OOS Collapse Propagation Model

[DGM]

I'm wondering if there would be any reason to think the fire protection in the twins was substandard in the collapse zones?

 

[WilliamSeger]

The posters here may want to read the written history of the WTC collapses a little better before producing the typical and predictable knee-jerk reactions expected within an environment like this.

Well, I've read enough written history of the WTC collapses to know that Quintiere's major beef with NIST was disagreement over their conclusion that, if not for the jet crashes removing fireproofing, the buildings would have survived. Quintiere believes the fireproofing was inherently inadequate, and although NIST found it was "to code" (despite Regenhard's implication that it wasn't), he's probably right. But that has nothing to do with this:

James Quintiere also didn't seem aware that the collapse progression mechanism some of us call 'ROOSD' existed. Neither did David Benson, co-author of BLGB. Neither did Bazant. This is a very hard pill for many people to swallow as is clearly being documented in this revealing and intriguing thread.

I refuse to believe that you don't know that the highlighted part is simply not true, since I've pasted the relevant part of BZ here several times. Your dishonesty is a very hard pill to swallow.

Friends and JREF/ISF regulars, the the written technical history of the WTC collapses is rich and fascinating..and troubling, containing many internal contradictions. Please don't trivialize it by turning it into a simplified set of memes like the refrain of a pop song.

Or, if you're going to buy into memes, be very careful who you buy them from. Some people are selling a shoddy product.

 

[WilliamSeger]

Sander - If you stop at that point you have made a reasonably clear and correct point. Structures with multiple interconnected sub-units tend to have more inbuilt redundancy than structures built with single point failure. And I'll leave that assertion of a base level engineering principle as pedantically generic as I can as a measure of defence against nit-picking. If I write it as "multiple redundancies tend to mean less prone to catastrophic single point failures" it almost goes circular. It should be bleeding obvious - more redundancy - greater separation of sub-entities SHOULD mean less prone to catastrophic global failure.

True, but with respect to the WTC, while the open office space moved columns to the perimeter, it put a lot of columns on the perimeter, which had enough redundancy to to survive the jet crashes.

 

[JSanderO]

True, but with respect to the WTC, while the open office space moved columns to the perimeter, it put a lot of columns on the perimeter, which had enough redundancy to to survive the jet crashes.

The "issue" is not whether the columns were strong enough or not... They were obviously... the building stood through several hurricanes... The issues was the structural DESIGN.

I can't imagine what sort of high rise would topple from such a plane strike. THAT is not a test of much.

Do you think the ESB would collapse from the plane strike?

Do you think it would experience a global collapse after an hr.?

 

[WilliamSeger]

The "issue" is not whether the columns were strong enough or not... They were obviously... the building stood through several hurricanes... The issues was the structural DESIGN.

But the actual issue ozeco41 raised (and the one I responded to) was about how the number of elements relate to redundancy.

I can't imagine what sort of high rise would topple from such a plane strike. THAT is not a test of much.

I dare say that many office towers wouldn't have survived the initial plane strike, and I'd put WTC7 on that list.

Do you think the ESB would collapse from the plane strike?

Do you think it would experience a global collapse after an hr.?

As I said, I don't know, but I do know that the ESB columns are encased in cinder concrete, so it had much better fireproofing. If it survived the crash, it might survive the fire, but I wouldn't try to predict either on the basis of column spacing. However, we're discussing the collapse progression here, and as I said, if several floors all started to fall, then the whole thing would go.

 

[beachnut]

... Say you have a river to cross and you need to build a bridge. You can do one large clear span or have several shorter spans... one after the other. In the first if the span drops the entire bridge is kaput. In the second case if one span fails the rest of the bridge remains and the repair is certainly not as expensive. In both cases the river crossing function has been lost. ...

DO you think the ESB would have survived such an strike?

Don't use the Golden Gate bridge? Or the Bay bridge...

ESB suffer significant damage (deaths, fire) in a very small 18 pounds of TNT KE event; fire from a small plane. The WTC would have stopped the plane at the shell.

The ESB would suffer significant damage to many steel elements since the exterior can't stop a 18 pound TNT KE aircraft impact, the WTC design for 187 pounds, stopping the aircraft at the exterior. 911 planes would have done significant damage to the ESB.

