What's the best popular account of the WTC collapses?

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deirdre

Senior Member.
There's some very interesting stuff (to me) going on in the final minutes. "The efficiency of the design meant that with any major element removed the whole structure would fall." That's a strong statement and probably depends on what we mean by "major". Was the removal of the lateral support provided by a single floor "major" enough, for example? One would in any case want to explain why only the most extreme circumstances (airplane impact) could eventually remove such an element. Working through this for about 10 minutes with up-to-date modeling would be great.

I do think the technical threads on MB and other forums should be edited of noise and easier to find for newbies, but this paragraph demonstrates why i personally dont think what you are asking for would be "useful" by your criteria. I, as a normal person layman who might read the book or watch the video, think that section is fine. I get the scientific concept he is demonstrating and i dont want to watch an additional 10 mins on it. That level of explanation would turn me off to the cd conspiracy theories.

It seems to me what you are asking for in this thread, would be an extremely limited audience. You are essentially wiping out both ends of the reading or watching spectrum... the guys who want detail and minor questions like yours answered in depth on one end of the spectrum, and the general public who might read a simple overview book but would be turned off by too much detail.

To me you basically want something between the NIST report and the FAQ "for dummies" version NIST put out. ("for dummies" isnt an insult, it's a writing style where they take complicated subjects and try to write it in language people can understand without the benefit of a Professor on hand to help them when they are unsure of a section or idea). <i'm only using NIST here as an example, because they have a complicated version and an easy version. i know you dont trust them and some members disagree with some of their stuff
 

Jeffrey Orling

Senior Member
I do think the technical threads on MB and other forums should be edited of noise and easier to find for newbies, but this paragraph demonstrates why i personally dont think what you are asking for would be "useful" by your criteria. I, as a normal person layman who might read the book or watch the video, think that section is fine. I get the scientific concept he is demonstrating and i dont want to watch an additional 10 mins on it. That level of explanation would turn me off to the cd conspiracy theories.

It seems to me what you are asking for in this thread, would be an extremely limited audience. You are essentially wiping out both ends of the reading or watching spectrum... the guys who want detail and minor questions like yours answered in depth on one end of the spectrum, and the general public who might read a simple overview book but would be turned off by too much detail.

To me you basically want something between the NIST report and the FAQ "for dummies" version NIST put out. ("for dummies" isnt an insult, it's a writing style where they take complicated subjects and try to write it in language people can understand without the benefit of a Professor on hand to help them when they are unsure of a section or idea). <i'm only using NIST here as an example, because they have a complicated version and an easy version. i know you dont trust them and some members disagree with some of their stuff
Perhaps one (the main??) reason Thomas has this request is that the reality is that there has not been a consensus about the collapses AND the details of those collapses. YES NIST published a lengthy report of their research and did publish a FAQ. And one perhaps could assume that this is the OFFICIAL EXPLANATION. However as noted in this thread and elsewhere nowhere does NIST describe the details of the "global collapse" which I would assert definitely seems to be difficult for lay persons to understand.
Further as has been noted in this thread... there is no consensus about the INITIATION processes... NIST maintains the floor trusses' failure "led" the collapse... ie was the "initiation" cause. Yet there are qualified engineers who assert different mechanisms in play. Or as I say... the jury is still out on this.

Long story short... You can't write the "WTC collapses for Dummies" because the LONG FORM book has not been written... one that has broad acceptance in the engineering community. YES there is consensus on ASPECTS of the collapse... such as the main driver was fire. But how and where the fire was doing the damage to lead to the collapse is not known with certainty... and it would be an unproven "theory".
 

Thomas B

Active Member
the LONG FORM book has not been written... one that has broad acceptance in the engineering community.
I don't know enough about the discipline to be sure, but this is also my impression from searching the literature. Not only isn't there a mainstream book, there isn't a review article on the collapses in any of the major journals. There doesn't seem to be a "received view" about the collapses in the engineering profession. Science journalists should find this fact in itself interesting enough to explore.
 

Jeffrey Orling

Senior Member
I don't know enough about the discipline to be sure, but this is also my impression from searching the literature. Not only isn't there a mainstream book, there isn't a review article on the collapses in any of the major journals. There doesn't seem to be a "received view" about the collapses in the engineering profession. Science journalists should find this fact in itself interesting enough to explore.
The collapses are not technical mysteries.
The mystery is the "path" that the runaway process took.
All the applicable science/engineering is settled long ago:
physical performance of building materials
Statics - Branch of mechanics concerned with balance of forces in non moving systems
laws of motion (Newton)
chemical engineering
effects of heat/temperature of building materials'

There were articles and presentations like PBS and Popular Mechanics... and Perdue's work. All made sense but there was never a detailed consensus which set for all the details.... but as there were no mysteries.... no one... or not enough people seemed unsatisfied to demand more.

This is MY opinion of the matter. The public believes the engineers can explain it and it was NOT a controlled demolition... The whole thing was set in place by crazy terrorists.... moving forward.... prevent terrorism and provide better emergency egress for tall buildings.
 
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Mendel

Senior Member.
Science journalists should find this fact in itself interesting enough to explore.
No, they "should" not. Any theory about a physical process is validated through observation; that's what I am referring to when I talk about "data". We don't have enough data on the collapse that happened to distinguish between the hypotheses on how the collapse took place. Therefore, there can't be an "authoritative" account of the collapse. (And then there can't be a popular simplification and explanation of it.)

You are putting up expectations that have no basis. Mysteries happen all the time. (Where is flight MH370?) The fact that there is no accepted theory of how the WTC went down doesn't mean there's a cover-up. For most people, it is enough to know why the WTC collapsed,and that there are possible explanations that show how it could have happened, even if we can't decide which of these is the correct one.

In fact, that's typically how Conspiracy Theorists recruit new followers: by pointing to something that the potential follower has no explanation for, and then asserting that this explanation has been kept from them (even if it is just a Google search away in most cases).
They build an unreasonable expectation and then attack it to make a point.
You need to very careful which expectations you accept: are they just coming from your "intuition", or are they actually reasonable? Which standards of proof are normally applied?

