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Discussion NOT Debate Topic #1 CD/CU

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Discussion NOT Debate Topic #1 CD/CU

Postby ozeco41 » Wed Jan 04, 2017 4:11 am

WORK IN PROGRESS

The THESIS for this first discussion is:

"Bazant&Verdure's 2007 CD/CU Mechanism Does Not Apply to WTC Twins"


Background to Topic And Process.

The intended process is one of value adding discussion with a goal of achieving an agreed po0sition that participants share.

It is one of the "Limits of Bazant's Validity" issues severally identified by me and Major Tom at least as far back as 2010. It is disputed by some JREF claque members - the most recent vehement opponent being tfk in a personal attack bit of debating trickery directed at ozeco41.

WORK IN PROGRESS

Starting Point Facts for Agreement or Improvement
These are the key and necessary facts:
1) The collapse progression of the WTC Twin Towers was driven by a process which has been labelled ROOSD ["Runaway Open Office Space Destruction"];
2) Bazant & Zhou in a 2001-2 paper identified an abstract model "Limit Case" - a worst case for collapse or best case for survival based on two premises viz that the Top Block dropped one storey and impacted with full column alignment thereby putting the full designed strength of the columns in line resisting collapse;
3) The "real event" collapse model was by "ROOSD" which did not have columns in line and the main resistance to collapse in the OOS was shearing of the floor joist to column connectors;
4) Failure in the core region - tho not in the "OOS" - was by beam shear off therefore analogous to ROOSD;
5) Bazant and Verdure in their 2007 paper introduced the concept of "crush down crush up" (may need more explanation);
6) The key feature being that it assumes columns fully in line resisting arrest;
7) They postulate that this was what happened at the WTC "Twins". This issue of fact has been controversial in internet discussions;
8 ) From that premise they reason from an energy basis that the towers collapse would see the Top Block remaining intact - crushing the Lower Tower down to ground level THEN the Top Block crushing UP from below at (near) ground level.

Facts opposing this argument of B&V are:
9) The WTC Twins collapses progression was not by column crushing Rather by ROOSD for the OOS section and by analogous process for the core; << That one alone should be fatal.
10) Visual record of the start of collapse shown that columns were not in line. (Achimspok's graphic "proves" the columns missing for two sides of WTC2. It has been demonstrated by reasoned argument that the columns missed. And the factors in Achimspok's video apply for the other six sides tho not as dramatic as the large tilt of WTC2 shows,
11) It is arguably not possible to set up Top Block impacting on columns even in a demonstration experimental set-up;

Contextual Issues
12) Bazant is on record as moving to develop a generic model f which WTC Twin Towers would be a paradigm.
13) preliminary discussions have been held on how the B&V cu/cd could be modified to include a range of column space/OOS paradigms.

WORK IN PROGRESS
I'll pause there for preliminary comments on either Topic or process..

The objective is decide and agree what is correct NOT prove ozeco wrong. :wink: :)

Process suggestion - although we have long term editing on this forum for this thread I suggest that each post be left unedited after comments are received - leave a "map" of any evolution.
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Re: Discussion NOT Debate Topic #1 CD/CU

Postby Chainsaw » Wed Jan 04, 2017 12:27 pm

ozeco41 wrote:WORK IN PROGRESS
OWE - I think this is appropriate in this section of the forum - your call.
The process intent is a deliberate shift to collaborative exploration AWAY from the combative setting of antagonistic debate.


The THESIS for this first discussion is:

"Bazant&Verdure's 2007 CD/CU Mechanism Does Not Apply to WTC Twins"


Background to Topic And Process.

The intended process is one of value adding discussion with a goal of achieving an agreed po0sition that participants share.

It is one of the "Limits of Bazant's Validity" issues severally identified by me and Major Tom at least as far back as 2010. It is disputed by some JREF claque members - the most recent vehement opponent being tfk in a personal attack bit of debating trickery directed at ozeco41.

WORK IN PROGRESS

Starting Point Facts for Agreement or Improvement
These are the key and necessary facts:
1) The collapse progression of the WTC Twin Towers was driven by a process which has been labelled ROOSD ["Runaway Open Office Space Destruction"];
2) Bazant & Zhou in a 2001-2 paper identified an abstract model "Limit Case" - a worst case for collapse or best case for survival based on two premises viz that the Top Block dropped one storey and impacted with full column alignment thereby putting the full designed strength of the columns in line resisting collapse;
3) The "real event" collapse model was by "ROOSD" which did not have columns in line and the main resistance to collapse in the OOS was shearing of the floor joist to column connectors;
4) Failure in the core region - tho not in the "OOS" - was by beam shear off therefore analogous to ROOSD;
5) Bazant and Verdure in their 2007 paper introduced the concept of "crush down crush up" (may need more explanation);
6) The key feature being that it assumes columns fully in line resisting arrest;
7) They postulate that this was what happened at the WTC "Twins". This issue of fact has been controversial in internet discussions;
8 ) From that premise they reason from an energy basis that the towers collapse would see the Top Block remaining intact - crushing the Lower Tower down to ground level THEN the Top Block crushing UP from below at (near) ground level.

