Debunked: 9/11 truth experts are knowledgeable professionals and their judgments are to be trusted

Jeffrey Orling

Senior Member
Name five or six engineering professors who would be able to explain it.
Guy Nordenson comes to mind. I don't recall the names but... I attended a "AE911T" presentation at New Jersey Institute of Technology. The usual Gage dog and pony show. Didn't convince the students and 4 or 5 profs I spoke with thought it was bull pucky... including the head of the Civil Engineering department. I have two close friends who are profs / were profs at Universities and they would be able to explain it... also thought 911truth was rubbish.

I would bet that all the prof at the department of civil engineering at my alma mater CMU can explain the collapse without missing a beat.

Anyone who has any understanding of structure and awareness of the pre collapse conditions finds the collapses were inevitable.

Go ask... and convince yourself,
 

Thomas B

Active Member
I have two close friends who are profs / were profs at Universities and they would be able to explain it... also thought 911truth was rubbish.

I would bet that all the prof at the department of civil engineering at my alma mater CMU can explain the collapse without missing a beat.

Anyone who has any understanding of structure and awareness of the pre collapse conditions finds the collapses were inevitable.

Go ask... and convince yourself,
PM me. If you can put me in contact with a curently active engineering professor who is wiling to explain this in detail, step by step, and without any talk of controlled demolition, I am all ears.
 

econ41

Senior Member
I dunno, y'all. As an informed layman, I tell people that each building got destroyed by a descending debris shield that blew away everything in its path. How much detail does the general population need to know? It's like, people generally accept that an object from space did away with the dinosaurs, and they don't go asking what was the composition and altitude of the ejecta or the exact environmental conditions that followed.
And that is correct and adequate for most general enquiries. BUT misses the point here. SOME people want to know how the "descending debris" "blew everything away". Specifically:
(A) did the descending debris crush all the columns all the way down as assumed by the Bazant & Verdure CD/CU hypothesis OR

(B) did the descending debris miss the columns, fall on the floors as seen from the visualo evidence, as is implied by NIST comments and as supported by quantified assessment. (Momentum accumulation accounts for most of the "lost" 1/3rd "G" given that the progression was at about 2/3rds "G".)

The issue cannot be legitimately dismissed because SOME people "don't go asking". The question "Is it red or blue?" is not resolved by saying "People don't care!" OR even "MOST people don't care!" OR "The people who ask me are not interested!"


In this thread Thomas B legitimately asked me for comment on a Wikipadia article. I, in effect, told him "It is great for the intended audience but there is an issue of confusion" Neither you nor "we" can tell Thomas B he is not entitled to discuss the issue on the basis that a lot of other persons "don't go asking". Thomas did ask.

And, at the base level, the reality is that there are two explantions which are in direct conflict. At least one of them must be wrong. (And - at some risk of complicating the situation further >> there is a THIRD possibilty which has not been raised ... YET!) (Don't worry - it is easily dismissed once you understand which of the two is actually correct.
 
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econ41

Senior Member
It's still very close to how it happened, much closer than the CTs, and the mistakes are the result of an honest quest for knowledge.
That is exactly the situation underpinning this debate which keeps going round in circles.
The debate in academic/professional circles has gone as far as those in the formal publishing part of the professional community want to take it. Leaving an unresolved ambiguity which, so far, has not needed resolving in that community.

The anomaly came to light in the context of on-line debate with 9/11 "Truthers". And the detailed debate in THAT context has progressed further than the debate in academia. Specifically the error allegedly made by Bazant & Verdure is the same error which key "truther" spokespersons rely on. It is central to some of the major TM claims. Including T Szamboti's "Missing Jolt" paper, D Chandler's own versions of the same false explanation and some of the claims by J Cole.

Therefore debate with truthers must address the issue. The issue does not need resolving at this stage in professional debate. It does need resolving in discussions like these which address truth movement claims.
 

Jeffrey Orling

Senior Member
I think all experts who are non truthers agree that heat was the driver of the collapse... they don't agree on where the heat had the most destructive effect. or what it was ... weakening or lengthening of steel elements. It had to be both...

The only interesting discussion was the cause(s) of the "initiation"... All steel AND concrete subject to out of spec heat was effected but some elements more than others and it's essentially impossible to know what was going on.... and where.

I am not an expert and I thing the core region was where the action was. Many think it was the floor trusses....

God only knows.
 

econ41

Senior Member
But if we distinguish sharply between initiation and progression, and asked,
That is always a desirable point in explanation. In fact SOME aspects of explanation need to distingush four sub-stages of mechanism.