As an example, you are assuming that the book you'd like to read is a book that has a market and that "needs to be written", yet you haven't done any even superficial market research. You're expecting that because you (who knows nothing about book publishing) think it's a good idea, it actually is. That's not a reasonable expectation.

It's also why I pointed you to two books on "why structures (don't) fall down", so you can get some context that informs your expectation on what engineers can know about collapses; and also the NTSB investigation of the pedestrian bridge, so you can adjust your expectation about what depth of data you need to conduct a successful investigation.

If you take a step back with that in mind, and re-examine reality:
Science journalists should find this fact in itself interesting enough to explore.
If that was true, science journalists would have explored it. But they didn't explore it. Hence, they didn't find it interesting. If you now think about why this might not be interesting to science journalists, you are a reasonable person. If you are now looking for an explanation why the science journalists don't do what you expected them to do, you're walking down the rabbit hole; a hole that opened up from your own unfounded expectations.

There are two ways to deal with reality. Choose carefully.
 
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Thomas B

Active Member
The public believes the engineers can explain it
Yes, what that means is that (the public believes that) an ordinary science journalist (after making a few phone calls) should be able to identify (a) several "leading" engineers who understand the collapses and (b) a "definitive statement" about the collapses (usually by one of those leading engineers) in the literature. I can't actually do that with any certainty these days. I'm all ears if someone else can.
 

Jeffrey Orling

Senior Member
Yes, what that means is that (the public believes that) an ordinary science journalist (after making a few phone calls) should be able to identify (a) several "leading" engineers who understand the collapses and (b) a "definitive statement" about the collapses (usually by one of those leading engineers) in the literature. I can't actually do that with any certainty these days. I'm all ears if someone else can.
I would assert that there are no necessarily much in the way of published material in technical journals discussing ROOSD. I believe I recall one technical paper about column free floor systems engineering issues. ROOSD was a term coined by Tom at the 911FF... a few people arrived at this concept without doing formal engineering papers. It really is trivial.

I don't know of any core led collapse initiation papers. There was some discussion at the 911FF.

There was more curiosity about 7wtc. Cantor, the design of the frame believed the trusses played a huge role. FEMA thought the trusses were in the mix. Many dismissed trusses as the drivers and the focused was on col 79.

Can't prove a thing without real time data!
 

Thomas B

Active Member
Can't prove a thing without real time data!
But isn't this where modelling is important? All three buildings had well-known structures. It must have been possible to narrow down the failure scenarios that were compatible with observation (such as it was).

PS: What is the story of how they figured out WTC7? I mean who was thinking about it? What did they do to test their ideas? And how did they finally settle on column 79? It must be a fascinating story that all engineers would want to read about.
 
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Mick West

Administrator
Staff member
PS: What is the story of how they figured out WTC7? I mean who was thinking about it? What did they do test their ideas? And how did they finally settle on column 79? It must be a fascinating story that all engineers would want to read about.
Haven't you read the NIST report? They settled on column 79 because it's was obviously the first to go. It's not that fascinating. I personally think the human story of the investigation would be interesting, but I don't think the audience is really that huge. I would be happy to be proven wrong though.
 

Jeffrey Orling

Senior Member
You raise two issues and I may not be the best person to respond.

7wtc. The first actual movement was the collapse of the East Penthouse. If that roof structure collapsed... what supported IT has to have failed. Was it JUST below the EPH or was it a column or several columns which extended from the foundation to the EPH... failing at any height from foundation to roof? I think they decided where based on visual evidence of smoke coming through the facade. Where there's smoke there's fire... so someone determine that fires were at that level and led to the failure which led to the collapse of the EPH.
However... how the failure of a single column progressed to and entire building collapse was not explained by NIST.

++++

Turning to the twin towers?
Same sort of analysis informed the creation of an hypothesis. The effect of fire is settled knowledge. So what would fire do to the trusses? Would would it do to the slabs? What would it do to the columns? To to the bracing steel beams inside the core? Where was the fire? Smoke is seen exiting the facade... But does that mean that this was where the fire was? Where would the smoke from fires in the core exit?
Trusses were light steel and would "respond" quicker and more dramatically to fire than a steel bracing beam of column.

NOTE however the NIST theory is built on the impact of heat on massive steel beams and girders in the NE corner framing into col 79. Why would not light steel sections act in a similar manner inside the core of twin towers under the influence of elevated heat from the fires?

Where was the fuel for the fires?

The uniformity of the collapse of the top block seems to discredit NIST's heated truss theory as it implies all the trusses would have to be acting the same at the same time.... uniform high heat throughout the floor. A single truss analysis cannot be extrapolated to the entire array of floor trusses on a single floor. And there is no visual evidence that the entire perimeter was pulled in at the same instant. NIST heated a model of a single 35' truss. The truss failed and NIST went on to build their truss failure theory.
 

Thomas B

Active Member
They settled on column 79 because it's was obviously the first to go. It's not that fascinating.
That may be right. But then surely there's an interesting story of bureaucratic inefficiency to explain why it took seven years to state the obvious?
 

deirdre

Senior Member.
But then surely there's an interesting story of bureaucratic inefficiency to explain why it took seven years to state the obvious?
actually the story of how the NIST investigation went down is interesting. you should read the NIST report.
 

Mendel

Senior Member.
But isn't this where modelling is important? All three buildings had well-known structures. It must have been possible to narrow down the failure scenarios that were compatible with observation (such as it was).
You validate a model by comparing its output to observed reality. If you have several models that are compatible with "collapses in a big dust cloud", how do you propose they can narrow it down?
Please understand that unless you can tie it down to the real world with observed data, a model is no more than a guess.

That may be right. But then surely there's an interesting story of bureaucratic inefficiency to explain why it took seven years to state the obvious?
Where do you get "surely"? What did they actually do in those 7 years? Why did it actually take so long?
You are simply making an unfavorable, unwarranted and impolite assumption by assuming inefficiency is at play, with no factual basis.
 

deirdre

Senior Member.
Perhaps one (the main??) reason Thomas has this request is that the reality is that there has not been a consensus about the collapses AND the details of those collapses.
so how is his book going to be any different then the NIST report? Granted you could add 3 or 4 theories about the details from other sources (weidlinger etc) which would be interesting, but still the author is picking and choosing which to write about and which to leave out.