When you ask the question... fire systems, escape routes, etc; what would a 1400 and 2093 pounds of TNT KE event do to the ESB? Would it be used again after the vast multi-floor fires, and ejected material not stopped and stripped of KE by the exterior like the WTC did; how much damage would there be to the surrounding area.

"Ordinary" office fires have totaled buildings with no help from planes flying 500 mph, with 10,000 gallons of fuel starting fires in seconds. One Meridian Plaza, Windsor Building; totaled by fires not fought.
Would the ESB survive? Windsor and One Meridian were still standing; never used again.

Be sure to blame the design for the acts of murderers. When you have accidents blame it on the car, sure you were speeding, doing 65 on a 35 caution turn; but blame your car...
When did you drop CD? When did MT drop CD. Much more interesting than the NIST witch hunt BS.

 

[ozeco41]

Sander - If you stop at that point you have made a reasonably clear and correct point. Structures with multiple interconnected sub-units tend to have more inbuilt redundancy than structures built with single point failure. And I'll leave that assertion of a base level engineering principle as pedantically generic as I can as a measure of defence against nit-picking. If I write it as "multiple redundancies tend to mean less prone to catastrophic single point failures" it almost goes circular. It should be bleeding obvious - more redundancy - greater separation of sub-entities SHOULD mean less prone to catastrophic global failure.

True,

Sure - and that point was what I was reinforcing for Sander who had already correctly identified the key issue of redundancy at sub system level so that single point failure is avoided.

but with respect to the WTC, while the open office space moved columns to the perimeter, it put a lot of columns on the perimeter, which had enough redundancy to to survive the jet crashes.

Yes - that was part of my starting point for WTC but the assertion about redundancy as a protection against single point failures is a generic principle. It is not guaranteed to be globally true but I covered my arse with pedantic care - "multiple interconnected sub-units tend to have..." and "less prone to" neither of which are global guarantees but certainly "more likely than not".

The "issue" is not whether the columns were strong enough or not... They were obviously... the building stood through several hurricanes... The issues was the structural DESIGN.

Agreed and there is little difference between you and I Sander on the engineering reality that the design dominated the ultimate collapse mechanisms. The difference between us - same as it has been for several years - I do not agree with your insistence on retrospective findings of liability based on levels of CURRENT understanding which were not available when the towers were designed.

Put simply we agree on engineering we disagree on the legal and regulatory policy aspects.

 

[JSanderO]

Sure - and that point was what I was reinforcing for Sander who had already correctly identified the key issue of redundancy at sub system level so that single point failure is avoided.
Yes - that was part of my starting point for WTC but the assertion about redundancy as a protection against single point failures is a generic principle. It is not guaranteed to be globally true but I covered my arse with pedantic care - "multiple interconnected sub-units tend to have..." and "less prone to" neither of which are global guarantees but certainly "more likely than not".

Agreed and there is little difference between you and I Sander on the engineering reality that the design dominated the ultimate collapse mechanisms. The difference between us - same as it has been for several years - I do not agree with your insistence on retrospective findings of liability based on levels of CURRENT understanding which were not available when the towers were designed.

Put simply we agree on engineering we disagree on the legal and regulatory policy aspects.

I don't want to get into legal "stuff" because I am not a lawyer. And surely these sorts of construction liability law cases are complex even in a simple one. Whether there is an actionable legal case or not... is one matter... but as far as I know none of the official reports even treated those buildings as anything but off the shelf hum drum run of the mill engineering designs.... the sort millions or people live and work in. I don't think they were and the mere fact that a design is different does not mean it is inadequate. There did seem to be some code "concessions" and bending granted to PANYNJ when those buildings were built and I am not even clear about the code issues related to storing large quantities of fuel in high rise buildings.

The emergency egress was hardly robust even if it was code compliant at the time it was built.

 

[ozeco41]

I will not support you with this nonsense. Nor will I waste effort rebutting your parroting of Ms. Regenhard's emotive bigoted part truths and lies by omission.

Then why not try the written statement by James Quintiere from the same transcript of the same congressional hearing?

Same sort of reason.

You are derailing by throwing red-herrings. And you are not making a claim which I can legitimately discuss.

The posters here may want to read the written history of the WTC collapses a little better before producing the typical and predictable knee-jerk reactions expected within an environment like this.