"If for the sake argument the top block had moved freely straight down onto the bottom section "through the height of one floor" then would/could the collapse have progressed as a series of column failures, each localized to the story immediately below the collapse front?"

would the answer here be that yes, Bazant would be right in this (impossible-to-initiate) "limit case"?
That is near enough the "Limit Case" argument from Bazant & Zhou 2001-2. The accepted answer by those who are clear it is a "limit case" is yes. (There is a proviso I'll explain later.)

Note that problems and confusions dominated the debate from 2001/2 thru to at least 2009 when persons from both sides of the debate assumed that scenario is what literally happened. And assuming that it "literally happened" is the same mistake I suggest that Bazant & Verdure made in their 2007 CD/CU hypothesis. i.e. the central issue of contention in these current discussions.

Note specifically your recognition that the scenario is "(impossible-to-initiate)". That is one of my claimed four fatal errors in the B&V CD/CU hypothesis. And 3 of the 4 are independently fatal. I'm not aware of any crane or lifting mechanism that can suspend tens of thousands of tons weight at 1300 feet above ground and 2-300 feet radius.

The "proviso". The proof of the limit case collapse being unstoppable relies on B&Z's calculation of the falling weight of the "Top Block". Szuladzinski, Szamboti and Johns paper "Some Misunderstandings Related to WTC Collapse Analysis" claims that Bazant's weight calculation was wrong - and collapse would have arrested. That claim has not been rebutted AFAIK. https://journals.sagepub.com/doi/abs/10.1260/2041-4196.4.2.117

That would go directly to the truthers' "What if we lifted the top section the height of one story with a crane and dropped it?" scenario. It would debunk their intuitions about "the path of most resistance" etc.
I think "Yes!" But I'm not clear what you are intending.
 
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econ41

Senior Member
The only interesting discussion was the cause(s) of the "initiation"... All steel AND concrete subject to out of spec heat was effected but some elements more than others and it's essentially impossible to know what was going on.... and where.
Wanna bet? Just separate the members into (a) those who can process generic argument without needing the specifics and (b) those who cannot.

Sure we will never know how many degrees C column 207 was subjected to or exactly with column failed first, second, third ....Nth

And you and I have agreed to differ on this many times over the years BUT

These are key facts:
(a) "initiation stage" allowed the "Top Block" to start moving bodily downwards;
(b) Which means that all columns had lost their abilty to support the vertical loads resulting from weight of "Top Block";
(c) Column failures occurred as a cascading sequence;
(d) which involved load redistribution;
(e) And may have involved some heat weakening:
(f) successive failures of columns to support vertical loads reached a critical point when the "surviving" columns did not have sufficient strength to support the "Top Block" which then caused failure of the "survivors". AND
(g) Top Block moved downwards. And not it did NOT "drop" - free fall -- through a magic gap as per Bazant & Zhou
THEN
(h) (this one for those who persist with misunderstanding Bazant & Zhou) EACH column which failed by overload buckling allowed that part of top block loading to "scrunch down" with the top part of buckled column moving past the bottom part. The "TOP" bit did not "drop" to impact the bottom bit.
WHICH MEANS
(i) All the top parts of broken columns were missing their bottom parts >> THAT kills Bazant & Verdure's "CD/CU" hypothesis. AND
(j) There was no way that falling bits of columns which were missing their bottom parts could by magic get back into axial aligned contact etc etc etc

AND all that can be proved by argument involving vertical vectors without need to explain the chaos caused by horizontal vectors.

AND engineers will divide sharply into those who can process the generic - non-specific - argument. And those who cannot because they cannot load the data about which column failed first etc into their FEA suite.
 

Keith Beachy

Senior Member
...

The worry I have these days is that the progression of the WTC collapses is actually not known by engineering science. (It may be known by an engaged community of enthusiasts who have been developing the ROOSD model outside the confines of "academic" engineering research.) That is, I worry that engineers, as a profession, don't understand what happened to the structures of the of Twin Towers after the collapses initiated.

I hope I'm wrong about this. If I am, there will be a handful of engineering professors who can set me straight. Who are they?
The engineering world does know why the progression of the collapse after initiated. NIST published this, and if 9/11 truth would read NIST, the collapse progression is explained. (hint, a floor in the WTC fails above 29,000,000 pounds, in general)

As seen in NIST facts, a floor in the WTC fails when over loaded past 29,000,000 pounds. This is the progression. Don't need an engineer to explain this. ROOSD is not needed, just the fact when the connections of each floor are added up, they can only hold so much. AT collapse initiation there was more mass falling than the first floor hit could hold, and the collapse could not stop. This is an engineering fact. Thus the progression of the collapse is Known, and can be seen by video.