If Thomas doesnt think the team of NIST (with the most data to study), meets his authority criteria, then who does really? Basically he said such a book could keep people from falling down the rabbit hole... an admirable endeavor but i personally there are already documentaries out there that do that.

Ive stated before that i saw a doc before joining MB that i felt completely explained how the building was built, and why it was built that way, and how and why it fell. For the majority of the public i think such information is out there already.. as Mendel said, a very small percentage of people care about the column number.
 

Mick West

Administrator
Staff member
Well maybe among others like 77, 80, 81, or E3 or E4 or TT1, or TT2... They all failed... but which went first? 79 got the nod because of the girder framed into it on the north,
It's in the report. C79 is by far the most obvious candidate, although it's possible from exterior observation along that C80 might have been first, or that other columns somehow failed undetectable.

But at the point where we first see collapse, C79 had failed. So the task then was to find out why.


https://www.metabunk.org/f/files/NCSTAR_1-9_WTC7_unlocked.pdf
Metabunk 2020-10-14 13-09-02.jpg
 

Thomas B

Active Member
It was obvious that C79 failed. What was not obvious was why C79 failed.
It seems that you read my original post somewhat uncharitably. (That happens here quite a bit, in my experience.)
I asked, "How did they settle on C79?" And suggested that this was part of a fascinating story.
You then said, "They settled on column 79 because it was obviously the first to go. It's not that fascinating."
So I granted that for the sake of argument and suggested that, if that's true, there would then be another interesting story about why something so obvious took so long to figure out.
Now you say that it was not obvious why it failed.
But surely scientists wouldn't "settle" on a failure mechanism without understanding why it failed. So, reading me with even a modicum of charity, that must have been part of my original "how did they settle," right?

In any case, we now so seem to agree that there was an interesting story there all along.

Some of the questions that this story answers may be easy or obvious. Some suggest more interesting puzzles. The point of this sort of book is to bring them all together for laypeople. When people see the video of WTC7 coming down for the first time, very few people (and probably none) have the knowledge to say, "Oh, obviously column 79 failed!" Some have the expertise to say, "A critical column probably failed under the penthouse." And it would be interesting in itself (at least for laypeople, but also many engineers and engineering students) to learn how quickly that hypothesis was introduced, whether it was indeed uncontroversial, and how they arrived, finally, at column 79 and why it failed.
 

Thomas B

Active Member
You are simply making an unfavorable, unwarranted and impolite assumption by assuming inefficiency is at play, with no factual basis.
See my response to Mick. I was obviously drawing out an implication of his point for the sake of argument. I was saying that even if that were true (and it may or may not be) it seems to imply a criticism of the government's process -- and therefore an interesting story. (It turns out he was just reading me uncharitably, so maybe NIST is off the hook.)

But I would remind you that it's our civic duty not to worry too much about being polite to our political institutions. (As the opening minutes of that Feynman movie "dramatically" suggest.)
 

Mendel

Senior Member.
But I would remind you that it's our civic duty not to worry too much about being polite to our political institutions. (As the opening minutes of that Feynman movie "dramatically" suggest.)
That is not a "reminder". I don't think Feynman advocated being impolite. I don't think he was.
Your stance is familiar, but Feynman is not its most prominent source; I consider it uncivilized. (I'm also drawing a line here, because going further would derail the thread.)

You can be critical and polite. You saw that I advocate asking questions? (And seeking answers to those, perhaps, before you ask?)

A political process is often a process of finding a consensus, or building a consensus of where there is none, at least among a majority. Science works the same way: you collect data, you verify it, and you use that to convince others and answer their questions; all this has to be done before a scientific idea becomes established science. A scientific fact doesn't just need to be discovered, it needs to be defended.

The NIST report needed to be based on such a broad consensus; it needed to come with as many answers as possible to establish this power to convince, and to that end, it needed the input and co-operation of many people. It's job wasn't to find out what had happened; that was known, at least in general. Its job was to back it up as firmly as they could manage. Since this involves a political process, that takes more time than having a single person expound their theory. This time taken is "not a bug, but a feature". It's the whole point. It ensures that the result is actually worth something. It's where its "authority" comes from.

You can always attack without consideration. You can accuse a fast result for not being thorough, or a thorough result for being slow, and often you can do both because if you are in a position of doing something, you often need to strike a balance between the two goals.

May I remind you to walk a mile in the other guy's shoes before passing judgment?
 

Jeffrey Orling

Senior Member
The column 79 was the culprit for the collapse of the EPH. How the column 79 failure turned into the global collapse was not visually obvious. So they came up with theories to explain how col 79 failed and then how multiple floors framed into col 79 then failed which led to col 79 buckling and without explanation the global collapse ensued is the claim.

Perhaps the disturbing take away from this is that a single column failure result in a total building collapse. WTC 7 has 81 columns in all. Again no explanation of the "runaway" process which they punt on and call global collapse. Admittedly the precise path of the runaway is hard to know. But surely they could make an attempt to detail a likely possibility.
 

