces and available kinetic energy would exceed max. static capacity and energy that can be dissipated by structural elemens by an order of magnitude, even if some assumptions were geared toward maximum survivability, such as that all the vertical elements were given a chance to exert max. force upwards and simultaneously....

Your understanding of their position is correct AFAICS. I have serious doubts about the "one story free fall" assumption. But my doubts fall into "no man's land". They can make whatever assumptions they like provided they justify those assumptions. BUT the one storey assumption may be a valid assumption for their claimed goal of a conservative "maximum survivability" scenario - it is not a valid assumption for a real world explanation. Remember this is where Szamboti and Chandler both got their physics wrong. (it even gets me confused on occasion and I have to stop and think. )

...The following papers ... refined the modelling for a still pretty generic (steel frame?) highrise,...

Provided it acts as if one dimensional homogeneity applies. Probably a reasonable assumption for a conventional "grid of columns" structural arrangement. But who builds those these days?

... and "discovered" the crush-down-before-crush-up meme, which unfortunately isn't applicable to the WTC....

Not sure why it is "unfortunate". It doesn't apply. What is unfortunate for several years of futile 9/11 discussion is that they did not come up with a model which does apply to WTC 9/11.

...I am still confused: What did Bazant and partners in BV, BLGB and BL think their papers were "good for"? What was their objective, who was their intended audience?...

I think that is the core problem. No explicit objectives AFAICS

...AND did they fail to meet their objectives and educate their audience?

They cannot claim they did, if my memory is correct, because they defined neither.


By the way the overall conceptual problem is another example of "Cannot see the forest for trees" ("Cannot see the wood for the trees" for Aussies and Poms) OR in similar theme "When up to your arse in alligators it is easy to forget that the objective was 'drain the swamp'".

For a current living example of the same "lose the plot" phenomenon see the "WTC7 and the girder walk-off between column 79 and 44" thread. (ignore the last few pages of that thread - it has totally lost the topic in recent days - before that it had merely lost the total picture due to a focus on details. Guilt for that on both sides of the "great divide." )