The fact is each WTC tower floor is supported by the core and shell. Thus the collapse goes right to the ground despite the core and shell both get more robust, thicker moving to the base. Thus the core and shell can't stop the failure of floors overloaded by mass.

Even Bazant et al. know this... and also explained this engineering fact, which is also ROOSD... lol - (did you read Bazant et al. or NIST?

because the structure is a framed tube with floor beams of large spans, the impacted floors may collapse ahead of the tube, thus depriving the tube wall of its lateral support against global buckling. (from https://archive.siam.org/news/news.php?issue=0034.08 "Why Did the World Trade Center Collapse?" Oct 2001)
Floor beams of large span - is part of ROOSD, large span = Open Office... Bazant beat MT
I found 9/11 truth were using Bazant et al. as a whipping boy.

In physics we could model the top as a block, each floor destroyed by this block - and the block in reality is WTC debris. I am wondering if the people making up the false claims about 9/11 ever took physics.

Once the collapse begins, it can't stop, this was posted by NIST, seen on 9/11, and Robertson, the chief engineer for the WTC could have explain this on 9/11 (Leslie E. Robertson passed this year in Feb 2021)

https://www.nist.gov/world-trade-center-investigation/study-faqs/wtc-towers-investigation#:~:text=vertical connection capacity-,(29,000,000 pounds,-) of a floor
This fact explains why global collapse ensued... this has been posted, please read NIST, at least the facts. And read Bazant et al works, make up your own mind. But the collapse progression has been explained, Again.

Path of least resistance is electricity, not buildings falling - using "path of least resistance" nonsense, debunks 9/11 truth on the spot.

Bazant et al. papers were academic models and assumptions to explain a collapse could happen. 9/11 truth claims are not supported with evidence.
 
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econ41

Senior Member
As seen in NIST facts, a floor in the WTC fails when over loaded past 29,000,000 pounds. This is the progression. Don't need an engineer to explain this. ROOSD is not needed, just the fact when the connections of each floor are added up, they can only hold so much. AT collapse initiation there was more mass falling than the first floor hit could hold, and the collapse could not stop. This is an engineering fact. Thus the progression of the collapse is Known, and can be seen by video.
That much is true. And it is true the several times Keith Beachy repeats the same in the remainder of the post.

That much is not disputed. It is agreed. It is NOT the point of contention.

The contention is that Bazant & Verdure in their 2007 paper postulated a "Crush Down/Crush Up" hypothesis. ["CD/CU"].

And CD/CU is premised on columns crushing in axial overload i.e. columns in line taking the load of falling debris.

The NIST and similar hypotheses are premised on debris MISSING columns and landing on floors. Independent of whether or not those floors are described as "Open Office Space".

Load missing columns is inconsistent with load falling on columns. B&V is inconsistent with NIST and other hypotheses which are even more explicit than NIST.

NIST et al say "Debris weight hits floors - columns NOT in line. Bazant & Verdure say columns IN line resisting collapse.

Those two are in CONFLICT whether or not we accept Thomas B's assertions that persons, like me, posting here are not competent as experts because we are not academic professors engaged in formal publishing.

So somebody... anybody... PROVE me wrong without resorting to implicit ad-hom and I'll say "Thank you!"
 
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Mendel

Senior Member.
But "progressive failure" also involved the progression of failures laterally through the frame as failed column loads were transferred to adjacent columns and this was a progressive process... similar to how a sink hole often grows in diameter.
Also similar to the Champlain Towers South collapse initiation (although the progression there was crush-up because the failure was at the bottom).

Path of least resistance is electricity, not buildings falling - using "path of least resistance" nonsense, debunks 9/11 truth on the spot.
"Least resistance" in structures is statics: broadly simplified, the part that's overstressed the most fails first. (which is also why cars have crumple zones now.) (Also, this is knowledge hard-won by playing bridge construction games.;))

But once we go from "failing" to "falling", we no longer have a complex structure with connected elements that share and distribute stress. We just have lots of gravity and impacts. (If you hit something with a sledge hammer, it'll fail where the hammer hits.)
PM me. If you can put me in contact with a curently active engineering professor who is wiling to explain this in detail, step by step, and without any talk of controlled demolition, I am all ears.
If I was that professor, I'd ask you whether you have read and understood the NIST report before re-explaining all of that. I would also ask you to read "Why Buildings Fall Down" by Matthys Levy. (It's the sequel to "Why Buildings Stand Up".)
We've also established that understanding the wikipedia article is a good place to start. (I find that re-reading it gave me new insights.)

"Give an unpaid lecture on the WTC collapses to someone with no engineering knowledge" is not what I'd consider a polite request.
 