Jeffrey Orling

Senior Member
@ThomasB
I think a good read might be a comprehensive look at 9/11 from the perspective of how people reacted to it. For sure there was an overwhelming consensus to seek retribution and go after the "terrorists". In no time this morphed into the war with Iraq. It defied credulity that the USA could not use its resources to get UBL, out him on trial and reveal how the plot came to be, was carried out and succeeded. It also seems that such a process would reveal failings of the "authorities" to act/protect the people against threats and raise the issues of preventing crimes which have not happened. This is only possible if a conspiracy can be proven. But we did see a rise in extra legal actions such as drone assassinations following 9/11,
The pivot to the Iraq invasion was shameless as Iraq played no role in 9/11.
Further terrorist attacks persisted post 9/11 around the world and continue to this day.
Did the plotters expect the towers to fall? If so how did they know this result? That is if they did some sort of engineering... why was it so difficult for western engineers to model the result... after the fact with the two examples from 9/11?
In the months and years post 9/11 I was one of millions who wanted to understand what happened both how the rag tag terrorists pulled off the attack... and why / how massive buildings could collapse so quickly like a stack of jenga blocks? The video of the collapses lacked tell tale unequivocal signs/evidence of typical "explosive demolition" used for buildings.
We learned fairly quickly that fire / heat was the culprit. And with the collapse of 7wtc not hit by a jet it seemed to confirm it was fire which was the root cause of the collapses.
Let's ignore the conspiracy theories for the time being.
So.... engineers set about to figure out how fire could lead to the structure failing and the buildings collapsing. It seemed apparent (to me) that the fire had to set off a chain of events...one thing leading to another sort of like one domino falling ultimately causing the entire row to collapse. It also occurred to me that a set of dominoes with each on increasing a small amount in size (mass) the entire row would still fail. So you could have the first domino 1.5" tall and the last one 1.5 yards (for example and the smallest one could ultimate;y lead to to the collapse of the tallest domino even 100 (or whatever) size larger. This is a sort of the straw that broke the camel's back example.
So... the explanation would be a "chain reaction" caused by fire.
Solving the problem... became... where was the fire? and what structural elements of the building were impacted by the fire. In a wood structure the fire CONSUMES the structure.... it combusts. This is not what happened in these steel and concrete buildings.
This became a problem of what and where was the fire acting on the structure to initiate a chain reaction of failures.
The chain reaction... the links in the chain that are failing became important to understand. NIST attempted this when they presented how col 79 might have failed. But they did not carry the chain reaction... runaway collapse forward. They simple used the term "global collapse" ensued. This was to me unsatisfying.
The chain reactions are a bit of a black box... we can see what goes in and what comes out... but we can see inside the black box.
Of course Every-Man will feel enlightened (pun intended). Experts dodges the black box... even mentioning it... and surely no writer will attempt to detail the invisible. But sure... any expert COULD provide a view to what is a possibility of what is happening inside the black box... or several possibilities. Is it controversial that the same outcome can arise from different paths / causes?
Who wants to tackle black box dynamics?
 

Jeffrey Orling

Senior Member
This my friends is the problem:

"In science, computing, and engineering, a black box is a device, system or object which can be viewed in terms of its inputs and outputs (or transfer characteristics), without any knowledge of its internal workings. Its implementation is "opaque" (black). Almost anything might be referred to as a black box: a transistor, an engine, an algorithm, the human brain, an institution or government.

To analyse something modeled as an open system, with a typical "black box approach", only the behavior of the stimulus/response will be accounted for, to infer the (unknown) box. The usual representation of this black box system is a data flow diagram centered in the box.

The opposite of a black box is a system where the inner components or logic are available for inspection, which is most commonly referred to as a white box (sometimes also known as a "clear box" or a "glass box"[1])."
 

Thomas B

Active Member
I don't think Feynman advocated being impolite. I don't think he was.
I was thinking of a particular scene in the movie where Feynman's sense of humor was taken as simply insulting. A fellow physicist says he's been "in Washington for a few years" and Feynman asks him, "How's your integrity?" That ends the conversation with the government scientist.

You can be critical and polite.
Indeed, "bureaucratic inefficiency" is an exceedingly polite way of broaching a subject that might include everything from simple incompetence to downright corruption. When I say we must not worry too much about being polite when critiquing our political institutions it's because such failings are not uncommon there.

The NIST report needed to be based on such a broad consensus; it needed to come with as many answers as possible to establish this power to convince, and to that end, it needed the input and co-operation of many people. It's job wasn't to find out what had happened; that was known, at least in general. Its job was to back it up as firmly as they could manage.
This is eerily resonant with that Feynman movie. He was shocked to discover that the Rogers Commission wasn't set up to figure out what happened but to manage a consensus. Fortunately for everyone, Feynman will be Feynman. (Again, I know it's a work of fiction. I'm using it as a shorthand for what I'm pretty sure is the consensus view about the Challenger investigation. Feynman's dogged scientific curiosity and cantankerousness had a positive effect.)

...going further would derail the thread.
I don't know. I think the Rogers Commission is an good analogy for what I'm talking about. It produced a report but also a legend. The report wasn't the only source of knowledge about the investigation, nor even of what happened to the shuttle. There was intense interest in the accident and the effort to both discover and cover up its causes.

So we know a great deal about how that sort of science gets done. Using what we know about the Rogers Commission as a model, we know almost nothing about the NIST investigation. We know mainly the "official" story. The investigation appears to have followed, as Rogers puts it in the movie, "an orderly and proper procedure," and one that was not disturbed by a Feynmanesque character.

This lack of drama might have made it seem less interesting to journalists. But the scientific journey of "discovering and defending" the facts (as you put it) was still there and still worth knowing about. My suspicion is that science journalists have been, precisely, too polite about the inquiry, and that was for what I think are obvious reasons that become less and less relevant as time goes on and we get some emotional distance from the event itself. It's time to allow ourselves to be curious about this.
 

Jeffrey Orling

Senior Member
NIST gave the impression that they "solved" the problem of how the buildings collapsed. What they did is offer supported theories of how they collapsed. Or as has been noticed... there are many roads to Rome... they took one of them.
 

Keith Beachy

Senior Member
... we know almost nothing about the NIST investigation. ...
Actually, we know everything about the NIST investigation - they published it. All we have to do is read it. It is not secret, it is not hidden. We can see why they investigated, they published why.

After reading NIST - which is easy to find...
https://www.nist.gov/topics/disaster-failure-studies/world-trade-center-disaster-study

https://www.nist.gov/topics/disaste...ade-center-disaster-study/about-investigation

https://www.nist.gov/topics/disaste...enter-disaster-study/publications-and-reports

https://www.nist.gov/el/final-reports-nist-world-trade-center-disaster-investigation

It appears the WTC towers collapsed due to fire after fire proofing was dislodge by impacts of aircraft with kinetic energy equal to 1600 and 2000 pounds of TNT (that is 7 and 11 times more energy than Robertson designed the shell to stop) - the collapse progression was due to floors being overloaded which connections failed between the floors, shell and core. What did NIST get wrong? The things that NIST got wrong, do they change the outcome?