I doubt than many posters "may want to". Try making a claim using external material as source evidence - THEN some of us "may want to read" IF we have a topic to discuss which calls on the material. If you ever do make a proper claim I may decide to respond.

James Quintiere also didn't seem aware that the collapse progression mechanism some of us call 'ROOSD' existed.

Neither did Santa Claus. So what? Whatever the value of Quintiere's narrow and specific focus it neither supports not rebuts the MECHANISM you call ROOSD not the linguistic evasions of your opponents who deny the need for and the legitimacy of the acronym "ROOSD".

Neither did David Benson, co-author of BLGB.

Stop flogging this dead horse when responding to me. Read this slowly. "I agree that Benson was wrong" - there is no point in keep putting the issue to me.

Neither did Bazant.

You are wrong BUT not as much wrong as your opponents. However both you and your opponents keep making false global assertions - you say "Neither did Bazant". They say "Bazant did describe it" or words to that effect. You are whatever 10-15% wrong they are 85% wrong. You are partly wrong because he did identify that there was a mechanism. He did not describe it and his attempts at description are more wrong than right. You opponents are wrong in several ways - the critical one being the false claim that he "described" the mechanism.

One example being this: "They" hang a lot of house of cards "logic" about the progression stage on this phrase "the failure of the connections of the floor-carrying trusses to the columns is either..." IGNORING that he is referring to the initiation stage.

This is a very hard pill for many people to swallow as is clearly being documented in this revealing and intriguing thread.

Please stop preaching to the choir. Read the thread for how many times I have invited debate of the base technical facts with little serious response. I am aware of where Bazant in B&Z was wrong and where he was right and where his supporters with 20/20 hindsight can read into his words what is not there.

Friends and JREF/ISF regulars, the the written technical history of the WTC collapses is rich and fascinating..and troubling, containing many internal contradictions. Please don't trivialize it by turning it into a simplified set of memes like the refrain of a pop song.

Then why not post some serious discussion points?

 

[ozeco41]

I don't want to get into legal "stuff" because I am not a lawyer.

Then why do you keep raising the same issues of retroactive changes in standards and resulting retrospective liability after I and others have explained the reality?

There did seem to be some code "concessions" and bending granted to PANYNJ when those buildings were built...

You should be well aware that variations from code are both routine and valid practices. By their nature most changes will be "concessions" - specific situations where the normal blanket rules are unnecessarily conservative. In my diverse career at one stage I sat for about three years in the seat where I signed off on code variations. Those were in the arena of plumbing hydraulics and my professional role was to assess the specific situation to determine if the change was safe and valid. Most were. Some I rejected.

And - not your fault Sander - but one of the dishonesties in Ms Reganhard's submission is the persistent lie by implication that "concessions" to Code are illegitimate. They are not in principle and specific examples can be professionally tested.

 

[WilliamSeger]

You are wrong BUT not as much wrong as your opponents. However both you and your opponents keep making false global assertions - you say "Neither did Bazant". They say "Bazant did describe it" or words to that effect. You are whatever 10-15% wrong they are 85% wrong. You are partly wrong because he did identify that there was a mechanism. He did not describe it and his attempts at description are more wrong than right. You opponents are wrong in several ways - the critical one being the false claim that he "described" the mechanism.

One example being this: "They" hang a lot of house of cards "logic" about the progression stage on this phrase "the failure of the connections of the floor-carrying trusses to the columns is either..." IGNORING that he is referring to the initiation stage.

Baloney.

The basic question to answer is: Can the fall of the upper part be arrested by energy dissipation during plastic buckling, which follows the initial elastic deformation? Many plastic failure mechanisms could be considered, for example: (1) the columns of the underlying floor buckle locally (Fig. 1, stage 2); (2) the floor-supporting trusses are sheared off at the connections to the framed tube and to the core columns and fall down within the tube, depriving the core columns and the framed tube of lateral support, and thus promoting buckling of the core columns and of the framed tube under vertical compression (Fig. 1, stage 4, and Fig.2(c));or (3) the upper part is partly wedged within the emptied framed tube of the lower part, pushing the walls of the framed tube apart (Fig. 1, stage 5). Although each of these mechanisms can be shown to lead to total collapse, a combination of the last two seems more realistic (the reason: multistory pieces of the framed tube, with nearly straight boundaries apparently corresponding to plastic hinge lines causing buckles on the framed tube wall, were photographed falling down, ‘‘Massive 2001’’; American 2001).