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Thomas B

Active Member
"Give an unpaid lecture on the WTC collapses to someone with no engineering knowledge" is not what I'd consider a polite request.
Academics consider it part of their job to answer questions from the public within their area of expertise. This "service" function is often mediated by journalism, but it can take the form of answering a mail from a private citizen. Sometimes academics even write popular books or make videos unasked to share what they know. They will often say both that they enjoy explaining things to laypeople and that it challenges them to think more clearly. So I'm not as pessimistic about this as you are. The important thing is to pick the right expert.

It is intersting, however, that the only engineers who seem willing to talk to the public about the WTC (and make long, detailed videos about what they think happened) are the truthers' "experts". There are lots of free engineering lectures online by qualified engineering professors and also some very good educational videos by professional science communicators. Some of them are about famous building collapses. If there is a solid body of engineering knowledge on the subject, there is no reason that one of these lectures or videos couldn't be about the destruction of the WTC.
 

econ41

Senior Member
They will often say both that they enjoy explaining things to laypeople and that it challenges them to think more clearly.
Those are the two main reasons I became involved in and remained in these discussions. It was a lot more rewarding back in 2007-2013. Both "sides" were learning and lots of persons wanting to understand more. Then serious interest in the engineering declined in the on-line "layperson" discussions. Academic discussion had stagnated about about 2009 or 2010. Hence much of the reason the Bazant <> NIST et al differences have not been resolved in the domain of academic/professional formal publishing.
 

Jeffrey Orling

Senior Member
So... I have read numerous books about some topic in science which interested me over the years. These topics were in fields where highly educated PhDs did research. Most work in the field of science is published... usually in professional journals... peer reviewed. Some write books and some books are targeted at the lay public. I suppose the core reason is that knowledge of science about our world is meant to be shared with humanity and publishing is the most effective way. It leaves a record and one can see how understanding evolves.. and becomes more accurate over time.
There are several scientists who write for the public (as well as for their peers). There are also some non scientist who write about science topics for the public.
Examples of writing for the public I can think of Richard Dawkins and John McPhee.
John McPhee
https://www.thriftbooks.com/a/john-...MI0ruBno2w8wIVigutBh0cEQWkEAAYAyAAEgLL9PD_BwE

Richard Dawkins
https://www.thriftbooks.com/a/richa...MIzZOu3o2w8wIVxz2tBh39ZQIQEAAYASAAEgJARfD_BwE

Both of these authors delve into science topics and present them for the lay public...Both authors are good writers. There are others who are "popular science" writers.

Scientific American is a magazine which bridges the gap, perhaps between the highly technical audience and the popular audience

And then there's Popular Science
https://en.wikipedia.org/wiki/Popular_Science

So what Thomas B is after is not something unknown. Again, I think there is popular literature about 9/11 WTC. But there has been independent "work" which can be found on 9/11 discussion forums which has not made it into a formal publication... And if one has been following the online forums it is obvious that there is no consensus on precisely what happened. There seems to be consensus that heat was the undoing... but knowing where, when, how much is not agreed upon... AND because of the complexity and lack of real time data... we may never have the precision many would like. Yet there were lessons learned by the engineering community from 9/11.

I suspect that because the online research was "free lance" and not by "established scientists" and engineers with associations to universities and so on....the work has not reached the level to interest science writers. Note that Gage tried to use the traditional approach when he went to UA and had Hulsey do his bidding.

Perhaps... and this is just a guess.... one of the least discussed aspects of the collapses was the roll the engineering designs played. Could other engineering design solutions have not collapsed? This is of course theoretical. But it does seem there should be some objective way to assess "survivability" of a high rise. It hardly matters in the WTC disaster. The buildings were sound and the failures can be attributed to out of spec conditions. Can we expect more robust strategies to resist fires than were used at the WTC? Should a "collapse arrest" feature by included?
Whether of not the floor trusses were the culprits... they continue to be used in high rise buildings.
ConEd sold the air rights and a developer erected a 40 story tower over it requiring "novel" engineering and a traditional grided bay design was not possible. But a second building was built after 7WTC collapsed. So perhaps the engineering world is comfortable with the type of engineering used at the WTC... Here's a summary of talk about this:
https://news.stanford.edu/pr/01/wtcpostmortem125.html In the article he notes that there is no consensus of which of three scenarios was correct. (maybe there were more than 3?) But his takeaway is heat from fire.

So... as far as understanding goes...one can "see" fire can destroy those buildings in multiple ways. Is that sufficient to design better buildings going forward? Isn't that the concern of the public rather than engineering esoterica?
 