There are other studies about the WTC, one found that thicker shell steel would stop the impacts. I can look up that study if needed.

I can't find any support for CD past the less than 0.1 percent or less of those Gage has fooled to sign a silly petition asking for a new study to support CD, with no evidence for CD.

What do you believe? Is it hard to figure out the floors fail when overloaded?

It is sad the losses of 911 left the FDNY unable to mount a fire fighting effort to save WTC 7, with conspiracy theorists adding WTC 7 to their smoking gun fantasy of CD. When studying the WTC complex disaster due to terrorists, I studied other fires from Philadelphia to Madrid and others, and see that fire fighting helps save building, water helps save buildings, even if they are totaled and removed like One Meridian Plaza in downtown Philly. (something I knew 50 years ago, before studying the WTC)

Did someone comment on the time it took to finish the reports? How long did it take us to do our thesis for our masters, or those who had to earn a PhD and a dissertation (which usually have narrow scope, unlike the WTC disaster) - takes a year or 18 months if you are lucky. Now take a complete report NIST did, the time and effort is like many theses and dissertations. When doing research, some projects take the work of a dozen studies in sequence and parallel to finish the goal when you are in grad school, efforts that take years, efforts of many students.
 

Thomas B

Active Member
Actually, we know everything about the NIST investigation - they published it. All we have to do is read it. It is not secret, it is not hidden. We can see why they investigated, they published why.
We know everything that a government agency wants us to know about an investigation it was commissioned to do. In the case of the Rogers Commission, by contrast, we also know what journalists and other researchers learned through their own inquiries.

There are a lot of openly available materials about the process of the NIST investigation. The process itself was indeed pretty transparent, with public presentations along the way. The advisory board meetings were also open to the public (I remember listening in on some of them) and there are minutes.

What we are missing is any independent, journalistic interest in and curiosity about these materials. We are assuming that both NIST and the original architects/engineers of the buildings did a good and thorough job.

But people on this forum seem undecided (or in disagreement) about whether the WTC buildings behaved "normally," i.e., as one would expect any tall building to behave, or were uniquely (but understandably) vulnerable to total collapse under the circumstances of 9/11. An issue like this came up in one of those advisory board meetings:

Q: Why would these fires have burned for as long as they did? If beams sagged, buckled, and pulled they had to be exposed to the fire for more than 20 minutes.

A: The critical issue is the combination of temperatures to which the beams are exposed and the duration of that exposure ... The sensitivity to heat was compounded by the very large spans ...

Q: It sounds like you are questioning the use of spray-on fireproofing for a 2hour rating on a wide flange beam as effective fireproofing in the absence of sprinkler systems.

A: What we are beginning to find is that ratings of individual components may not be a sufficient indicator of the thermal response of the larger structure.

Q: I am not questioning what you are doing, I am questioning the way that American architects and structural engineers design buildings with spray-on fireproofing. I think you are basically coming out with a conclusion that maybe it does not work.

A: We will not make a recommendation at this point. Your input is very meaningful to us,and when all of the analysis is finished we will be in a position to make a statement about design practices.

What I'm missing is the media coverage of the follow-up on these points. If investigators were questioning how buildings are designed in America, then either those questions were answered, or design practices changed, or a bit of both. But surely it's all interesting stuff -- for both the engineers who design buildings and the public that uses them.

It's fine to refer me back to the totality of materials NIST published on the collapses and their own investigations. But that doesn't help the public. Someone needs to represent the public's curiosity about this, and their (fully warranted) concerns about the safety of tall buildings.

One question I keep asking (mostly myself, and have never found an answer to) is what the Chicago FD would do if a 767 crashed into the Aon Center. Would they expect it to collapse within an hour or two because of its design similarities with the WTC towers? I think that question itself would be a nice hook for the whole book I'm imagining. (Or choose some closer structural analogue if it exists.)
 
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Jeffrey Orling

Senior Member
@Thomas B Since the performance of building materials.... particularly steel which is the main material used for the structure of tall buildings... is known... engineers developed strategies to "protect" the building for "rated" hours... I believe the idea was that this period would allow occupants to get out of the building safely. These "hr ratings" was also applied to things like then enclosure of egress paths.

I don't know that there were engineering studies about what would happen to steel structures for fires that lasted longer... or what would happen if the fire protection (hr rating) strategies failed.

Essentially the "what if" failure scenarios were done after the fact in the "forensic" analysis post collapse as the public demanded explanations how "fire" could completely collapse a massive steel framed tower.. of which there are thousands around the world.

We are told that the sprinklers failed and that in some areas the sprayed on fire protection was dislodged but the plane impact. Both of these failures were ascribed to the plane strike. In the case of 7wtc the sprinkler failure was ascribed to the damaged water mains which occurred when 1wtc collapsed. Presumably the spray on insulation was not dislodged.

So in all three buildings we are told that the strategies to "deal with" fire failed. It should be noted that there was ample time for 7wtc to be evacuated and no lives were lost there. The twin towers revealed poor design of the exit paths, particularly for such tall buildings. Of course there were people killed by the plane impacts. But the vast majority died in the collapse because people could not get out of the building fast enough.

The question of do engineers study how their designs would perform in an extensive unfought fire is a interesting one. I would guess they do not. Structural designs include significant safety factors. So if a floor is designed to support 100#/SF live (super imposed load)... it does not "fail" when this load is exceeded... What would happen is the floor would deflect/sag. A floor (or beam) which is designed economically might be lighter, and springy... but it would not collapse. Obviously material cost drives design in the sense that less materials, lighter materials means less strong but it also less expensive. Developers seeking to maximize profit will want to to minimize cost and see economical design solutions... and so the engineers are pressured to produce lighter designs with less steel and faster fabrication / erection procedures.