Facts opposing this argument of B&V are:
9) The WTC Twins collapses progression was not by column crushing Rather by ROOSD for the OOS section and by analogous process for the core; << That one alone should be fatal.
10) Visual record of the start of collapse shown that columns were not in line. (Achimspok's graphic "proves" the columns missing for two sides of WTC2. It has been demonstrated by reasoned argument that the columns missed. And the factors in Achimspok's video apply for the other six sides tho not as dramatic as the large tilt of WTC2 shows,
11) It is arguably not possible to set up Top Block impacting on columns even in a demonstration experimental set-up;

Contextual Issues
12) Bazant is on record as moving to develop a generic model f which WTC Twin Towers would be a paradigm.
13) preliminary discussions have been held on how the B&V cu/cd could be modified to include a range of column space/OOS paradigms.

WORK IN PROGRESS
I'll pause there for preliminary comments on either Topic or process..

The objective is decide and agree what is correct NOT prove ozeco wrong. :wink: :)

Process suggestion - although we have long term editing on this forum for this thread I suggest that each post be left unedited after comments are received - leave a "map" of any evolution.


Banzant s original paper, was a speculation based on his work though investigation of actual collapses.
There were certain mistakes in the paper of an academic Nature.
Subsequent papers continued those mistakes.
Tony S. Correctly Identified those mistakes but instead of viewing them as Academic he launched into a campaign of implied false malfeasance, without grounds.
We must view this from a scientific view point without false claims if we are to progress.
More comments later.
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Re: Discussion NOT Debate Topic #1 CD/CU

Postby DGM » Wed Jan 04, 2017 10:51 pm

This discussion will be of some interest to me mostly because I never really had much interest in the Bazant papers.

That said, the outline looks like a solid starting point. I may become more active when we get to the "Contextual Issues" as I've always viewed these papers in a more conceptual light and not necessarily consistent with reality.
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Re: Discussion NOT Debate Topic #1 CD/CU

Postby ozeco41 » Thu Jan 05, 2017 1:48 am

DGM wrote:This discussion will be of some interest to me mostly because I never really had much interest in the Bazant papers.

That said, the outline looks like a solid starting point. I may become more active when we get to the "Contextual Issues" as I've always viewed these papers in a more conceptual light and not necessarily consistent with reality.

OK - now for the objective of this thread I suggest we keep clear focus.

My OP statement thesis is "Bazant&Verdure's 2007 CD/CU Mechanism Does Not Apply to WTC Twins"

Your interest DGM - put simply - I think goes to "can it be fixed?" or "Could it be made to work?"

Am I reading you correctly?

If so it is a second topic and I've posted suggestions on that many years ago PLUS OWE has commented "off the top of his head" and at some length in another thread.

Let's treat them as two distinct and separate topics because they are. So

Topic #1 - Do you - do "we" - agree "Bazant&Verdure's 2007 CD/CU Mechanism Does Not Apply to WTC Twins"? THEN

Topic #2 - "Can it be made to work?"

Do you agree Topic #1 Theme or are there any bits where you need clarification OR can suggest aspects that I may have missed in that first draft?

If we get little interest in Topic #1 I will put it on the back burner and start Topic #2
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Re: Discussion NOT Debate Topic #1 CD/CU

Postby DGM » Thu Jan 05, 2017 9:46 pm

Topic#1:
I don't think BV 07 CD/CU mechanism is a good fit for the towers at all.

Topic#2:
This starts my interest in the subject. I would add "Can it be made to work and what are it's implications outside of the WTC setting?" .

This probably is too broad of a scope but it does represent my interest in the subject.

I'm going to apologize in advance if I can't respond in kind to your questions promptly. I came back from a great two week holiday break to find more jobs then I got time for. I guess that's actually a good thing......This is one of those times I wish I was 20 and just starting out. :)
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Re: Discussion NOT Debate Topic #1 CD/CU

Postby ozeco41 » Thu Jan 05, 2017 10:10 pm

DGM wrote:Topic#1:
I don't think BV 07 CD/CU mechanism is a good fit for the towers at all.