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Jeffrey Orling

Senior Member
Those are the two main reasons I became involved in and remained in these discussions. It was a lot more rewarding back in 2007-2013. Both "sides" were learning and lots of persons wanting to understand more. Then serious interest in the engineering declined in the on-line "layperson" discussions. Academic discussion had stagnated about about 2009 or 2010. Hence much of the reason the Bazant <> NIST et al differences have not been resolved in the domain of academic/professional formal publishing.
What interests me now once my technical curiosity was "satisfied" (more of less) was how people responded to and reacted to the event... maybe mass psychology... hive minds and so on. It seems crazy to me that the truth movement still has legs and people can be pulled into the rabbit hole... intelligent people. I can only attribute this to a widespread distrust of authority, government and even science.... and that environment nourishes conspiracies. Religion of course is anti science and so many people have "faith" and will follow what amounts to irrationality without hesitation. You can see this in the Gage story as his anti vax beliefs got him expelled from AE911T which "pretends" to be science and engineering based. I think the origins of the truth movement was very much anti establishment anti media... But like anti vaxxers they use (junk) science to support and sell their anti authoritarian anti science beliefs.
 

econ41

Senior Member
As usual Jeffrey your architect's perspective identifies some of the engineering challenges, I'll just offer comments on a couple of them;
Perhaps... and this is just a guess.... one of the least discussed aspects of the collapses was the roll the engineering designs played. Could other engineering design solutions have not collapsed? This is of course theoretical. But it does seem there should be some objective way to assess "survivability" of a high rise. It hardly matters in the WTC disaster. The buildings were sound and the failures can be attributed to out of spec conditions. Can we expect more robust strategies to resist fires than were used at the WTC? Should a "collapse arrest" feature by included?
I suggest "ranking" those issues in "order of importance".

So the "top level issue" is that the failures were primarily due to what you call "out of spec conditions". They were not designed to withstand the fire consequences of aircraft impact. That much obvious for the Twin Towers. Not as obvious for WTC7 - we have possibly been suckered in by the truther lies about "office fires". None of the 3 towers situations involved the fires they were designed for. They were not "office fires".

Then, second I think, was the design a contributor to the collapse. Yes without doubt - a conventional "grid of columns" design would probably be more resistant to progressive collapse BUT would not have been viable for WTC Twins. Both commercially (office space limitations) and structurally (too heavy) BUT was it "contributory negligence" is a far more complex issue. Which brings in the next aspect:

Can buildings be designed to "fail safe" i.e. can they be designed to minimise both occupant risk and structural risk if they are taken traumatically well outside the design envelope. A major issue for regulatory philosophy... I wont attempt to elaborate here... the brief answer is "Yes" but there are limitations. And that leads to the next issue

Can we design buildings to withstand anything that a malicious person can throw at them. I say "Wrong question!" Rather than try to design high rises which can withstand a scale of attack higher than impact by full size full speed airliners >> the better soluntion could be to prevent such attack. << And THAT is the strategy which has been adopted. BUT with changes to the architectural aspects of design to increase redundancy of occupant escape paths and fire sprinkler plumbing.
 
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econ41

Senior Member
What interests me now once my technical curiosity was "satisfied" (more of less) was how people responded to and reacted to the event... maybe mass psychology... hive minds and so on.
As you know incident, emergency and counter-disaster management was a strong "sideline" of my career. I've been astonished at how those FDNY commanders managed to continue functioning and making the right "calls" through that incident. e.g. despite ~20 years of truther mendacity "pulling" WTC7 was the correct choice. So much for "on the day" command of response. The later political response and consequences is a far more complex discussion.
 

Jeffrey Orling

Senior Member
As you know incident, emergency and counter-disaster management was a strong "sideline" of my career. I've been astonished at how those FDNY commanders managed to continue functioning and making the right "calls" through that incident. e.g. despite ~20 years of truther mendacity "pulling" WTC7 was the correct choice. So much for "on the day" command of response. The later political response and consequences is a far more complex discussion.
I was referring to the post collapse "dialogue" and the rise of conspiracies...
 

Thomas B

Active Member
So what Thomas B is after is not something unknown.
Indeed. It is surprising (and, to some, a bit suspicious) that it doesn't yet exist.

Could other engineering design solutions have not collapsed? This is of course theoretical. But it does seem there should be some objective way to assess "survivability" of a high rise. It hardly matters in the WTC disaster. The buildings were sound and the failures can be attributed to out of spec conditions. Can we expect more robust strategies to resist fires than were used at the WTC? Should a "collapse arrest" feature by included?
This something Uwe Starossek explicitly takes up in his book, Progressive Collapse of Structures, as I recall. I don't remember what he concludes. Judging by his list of publications, he's quite the expert on progressive collapse.