When one looks at the twin towers' structural design it is apparent that the engineers optimized the design for cost... and in so doing used innovative systems such as light weight long span floor trusses allowing column free floor space. Light weight concrete which did not have stone aggregate but light weight ash for example. The outside the core floor systems were fabricated off site and hoisted in place as pre assembled components and bolted together like an "erector set".

Of course the engineers understood that the load a typical floor slab could support before failing... and that when a floor failed... or a section of a floor failed from being over loaded.... it would set off a run away unstoppable collapse to ground. A dropped wrecking ball would punch through one floor after another. A dropping floor would destroy every floor below it. It did not matter of the floor area came down in one plate... all at once... (pancakes)... or in bits and pieces over time... Local overload is unstoppable from a collapse perspective. ROOSD was not unknowable. It was understood by every engineer and architect who used a load /span design table.

What does fire do to "rolled sections"... the steel use for bracing and columns? Again this is known science/engineering. And real world studies have been done (https://global.ctbuh.org/resources/...formance-based-fire-engineering-in-the-uk.pdf).

Engineers do not run "what ifs" to model how their designs will collapse. And for the most part do not design mechanisms to arrest a run away collapse. All complex systems... of which building structure is an example are subject to "runaway collapse".

So... how likely is the collapse of multiple floors inside the twin towers? How likely would entire floor plate collapse be? What would be the scenarios for such events?

Perhaps a more concerning unanswered question by NIST is... when (what conditions) does a single column failure lead to the collapse of an entire building? It appears that in the case of 7wtc... the building would have not totally collapsed were it not for the transfer structures required to build a high rise over a Con Ed substation.

There were a lot of important lessons to be learned from the collapse of these designs. Were those lessons learned?
 
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Jeffrey Orling

Senior Member
I would argue that an important take away about the three collapses can be summed up with one word:

RUNAWAY

NIST seemed to focused their effort to identify a possibly cause(s) for the initiation of the collapses:
twin towers - sagging floor trusses
7wtc - failure of column 79 flr 12/13.

The rest of the collapse is attributed to "global collapse"

But not mentioned is that global collapse is a vague term for runaway non stoppable collapse. In all three cases there was a PROCESS associated with the global collapse. And there are questions to be asked.... such as:

What is a global collapse?
Why didn't these designs arrest runaway collapses?
What structural designs (features) would mitigate against runaway collapse?
What design features of the WTC buildings favored runaway collapse?
Was this known at the time that these designs were produced?
Is designing to prevent runaway collapse a consideration of the engineers?
Are designs which would not go runaway more expensive to design and erect?
 

deirdre

Senior Member.
It will need to be a multi-volume encyclopaedia - the scope and theme changes every time the topic drifts to another question or yet another response loses the plot.
yea and now we need for the writing team:
a trusted authoritative expert engineer on skyscrapers who is also aware of all the 911 collapse papers out there.
a popular author to make it readable and interesting
an investigative journalist to dig up the alleged "dirt" and ask the right questions.
 

benthamitemetric

Senior Member
We know everything that a government agency wants us to know about an investigation it was commissioned to do. In the case of the Rogers Commission, by contrast, we also know what journalists and other researchers learned through their own inquiries.

There are a lot of openly available materials about the process of the NIST investigation. The process itself was indeed pretty transparent, with public presentations along the way. The advisory board meetings were also open to the public (I remember listening in on some of them) and there are minutes.

What we are missing is any independent, journalistic interest in and curiosity about these materials. We are assuming that both NIST and the original architects/engineers of the buildings did a good and thorough job.

But people on this forum seem undecided (or in disagreement) about whether the WTC buildings behaved "normally," i.e., as one would expect any tall building to behave, or were uniquely (but understandably) vulnerable to total collapse under the circumstances of 9/11. An issue like this came up in one of those advisory board meetings:



What I'm missing is the media coverage of the follow-up on these points. If investigators were questioning how buildings are designed in America, then either those questions were answered, or design practices changed, or a bit of both. But surely it's all interesting stuff -- for both the engineers who design buildings and the public that uses them.

It's fine to refer me back to the totality of materials NIST published on the collapses and their own investigations. But that doesn't help the public. Someone needs to represent the public's curiosity about this, and their (fully warranted) concerns about the safety of tall buildings.

One question I keep asking (mostly myself, and have never found an answer to) is what the Chicago FD would do if a 767 crashed into the Aon Center. Would they expect it to collapse within an hour or two because of its design similarities with the WTC towers? I think that question itself would be a nice hook for the whole book I'm imagining. (Or choose some closer structural analogue if it exists.)
Is there a point to this thread any more other than for @Thomas B to complain about things about which he is ignorant? He's made it clear that he only has a foggy idea, at best, about what the breadth and depth of the actual content of the NIST reports, and now he's plowing ahead complaining about a lack of journalists covering the changes to changes to building codes that were brought about by the NIST's recommendations in the NIST reports. What happens when we demonstrate to him that those building code changes were reported on by journalists to the same extent that building code changes--which are of very little interest to the general public--are covered. Where then does this thread go? Surely to some new vague complaint @Thomas B has with some aspect of the NIST report, or the coverage thereof, about which he is simply ignorant. Let's see.

Here's some coverage of some of the many building code changes and changes to engineers' thinking brought about by NIST's recommendations:

Building Code Changes​

NIST was not prescriptive in its recommendations. Instead, NIST encouraged competitive solutions to the issues it raised and supported public policymakers to adopt revised standards and codes By 2009, the push for new construction standards won out, bringing sweeping changes to the International Building Code and the International Fire Code, which serve as the basis for building and fire regulations across the United States. The International Code Council (ICC) approve changes every three years when the codes are updated.


Some of the new safety requirements for buildings included additional stairways and more space between stairways; stronger walls in stairwells and elevator shafts; reinforced elevators for emergency use; stricter standards for construction materials; better fire-proofing; backup water sources for the sprinkler system; glow-in-the-dark exit signs; and radio amplifiers for emergency communications. ...