 

[JSanderO]

Baloney.

Quote is not accurate description of the event.

Where is the evidence of "sheared" truss connections?
Where is the evidence that a hollowed upper section wedged itself into the lower section?

Sure unbraced columns WITH loads will buckle. Slenderness ratio and all.

 

[JSanderO]

And - not your fault Sander - but one of the dishonesties in Ms Reganhard's submission is the persistent lie by implication that "concessions" to Code are illegitimate. They are not in principle and specific examples can be professionally tested.

Yes code concessions can occur and do occur in some cases. I don't think you should call her a liar and I do think the aggregate "code concessions" resulted in a less robust structure and pretty shabby egress and fire suppression systems... considering what turns out the be a design which rather easily can go runaway... in some catastrophe scenarios.

Maybe.

 

[Crazy Chainsaw]

Quote is not accurate description of the event.

Where is the evidence of "sheared" truss connections?

A lot of that was bolt sheer, not connections.

Where is the evidence that a hollowed upper section wedged itself into the lower section?

Banzant did not say the top block would hollow out the floor failures would occur first
Below the impact Ones.

Sure unbraced columns WITH loads will buckle. Slenderness ratio and all.

Not just that even the core columns, suffer weld damage from off center strikes.

 

[JSanderO]

A lot of that was bolt sheer, not connections.

Not just that even the core columns, suffer weld damage from off center strikes.

I saw a fair amount of bent over truss seats... did you?

 

[Crazy Chainsaw]

I saw a fair amount of bent over truss seats... did you?

Yes absolutely.

 

[Major_Tom]

Stop flogging this dead horse when responding to me. Read this slowly. "I agree that Benson was wrong" - there is no point in keep putting the issue to me.

I'm not. You are one of the only posters in this 5 year thread that can see that. Have you looked closely at the comments of other posters when these questions are put before them? Here we go again...


Hey guys, Is there anyone besides Ozeco or SanderO that can see that there is something not quite right about how David Benson, co-author of BLGB, perceived the collapse progression process of the WTC towers?

Is there anyone who can see that there is something not quite right about statements made by Bazant in the closure to BV, which is BL?



Ozeco, watch the responses. I've been asking variations of the same question for 5 years and I've always received the same responses without a single exception.

If you can see there is something not quite right about the quotes of David Benson and in the quotes produced earlier from BL but others can't, then please remember that you are the exception within the JREF/ISF environment, not the rule.

You are wrong BUT not as much wrong as your opponents. However both you and your opponents keep making false global assertions - you say "Neither did Bazant". They say "Bazant did describe it" or words to that effect. You are whatever 10-15% wrong they are 85% wrong. You are partly wrong because he did identify that there was a mechanism. He did not describe it and his attempts at description are more wrong than right. You opponents are wrong in several ways - the critical one being the false claim that he "described" the mechanism.

Ozeco, you are honest enough to admit that you have never read BV, BL, and BLGB. Many of the other posters are not but you are.

I know from some of the comments you made that you have never read them. But I'll ask anyway...did you read those papers?


If not, on what basis do you make such claims about papers you have not read?

Please stop preaching to the choir.

What choir? If you can see mistakes in BL and the Benson quotes, you are the exception to the JREF/ISF environment, not the rule. They are 'the choir', not you, and I will continue to point out their mistakes on this public forum with or without your permission to do so. That is why I reopened the thread: to record their responses just as I recorded those of David Benson.

 

[DGM]

Hey guys, Is there anyone besides Ozeco or SanderO that can see that there is something not quite right about how David Benson, co-author of BLGB, perceived the collapse progression process of the WTC towers?

Is there a reason anyone (besides you) still gives a crap? From what I see, you are the one that can't move on (and actually make a point).

Are you ready to move on?

 

[ozeco41]

One example being this: "They" hang a lot of house of cards "logic" about the progression stage on this phrase "the failure of the connections of the floor-carrying trusses to the columns is either..." IGNORING that he is referring to the initiation stage.

Baloney.