The idea of "survivability" gets me thinking. One good way of explaining exactly how vulnerable the towers were to the 9/11 attacks would be to imagine a smaller, slower plane, producing less structural damage and smaller fires. What's the biggest fire the buildings could have survived? (Or, more precisely, what's the worst combination of structural damage and fire progression that the buildings could have survived?)

Similarly, one could ask whether the buildings could have survived a shorter fire (i.e., one that was put out sooner).

Finally, and I think either Starossek or Bazant (or both) mention this in passing, we could how high the planes would have had to hit for the buildings to survive.

It would be surprising if the 9/11 attacks were just exactly too much for the towers. So identifying the limit cases would be quite useful in helping us to understand how strong the buildings were and why they weren't built much stronger.

Again, this is something engineers would have done well to be talking openly about all these years. Their silence, in my opinion, left the field wide open for conspiracy theorists.
 

Mendel

Senior Member.
What's the biggest fire the buildings could have survived? (Or, more precisely, what's the worst combination of structural damage and fire progression that the buildings could have survived?)
That's not a question we can answer. What we know is what type of fire the building was designed to be protected against.


Similarly, one could ask whether the buildings could have survived a shorter fire (i.e., one that was put out sooner).
Same thing, obviously the buildings were still up after half an hour of fire, but how short exactly is not a question we can answer with the data we have.


Finally, and I think either Starossek or Bazant (or both) mention this in passing, we could how high the planes would have had to hit for the buildings to survive.
Same thing, how much weight could exactly have been dropped on a floor? You have an expectation that the means exist to answer these question, when they don't.
A small dose of respect for the very smart people who analysed the collapse, please: if these questions could have been answered, they would have been. (How is your reading of the NIST report coming along?)

So identifying the limit cases would be quite useful in helping us to understand how strong the buildings were and why they weren't built much stronger.
The opposite is true: without an understanding of how to derive these answers from the construction drawings, the questions can't be answered. And if the knowledge needs to come first, it is much easier to acquire through experiments.

It is also well known why they were not built much stronger. Building stronger than you need to costs more, so your level of strength is dictated by the engineering wisdom and building codes of the day.


Again, this is something engineers would have done well to be talking openly about all these years. Their silence,
There was no silence. Building codes were changed as a consequence of 9/11.

You are committing the conspiracy theorist's mistake of demanding answers where there are none, and of assuming that information you don't know about does not exist; and if it does, you complain that you were not told, but pretending you speak for others. In a retail context, that behaviour would get you labeled as a "Karen" customer.

(Seeing someone imply that answers should exist that shouldn't, and implying that information doesn't exist that does, produces a visceral aversion reaction for me.)
 
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Mendel

Senior Member.
P.S. There were lots of google hits on engineering lessons from 9/11, here is one:
Article:
The structural engineering profession studies events such as those of 9/11 to improve practice. Many of these studies, conducted by organizations such as the Structural Engineering Institute at the American Society of Civil Engineers (SEI/ASCE), the National Institute of Standards and Technology and the Federal Emergency Management Agency, have documented characteristics, such as redundancy and ductility, that enhance resistance to extreme assaults. Building on that information are researchers and practicing structural engineers striving to make our structures safe and economical for everyday use and also survivable when damaged.
 

Jeffrey Orling

Senior Member
All 3 collapsed totally... and all were subject to fire/heat not effectively mitigated.

7WTC was not flooded with jet fuel. There was fire fighting and sprinklers... but as a result of falling debris the water main which supplied 7WTC was destroyed and could not replenish the sprinkler system. There was also loss of power... which may have rendered the lift pumps for the sprinkler system inoperable. (don't recall what kind of sprinkler system the building had). So fires simply burned all day long once they got started. Do we know what started the fires on the NW quadrant (col 79)? Obviously without fire suppression there would be spread.
But I am curious about the amount of fuel to generate the heat to do its thing to the steel in the col 79 vicinity. How long would typical office fires burn... before they consume available fuel?
There was fuel stored in the building but not on the floor we are told where col 79 "failed" and the collapse was "initiated". This is confusing/concerning. But I suppose it unlikely that a fire would be allowed to burn that long under "normal" circumstances.
 

Thomas B

Active Member
In a retail context, that behaviour would get you labeled as a "Karen" customer.