Topic#2:
This starts my interest in the subject. I would add "Can it be made to work and what are it's implications outside of the WTC setting?" .

This probably is too broad of a scope but it does represent my interest in the subject.

I'm going to apologize in advance if I can't respond in kind to your questions promptly. I came back from a great two week holiday break to find more jobs then I got time for. I guess that's actually a good thing......This is one of those times I wish I was 20 and just starting out. :)

No problem - I'm close to dropping my activity/interest in forums given the near universal shift to trivia. (I have been active on facebook - recycling 10 year old WTC canards. No brain activity needed. And I blame Oystein for getting me their and my own idiocy for staying..... :roll:

Yes we agree the two Topics. IMO #2 requires understanding of why #1 is wrong - why CD/CU doesn't apply.

For #2 "How can we make it work?" The need is to replace the energy component of the B&V maths. Currently it is the energy for crushing columns - which did not happen at wtc. Where the energy was near enough solely floor joist shearing in the OOS and horizontal beam shearing in the core. (Yes OWE I know but I'm keeping it simple till we outline the problem. )

So the need is to replace the crushing energy with energy that changes to shearing energy as the column grid spacing widens. And that involves mixing aspects that are discontinuous. And at this stage I haven't a clue what I'm bleeding talking about, :oops: As the answer - I'm at the start of framing the question. Starting to think about framing the question. :lol:
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Re: Discussion NOT Debate Topic #1 CD/CU

Postby DGM » Thu Jan 05, 2017 10:21 pm

Topic #2 likely falls outside of my level of engineering abilities (seeing I'm not one). :roll:

I'd go with a good discussion of why it wasn't a good fit. :wink:
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Re: Discussion NOT Debate Topic #1 CD/CU

Postby ozeco41 » Fri Jan 06, 2017 3:42 am

DGM wrote:Topic #2 likely falls outside of my level of engineering abilities (seeing I'm not one). :roll:
It will make me think...
....carefully. :roll:

DGM wrote:I'd go with a good discussion of why it wasn't a good fit. :wink:

I'll think about how we do it. Maybe if I take the "why nots" point by point.
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Re: Discussion NOT Debate Topic #1 CD/CU

Postby Oystein » Sat Jan 07, 2017 9:57 pm

ozeco41 wrote:...
Starting Point Facts for Agreement or Improvement
These are the key and necessary facts:
1) The collapse progression of the WTC Twin Towers was driven by a process which has been labelled ROOSD ["Runaway Open Office Space Destruction"];
2) Bazant & Zhou in a 2001-2 paper identified an abstract model "Limit Case" - a worst case for collapse or best case for survival based on two premises viz that the Top Block dropped one storey and impacted with full column alignment thereby putting the full designed strength of the columns in line resisting collapse;
3) The "real event" collapse model was by "ROOSD" which did not have columns in line and the main resistance to collapse in the OOS was shearing of the floor joist to column connectors;
4) Failure in the core region - tho not in the "OOS" - was by beam shear off therefore analogous to ROOSD;
5) Bazant and Verdure in their 2007 paper introduced the concept of "crush down crush up" (may need more explanation);
6) The key feature being that it assumes columns fully in line resisting arrest;
7) They postulate that this was what happened at the WTC "Twins". This issue of fact has been controversial in internet discussions;
8 ) From that premise they reason from an energy basis that the towers collapse would see the Top Block remaining intact - crushing the Lower Tower down to ground level THEN the Top Block crushing UP from below at (near) ground level.

Facts opposing this argument of B&V are:
9) The WTC Twins collapses progression was not by column crushing Rather by ROOSD for the OOS section and by analogous process for the core; << That one alone should be fatal.
10) Visual record of the start of collapse shown that columns were not in line. (Achimspok's graphic "proves" the columns missing for two sides of WTC2. It has been demonstrated by reasoned argument that the columns missed. And the factors in Achimspok's video apply for the other six sides tho not as dramatic as the large tilt of WTC2 shows,
11) It is arguably not possible to set up Top Block impacting on columns even in a demonstration experimental set-up;

Contextual Issues
12) Bazant is on record as moving to develop a generic model f which WTC Twin Towers would be a paradigm.
13) preliminary discussions have been held on how the B&V cu/cd could be modified to include a range of column space/OOS paradigms.

WORK IN PROGRESS
I'll pause there for preliminary comments on either Topic or process..
...

Allow me to comment on your Starting point facts:

Drop 1), for it is contained in 3).

I am not sure of 6). While it is true that B&V focus on column crushing, they note - even if in passing - that their model is amenable to other collapse mechanisms. One example is cited: The floor-slabs impacting floor slabs at Ronan Point - what we call "ROOSD".