The comment was directed at M_T who has an encyclopaedic collection of misrepresentations which includes that one. If you can prove that one wrong - go for it. I'm confident M_T will get the point - and almost certainly ignore it.

Originally Posted by Bazant & Zhou 2002
The basic question to answer is: Can the fall of the upper part be arrested by energy dissipation during plastic buckling, which follows the initial elastic deformation? Many plastic failure mechanisms could be considered, for example: (1) the columns of the underlying floor buckle locally (Fig. 1, stage 2); (2) the floor-supporting trusses are sheared off at the connections to the framed tube and to the core columns and fall down within the tube, depriving the core columns and the framed tube of lateral support, and thus promoting buckling of the core columns and of the framed tube under vertical compression (Fig. 1, stage 4, and Fig.2(c));or (3) the upper part is partly wedged within the emptied framed tube of the lower part, pushing the walls of the framed tube apart (Fig. 1, stage 5). Although each of these mechanisms can be shown to lead to total collapse, a combination of the last two seems more realistic (the reason: multistory pieces of the framed tube, with nearly straight boundaries apparently corresponding to plastic hinge lines causing buckles on the framed tube wall, were photographed falling down, ‘‘Massive 2001’’; American 2001).

Never any doubt that he identified the mechanism (a) as "complicated" and (b) partly described it as one probable option. What are you disagreeing with the 85%

What are you bidding? 50-50? 85-15 the other way?

Remember the point - both sides making global claims.

Face it. B&Z was a good analysis for 9/13. It wasn't perfect. Claims that it was totally wrong are false. And claims that it was perfectly right OR - more often - claims that read more into it than it actually says are also false. The real need is to determine which bits were right AND to what extent they are relevant today including to what extent the errors flow over to OR are made in those later papers. It is easy to quote mine bits to suit either way argument. The confusions or limits on what it actually says are more evident in reading the full context of B&Z.

And I've got as much agreement as I'm likely to get on those base bits of technical fact:

(Oystein's re-numbered list - and call the "Facts" hypotheses if you prefer - they are issues of fact which have the status of hypothesis agreed between a few members "en bloc" and most of them individually agreed by many members in scattered piece meal references.)

As for ozeco's facts and procedural rules:

Fact #1a Bazant in B&Z identified that the real collapse mechanism was complicated and chose a simpler model which was valid for a "limit case argument";

Fact #1b Bazant in B&Z clearly distinguished the two different mechanisms - the more complicated real event and the simpler version supporting a "limit case" argument;

Fact #1c Bazant's "limit case" argument was conceptually valid, it has not been successfully challenged and he did not confuse the two mechanisms.

Procedural Rule #2 Discussion of WTC collapses should not use or rely on confusion of any issues of fact including the facts derived from Bazant's work.

Fact #3 The progression collapse stage for WTC1 and WTC2 was dominated by a mechanism in which material falling down the office space tube stripped floors leaving perimeter columns to fall away.

Fact #4 The real event collapse is a different mechanism to the column crushing model of the limit case argument.

Procedural Rule #5 Arguments should not be confused over the two mechanisms and any relationship they may have.

Fact #6 The later papers by Bazant et al are wrong if and whenever they apply 1D simplification models to the WTC real event".​

What I colored red is numbers I changed or added. I propose to use these for the sake of clarity and continuity.

My only reason for pursuing those recent comments is to call on both sides to stop the false global claims - no matter what the distribution of errors between the "sides".

Personally I'm quite prepared to once again withdraw from circling discussions and simply rebut any errors - by either "side" - if and when they appear in ongoing discussion which interests me.

 

[WilliamSeger]

Quote is not accurate description of the event.

Where is the evidence of "sheared" truss connections?

Here:

Above the aircraft impact floors, the failure modes were randomly distributed. However, over 90 percent of floor truss connections at or below the impact floors of both buildings were either bent downwards or completely sheared from the exterior wall suggesting progressive overloading of the floors below the impact zone following collapse initiation of the towers.

http://www.nist.gov/manuscript-publication-search.cfm?pub_id=853462

.

Where is the evidence that a hollowed upper section wedged itself into the lower section?

It was, "the upper part is partly wedged within the emptied framed tube of the lower part," and Bazant gave his reason in the quote, but that seems to be pretty much the same thing you've been talking about.