(Seeing someone imply that answers should exist that shouldn't, and implying that information doesn't exist that does, produces a visceral aversion reaction for me.)
I'm not sure what you're trying to accomplish by insulting me. But it seems to me that you should follow your gut here and, well, avert.
 

econ41

Senior Member
I was referring to the post collapse "dialogue" and the rise of conspiracies...
Hence my reference to "The later political response and consequences is a far more complex discussion." The focus of much of the debate has been on CT aspects. And - as this thread and its previous incarnations show - there has actually been very little discusion of the collapses in the professional literature. Most professionals understand that the collapses were "progressive failures" and have little need to debate the details. The details are neded in discusion with lay persons and especially when rebutting CT claims based on misunderstanding. Hence the reason the on-line debate is both divergent and in some aspects further advanced than formal academic discussion of "papers".
 

Jeffrey Orling

Senior Member
Hence my reference to "The later political response and consequences is a far more complex discussion." The focus of much of the debate has been on CT aspects. And - as this thread and its previous incarnations show - there has actually been very little discusion of the collapses in the professional literature. Most professionals understand that the collapses were "progressive failures" and have little need to debate the details. The details are neded in discusion with lay persons and especially when rebutting CT claims based on misunderstanding. Hence the reason the on-line debate is both divergent and in some aspects further advanced than formal academic discussion of "papers".
I think the online guys such as you, femr2, Oystein etc... were more interested in the details and paid close attention to the visual record to inform their thinking.
 

econ41

Senior Member
I think the online guys such as you, femr2, Oystein etc... were more interested in the details and paid close attention to the visual record to inform their thinking.
EXACTLY. Put simply most early analysts adopted macro level simplifications and ignored the actual mechanisms of collapse.

And thereby made what should have later been recognised as two fundamental errors. This thread is actually floundering over those same two errors.

Those early analyses followed two false trails. The first was focusing on the macro motions. 'Why did progression proceed at about 2/3rds "G"?' The second was chasing "One dimensional approximations" Nobody seemed to attempt to analyse "what actually happened" i.e. tried to explain the actual collapse mechanism.

The NIST Report explicitly did NOT explain the progression stage tho - if you read NIST carefully - the principles were understood but not explicitly stated. Bazant & Zhou's limit case was a 1D approximation and the "Tube in Tube design is as far as possible from being suited to 1D approx. OK for the B&Z 2001-2 "Limit Case" even tho many got it wrong. Totally wrong when replayed in B&V 2007 as "CD/CU".

And that is the central error I identified in that Wikipedia article - Bazant & Verdure's "CD/CU" is a 1D approximation. The same error that the online debate has mostly broken out of is still reflected in the professional literature which has stagnated, And the ambiguity faithfully presented in the Wikipedia argument.
 
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Mendel

Senior Member.
I'm not sure what you're trying to accomplish by insulting me. But it seems to me that you should follow your gut here and, well, avert.
Apologies, I don't intend to insult you.
I was trying to characterize your line of discussion, not trying to say anything about you personally.
 

Jeffrey Orling

Senior Member
EXACTLY. Put simply most early analysts adopted macro level simplifications and ignored the actual mechanisms of collapse.

And thereby made what should have later been recognised as two fundamental errors. This thread is actually floundering over those same two errors.

Those early analyses followed two false trails. The first was focussing on the macro motions. 'Why did progression proceed at about 2/3rds "G"?' The second was chasing "One dimensional approximations" Nobody seemed to attempt to anlyse "what actually happend" i.e. tried to explain the actual collapse mechanism.

The NIST Report explicilty did NOT explain the progression stage tho - if you read NIST carefully - the principles were understood but not explicitly stated. Bazant & Zhou's limit case was a 1D approximation and thew "Tube in Tube design is as far as possible from being suited to 1D approx. OK for the B&Z 2001-2 "Limit Case" even tho many got it wrong. Totally wrong when replayed in B&V 2007 as "CD/CU".

And that is the central error I identified in that Wikipedia article - Bazant & Verdures "CD/CU" is a 1D approximation. The same error that the online debate has mostly broken out of is still reflected in the professional literature which has stagnated, And the ambiguity faithfully presented in the Wikipedia argument.
YOU NAILED IT! Hall of fame!
 

econ41

Senior Member
All 3 collapsed totally... and all were subject to fire/heat not effectively mitigated.
All three were subjected to fires that were bigger than specified in the design parameters. That aspect is ignored or lied about by truthers claiming "office fires". A mendacious play on words. None of them were the "office fires" the buildings were designed to withstand.
All 3 collapsed totally... and all were subject to fire/heat not effectively mitigated.