From: https://www.thoughtco.com/what-we-learned-after-911-178422

... One of the mysteries that SOM had to address was why the towers collapsed in the first place. Holt, whose office was just blocks away from the World Trade Center, remembers looking out his window and thinking that the buildings’ sprinklers would eventually kick in. “I never imagined they would fall,” he says. “I had made it north to Chinatown when somebody stepped out of a bodega and said, ‘They’re both gone.’ “

As we now know, the impact of the planes alone was not enough to cause the towers’ collapse. The combination of the impacts and the fires in their aftermath were what proved fatal. Not only had the planes knocked out parts of the buildings’ structural frames, they also severed and disabled the sprinkler systems’ supply pipes. As the fires continued, the remaining structure weakened to the point where the failure of one critical structural element begat the failure of the next–what architects call “progressive collapse.”

Now, Holt says, top-tier buildings like ours have been redesigned to prevent that kind of collapse. These skyscrapers have steel connections capable of redirecting the path of the upper floors’ load downward through other structural members if one should fail. And sprinkler supply lines have been located within an impact-resistant core–a major difference from the Twin Towers. Both innovations are now part of New York City building codes. In addition, the newest SOM buildings have two interconnected standpipes, so that if one should fail, the other can compensate. ...

From: https://www.fastcompany.com/1664969/how-911-changed-the-way-skyscrapers-are-designed

... The nation’s building and fire codes historically have been responsive to tragedy. Whether it was the 1906 San Francisco earthquake, the 1911 Triangle Shirtwaist fire in New York City, or more recent natural disasters such as Hurricane Katrina, construction codes have been reevaluated to address the consequences of natural disasters. The Code Council’s activity heightened when the National Institute of Standards and Technology, a federal agency, released its Report on the Collapse of the World Trade Center, which contained 30 broad recommendations for the model codes, standards industry, design community and emergency responders.

“ICC evaluated the recommendations related to model codes, and initiated code change proposals designed to mitigate the effects of a terror event in case preventive measures such as governmental intelligence activities or building security somehow failed,” Lewis said. “The code change proposals were not all successful, although many were incorporated. Some that were not have since prompted activity in other areas such as structural design to address the concerns. Some of the code change proposals resulted in higher construction costs, but others were so simple they had little or no cost impact, but great potential benefits.”

Changes to the International Codes as a result of 9/11 include:

  • Elevators are required in high-rise buildings more than 120 feet tall so firefighters can get to, and fight fires, without walking up from the ground floor with heavy equipment;
  • An additional stairway for high-rises that are more than 420 feet tall;
  • In lieu of the additional stairway, an option to provide enhanced elevators that can be used by the building occupants for emergency evacuation without waiting for assistance from emergency personnel;
  • A higher standard for fire resistance in high-rise buildings more than 420 feet tall;
  • More robust fire proofing for buildings more than 75 feet tall, which will be less likely to be dislodged by impacts or explosions;
  • Shafts enclosing elevators and exit stairways that have impact resistant walls;
  • Self-luminous exit pathway markings in all exit stairways that provide a lighted pathway when both the primary and secondary lighting fails; and
  • Radio coverage systems within the building to allow emergency personnel to better communicate within the building and with emergency staff outside the building supporting the response.

From: https://www.fireengineering.com/2011/08/29/206170/9-11-code-changes/

When buildings collapse killing hundreds – or thousands – of people, it's a tragedy. It's also an important engineering problem. The 1995 collapse of the Alfred P. Murrah Federal Building in Oklahoma City and the World Trade Center towers in 2001 spawned many vows to never let anything like those events happen again. For structural engineers like me, that meant figuring out what happened, and doing extensive research on how to improve buildings' ability to withstand a terrorist attack.
The Conversation


The attack on the Murrah building taught us that a building could experience what is called "progressive collapse," even if only a few columns are damaged. The building was nine stories tall, made of reinforced concrete. The explosion in a cargo truck in front of the building on April 19, 1995, weakened key parts of the building but did not level the whole structure.

Only a few columns failed because of the explosion, but as they collapsed, the undamaged columns were left trying to hold up the building on their own. Not all of them were able to handle the additional load; about half of the building collapsed. Though a large portion of the building remained standing, 268 people died in the areas directly affected by the bomb, and in those nearby areas that could no longer support themselves. (A month after the attack, the rest of the building was intentionally demolished; the site is now a memorial to the victims.)

A similar phenomenon was behind the collapse of the World Trade Center towers on Sept. 11, 2001, killing nearly 3,000 people. When exposed to the high temperatures created by burning airplane fuel, steel columns in both towers lost strength, putting too much load on other structural supports.
Until those attacks, most buildings had been built with defenses against total collapse, but progressive collapse was poorly understood, and rarely seen. Since 2001, we now understand progressive collapse is a key threat. And we've identified two major ways to reduce its likelihood of happening and its severity if it does: improving structural design to better resist explosions and strengthening construction materials themselves. ...

From: https://www.usnews.com/news/articles/2016-09-09/how-building-design-changed-after-9-11

...NFPA has undergone an evolution of its own in the decade following one of the most calamitous moments in America’s history. On that day, nearly 3,000 people died in attacks on the World Trade Center and the Pentagon, and in an airliner that crashed near Shanksville, Pennsylvania. A wealth of new provisions have entered NFPA codes and standards as a direct result of 9/11, changes that have affected building safety, first responder safety, and much more. A new NFPA committee has taken high-rise safety to new heights by strengthening NFPA’s life safety and building codes. Firefighter uniforms and breathing apparatuses have undergone significant upgrades, thanks to provisions safeguarding users against an array of chemical, radiological, biological, explosive, and nuclear threats. New discussions are taking place about the role of elevators during emergencies in high-rise buildings. Federal agencies and departments formed after 9/11 have reshaped the concept of emergency preparedness using NFPA 1600, Disaster/Emergency Management and Business Continuity Programs, to help launch an array of efforts designed to enhance public safety and preparedness throughout the U.S.