8 ) For the same reason I doubt that "column crushing" is a necessary condition for the B&V cd/cu model to hold true. Column crushing resluts in certain kinds of crushing force functions, as displayed in Fig. 4, but it seems to me that other crushing force functions, such as those arising from a ROOSD style collapse, could be substituted. I understand B&V's conclusions such that any crushing force functions would lead to cd/cu, provided the "collapse progression criterion" is fulfilled ("If the total internal energy loss during the crushing of one story representing the energy dissipated by the complete crushing and compaction of one story, minus the loss of gravity potential during the crushing of that story exceeds the kinetic energy impacted to that story, collapse will continue to the next story. This is the criterion of progressive collapse trigger [Eq. 5]")


However, I fail to understand the relevance of the topic. It's pretty much a "So what?" to me. Suppose you disprove that CD/CU applies to the twins. Then what?


(I have a hunch that CD/CU fails to apply, but for a different reason: Another premise that B&V list is "Thus it appears reasonable to make four simplifying hypotheses: [...] 4 The stories are so numerous, and the collapse front traverses so many stories, that a continuum smearing i.e., homogenization gives a sufficiently accurate overall picture." (page 312; note the other three assumptions as well!). The observable floors are not very numerous before all is obscured by dust. They might suffice if column crushing were indeed the main collapse mode, for the crushing force functions in that case are spread out over a significant portion of a story height. Floor slab crushing each other, however, or wall panels shearing floor connections, are punctuated events, with much of the energy being absorbed within a couple of inches. B&V allow for some CU during CD: "A front propagating intermittently up and down would nevertheless be found possible if Fc(z) were considered to be a random autocorrelated field. In that case, short intervals t may exist in which the difference Fc1−Fc2 of random Fc values at the bottom and top of crushed Block B would exceed the right-hand side of Eq. 10. During those short intervals, crush-up would occur instead of crush-down, more frequently for a larger coefficient of variation.". I cannot really fathom this, so again: It is only a hunch; but I think the puctuated nature of the ROOSD process might provide for the conditions for intermittent CU&CD)
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Re: Discussion NOT Debate Topic #1 CD/CU

Postby Chainsaw » Sat Jan 07, 2017 11:50 pm

OWE, did you save the part of physorg where DBB found the Monrue's equation for a pinned beam?

I have something to explain it would be handy to have it.
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Re: Discussion NOT Debate Topic #1 CD/CU

Postby Chainsaw » Sun Jan 08, 2017 1:01 am

Oystein wrote:
ozeco41 wrote:...
Starting Point Facts for Agreement or Improvement
These are the key and necessary facts:
1) The collapse progression of the WTC Twin Towers was driven by a process which has been labelled ROOSD ["Runaway Open Office Space Destruction"];
2) Bazant & Zhou in a 2001-2 paper identified an abstract model "Limit Case" - a worst case for collapse or best case for survival based on two premises viz that the Top Block dropped one storey and impacted with full column alignment thereby putting the full designed strength of the columns in line resisting collapse;
3) The "real event" collapse model was by "ROOSD" which did not have columns in line and the main resistance to collapse in the OOS was shearing of the floor joist to column connectors;
4) Failure in the core region - tho not in the "OOS" - was by beam shear off therefore analogous to ROOSD;
5) Bazant and Verdure in their 2007 paper introduced the concept of "crush down crush up" (may need more explanation);
6) The key feature being that it assumes columns fully in line resisting arrest;
7) They postulate that this was what happened at the WTC "Twins". This issue of fact has been controversial in internet discussions;
8 ) From that premise they reason from an energy basis that the towers collapse would see the Top Block remaining intact - crushing the Lower Tower down to ground level THEN the Top Block crushing UP from below at (near) ground level.

Facts opposing this argument of B&V are:
9) The WTC Twins collapses progression was not by column crushing Rather by ROOSD for the OOS section and by analogous process for the core; << That one alone should be fatal.
10) Visual record of the start of collapse shown that columns were not in line. (Achimspok's graphic "proves" the columns missing for two sides of WTC2. It has been demonstrated by reasoned argument that the columns missed. And the factors in Achimspok's video apply for the other six sides tho not as dramatic as the large tilt of WTC2 shows,
11) It is arguably not possible to set up Top Block impacting on columns even in a demonstration experimental set-up;

Contextual Issues
12) Bazant is on record as moving to develop a generic model f which WTC Twin Towers would be a paradigm.
13) preliminary discussions have been held on how the B&V cu/cd could be modified to include a range of column space/OOS paradigms.