7WTC was not flooded with jet fuel. There was fire fighting and sprinklers... but as a result of falling debris the water main which supplied 7WTC was destroyed and could not replenish the sprinkler system. There was also loss of power... which may have rendered the lift pumps for the sprinkler system inoperable. (don't recall what kind of sprinkler system the building had).
Correct. The fire sprinklers had a lower floors zone supplied by mains pressure then higher level zone or zones provided with buffer storage tanks and replenished by pumping. I cannot remember more details. Of course failure of water mains meant no sprinklers to the lower zone and only minutes supply for upper zones. And the killer >> deliberate choice to not invoke the regime of "active firefighting" which would include "feet on the ground" firefighters but also booster pump replenishment of water for both sprinklers and firemen's hoses. >> and no mains electricity power available therefore replenishment would involve ad-hoc electricity supply generators >> it gets worse doesn't it?

But I am curious about the amount of fuel to generate the heat to do its thing to the steel in the col 79 vicinity. How long would typical office fires burn... before they consume available fuel?
There was fuel stored in the building but not on the floor we are told where col 79 "failed" and the collapse was "initiated". This is confusing/concerning. But I suppose it unlikely that a fire would be allowed to burn that long under "normal" circumstances.
Take care that you don't get lost in circularity chasing your tail. Remember the design includes - is premised on - the "three hour fire rating" So the "How long...?" questions are subsumed in the assumptions about "active fire fighting commenced within three hours.." (And not forgetting the PRIMARY objective of fire rating - "All occupants escaped")
 
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Jeffrey Orling

Senior Member
Take care that you don't get lost in circularity chasing your tail. Remember the design includes - is premised on - the "three hour fire rating" So the "How long...?" questions are subsumed in the assumptions about "active fire fighting commenced within three hours.." (And not forgetting the PRIMARY objective of firerating - "All occupants escaped")
I don't know how long and hot the fuel load on that floor at that location was. I know about hr ratings and the build supposedly had fires bring 6 or 7 hrs .... I don't recall... but longer than 3 hrs. So of the contents was typical and there was no sprinklers... and no active fire fighting... another building could see the same fate... at least lose a column and surrounding floor. Successful load transfer would be dependent on the steel design... beams, girders and floor plates.
 

econ41

Senior Member
I don't know how long and hot the fuel load on that floor at that location was. I know about hr ratings and the build supposedly had fires bring 6 or 7 hrs .... I don't recall... but longer than 3 hrs. So of the contents was typical and there was no sprinklers... and no active fire fighting... another building could see the same fate... at least lose a column and surrounding floor. Successful load transfer would be dependent on the steel design... beams, girders and floor plates.
Don't miss the key point. No active fire fighting and it still lasted nearly twice the fire rating. To my thinking that subsumes all the concerns about how much fuel. Again - come at it from yet another direction - if you have a building designed for active firefighting starting within three hours (MAXIMUM - probably far less) AND you deliberately leave it without either active fire fighting OR working sprinklers >> you deserve what you get. Probable collapse.

Yet another alternate "take". Of course another building would risk the same fate. It is NOT guaranteed but...

And all the details as to how it fails are not relevant to the primary question "Would it fail?"
 

Jeffrey Orling

Senior Member
Don't miss the key point. No active fire fighting and it still lasted nearly twice the fire rating. To my thinking that subsumes all the concerns about how much fuel. Again - come at it from yet another direction - if you have a building designed for active firefighting starting within three hours (MAXIMUM - probably far less) AND you deliberately leave it without either active fire fighting OR working sprinklers >> you deserve what you get. Probable collapse.

Yet another alternate "take". Of course another building would risk the same fate. It is NOT guaranteed but...

And all the details as to how it fails are not relevant to the primary question "Would it fail?"
I don't know what the 3hr rating is actually for... time to do active fire fighting? Time to evacuate? I don't think it means time to total failure...
 

econ41

Senior Member
I don't know what the 3hr rating is actually for... time to do active fire fighting? Time to evacuate? I don't think it means time to total failure...
Both those two - and the order of importance is reversed so: Time to evacuate and time to START active fire fighting.

And it is not "time to total failure". It is MINIMUM designed time. And I dont know how the "end point" is defined. I cannot see it being a binary yes<>no threshold... More realistically it would be a situation specific assessment by the firefighters - "Is it safe to keep trying" and "Can we beat it" and "How can we minimise damage". AKA a decision based on fire fighting protocols NOT pre-determined engineering theories.
 
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Mendel

Senior Member.
You almost literally said, "Your type ('Karens') make me puke ('produces a visceral reaction')."
Yeah, that's not how I wanted that to come across, sorry.
(The visceral reaction is just a strong feeling of unease in my belly, not actual puking, but it is unusual and noticeable; because you can't see that over the Internet, I verbalized it when I wouldn't in a different situation.)
 
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