WORK IN PROGRESS
I'll pause there for preliminary comments on either Topic or process..
...

Allow me to comment on your Starting point facts:

Drop 1), for it is contained in 3).

I am not sure of 6). While it is true that B&V focus on column crushing, they note - even if in passing - that their model is amenable to other collapse mechanisms. One example is cited: The floor-slabs impacting floor slabs at Ronan Point - what we call "ROOSD".

8 ) For the same reason I doubt that "column crushing" is a necessary condition for the B&V cd/cu model to hold true. Column crushing resluts in certain kinds of crushing force functions, as displayed in Fig. 4, but it seems to me that other crushing force functions, such as those arising from a ROOSD style collapse, could be substituted. I understand B&V's conclusions such that any crushing force functions would lead to cd/cu, provided the "collapse progression criterion" is fulfilled ("If the total internal energy loss during the crushing of one story representing the energy dissipated by the complete crushing and compaction of one story, minus the loss of gravity potential during the crushing of that story exceeds the kinetic energy impacted to that story, collapse will continue to the next story. This is the criterion of progressive collapse trigger [Eq. 5]")


However, I fail to understand the relevance of the topic. It's pretty much a "So what?" to me. Suppose you disprove that CD/CU applies to the twins. Then what?


(I have a hunch that CD/CU fails to apply, but for a different reason: Another premise that B&V list is "Thus it appears reasonable to make four simplifying hypotheses: [...] 4 The stories are so numerous, and the collapse front traverses so many stories, that a continuum smearing i.e., homogenization gives a sufficiently accurate overall picture." (page 312; note the other three assumptions as well!). The observable floors are not very numerous before all is obscured by dust. They might suffice if column crushing were indeed the main collapse mode, for the crushing force functions in that case are spread out over a significant portion of a story height. Floor slab crushing each other, however, or wall panels shearing floor connections, are punctuated events, with much of the energy being absorbed within a couple of inches. B&V allow for some CU during CD: "A front propagating intermittently up and down would nevertheless be found possible if Fc(z) were considered to be a random autocorrelated field. In that case, short intervals t may exist in which the difference Fc1−Fc2 of random Fc values at the bottom and top of crushed Block B would exceed the right-hand side of Eq. 10. During those short intervals, crush-up would occur instead of crush-down, more frequently for a larger coefficient of variation.". I cannot really fathom this, so again: It is only a hunch; but I think the puctuated nature of the ROOSD process might provide for the conditions for intermittent CU&CD)


Oystein gases are compressible, solids and liquids are not the first steep in determination of what is valid is separating the crushing effects of solids from the expulsions of compressed gas.
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Re: Discussion NOT Debate Topic #1 CD/CU

Postby Oystein » Sun Jan 08, 2017 1:45 pm

Chainsaw wrote:Oystein gases are compressible, solids and liquids are not the first steep in determination of what is valid is separating the crushing effects of solids from the expulsions of compressed gas.

Right. This is one of the key reasons why I feel that the puncuated nature, and resulting highly peaked force functions of ROOSD impacts would tend to frustrate Bazant's attempt at formulating a continuous model - why his model, and its "cd before cu" conlusion, does not capture ROOSD well.
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Re: Discussion NOT Debate Topic #1 CD/CU

Postby Chainsaw » Sun Jan 08, 2017 1:58 pm

Oystein wrote:
Chainsaw wrote:Oystein gases are compressible, solids and liquids are not the first steep in determination of what is valid is separating the crushing effects of solids from the expulsions of compressed gas.

Right. This is one of the key reasons why I feel that the puncuated nature, and resulting highly peaked force functions of ROOSD impacts would tend to frustrate Bazant's attempt at formulating a continuous model - why his model, and its "cd before cu" conlusion, does not capture ROOSD well.


True DBB had the physics equations from Monrue, but they were incorrectly applied in a false crush down crush up, that was merely a simplification, to illustrate the lack of shed mass.
In truth it was the funnel effect of the perimeter wall, and the stabbing action of the fractured column ends that prevented mass shedding.
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Re: Discussion NOT Debate Topic #1 CD/CU

Postby OneWhiteEye » Sun Jan 08, 2017 9:43 pm

Chainsaw wrote:OWE, did you save the part of physorg where DBB found the Monrue's equation for a pinned beam?

Not sure. I have to dig up those archives and search.

One place which may have a copy of everything is Lo-Fi boards. Their robots indexed the entire set of three threads, as best as I can tell. I'll let you know.
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Re: Discussion NOT Debate Topic #1 CD/CU

Postby Chainsaw » Mon Jan 09, 2017 12:36 am

Thank you OWE.
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