"9/11 will always be considered one of the worst days in American history, and it will also certainly be one of the most important days in the history of NFPA because of our long, forceful advocacy of preparedness, further safeguards to the built environment, and support for emergency responders that followed the attacks," says NFPA President James Shannon. "NFPA has been a very important part of the country’s effort to do everything we can to prepare, in case anything like 9/11 ever happens again."

On this tenth anniversary of 9/11, three efforts stand out as examples of the crucial role NFPA has played in helping create a broad culture of safety: communications and interoperability for emergency responders, high-rise building safety, and emergency preparedness. Each is a direct outgrowth of 9/11, and each is central to that event’s legacy of safety — a legacy that promises to shape fire and life safety initiatives for years to come. ...

From: https://www.nfpa.org/News-and-Resea...-October-2011/Features/A-Decade-of-Difference

,,,
Not surprisingly, new buildings, those under construction and those on the drawing board have a number of features that older buildings did not.

In New York City, for example, stairwell enclosures in high-rises must be wider and made of harder materials, and elevator shafts must be stronger as well.

To prevent the pancaking that happened at the World Trade Center as one floor fell onto another, the city requires high rises to be built to prevent “progressive collapse,” but it doesn’t spell out how to do that.

Even in places where codes have not been updated, some high-rises are taking steps to strengthen their buildings, said Jon Schmidt, an associate structural engineer and director of anti-terrorism services for the Kansas City, Mo.-based Burns & McDonnell, an engineering, architectural and consulting firm.

Materials and measures once reserved for military and government buildings gradually are becoming more mainstream, including concrete-encased stairwells to protect evacuating tenants and laminated glass that is less likely to shatter into fragments during a blast, Schmidt said.

More attention is being paid to fireproofing material that better sticks to steel — an issue that got a lot of attention because the jets that hit the twin towers apparently knocked the coating off the girders to the point they softened and broke.
...

From: https://www.insurancejournal.com/magazines/mag-features/2011/09/05/213616.htm

I could go on all day posting links to such articles. The coverage of building code changes that were inspired by the NIST reports was wide spread, robust and diverse. Those who worked in the relevant fields related to the design and maintenance of high rise buildings doubtlessly had ample sources of information from which to draw upon to understand the changes. And there was and is nothing stopping a curious member of the general public from understanding them as well.

It's clear that there is no single book in existence that satisfies @Thomas B's ever evolving requirements. But it's also increasingly clear that a lack of such a book is not @Thomas B's actual issue. The actual issue is that he has not done rudimentary research about aspects of the collapse about which he nonetheless chooses to hold an opinion. Maybe someone could write a book that would cure him of his general ignorance about the 911 investigations and that peculiar habit of his regarding them, but I doubt that going around in circles with him for pages and pages on this forum is going to accomplish either.
 
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deirdre

Senior Member.
Is there a point to this thread any more other than for @Thomas B to complain about things about which he is ignorant?
careful, i got an impolite warning for pointing that out earlier.

but yea he also is trying to negate everything proven on Metabunk because you guys are all amateurs and you all suck or something.
 

Mendel

Senior Member.
But people on this forum seem undecided (or in disagreement) about whether the WTC buildings behaved "normally," i.e., as one would expect any tall building to behave, or were uniquely (but understandably) vulnerable to total collapse under the circumstances of 9/11
I don't see anyone arguing that the WTC buildings are in any way special, or that most other skyscrapers would certainly survive such a catastrophic crash. Crashing an airliner into any building except a nuclear reactor containment (which is supposedly designed for it) will have unanticipated serious results.

There a bridges in Italy (and othe rstructures as well) that collapsed which were found to have substandard concrete in them. I don't think anyone has suggested similar issues with the WTC.

It's fine to refer me back to the totality of materials NIST published on the collapses and their own investigations. But that doesn't help the public. Someone needs to represent the public's curiosity about this, and their (fully warranted) concerns about the safety of tall buildings.
It's bad form to argue in the name of "the public" if you don't have surveys or similar data to back it up. Be honest and state that this is your own impression and your own desire, but that you're not willing to back it up with an investment (or are you?).

The twin towers revealed poor design of the exit paths, particularly for such tall buildings. Of course there were people killed by the plane impacts. But the vast majority died in the collapse because people could not get out of the building fast enough.
I recall the wikipedia article saying that everyone beneath the impact survived; but that only 4 people of the floors above the aircraft impacts did. The people above the impact couldn't get out at all because there weren't enough any escape routes not blocked by fire; those below could get out fast enough. Is this incorrect?
 

Mendel

Senior Member.
It's clear that there is no single book in existence that satisfies @Thomas B's ever evolving requirements. But it's also increasingly clear that a lack of such a book is not @Thomas B's actual issue. The actual issue is that he has not done rudimentary research about aspects of the collapse about which he nonetheless chooses to hold an opinion.
A big issue is that we're looking at claims that aren't backed up by evidence: " If investigators were questioning how buildings are designed in America, then either those questions were answered, or design practices changed, or a bit of both" is not a claim of evidence, it is a profession of ignorance. Metabunk wasn't set up to cure ignorance, it is set up to debunk claims backed by evidence.
We have this restriction because it's very easy for anyone to pull questions and claims out of thin air, as we are presently witnessing.

Nonetheless, thank you very much for your overview of the impact that the WTC collapse has had on building codes!
 

econ41

Senior Member
careful, i got an impolite warning for pointing that out earlier.

but yea he also is trying to negate everything proven on Metabunk because you guys are all amateurs and you all suck or something.
In the OP Thomas B identified his primary focus as:
I've been waiting for something definitive and detailed in this vein to be published. Something that requires ordinary intelligence and a grasp of highschool physics to follow.
... and he later imposed criteria - variously worded - about "published" and "the collective views of the engineering profession". Those OP questions have been answered many times.

His input to discussion has since been dominated by what can be described as a "rolling Gish Gallop" of evasive topic changing diversions. And several members have caused or gone along with the drifting "off topic".

The discussion is circling around the topic - classic "divergent thinking" - which raising more and more off focus questions when the OP topic has already been answered.
 

Thomas B

Active Member
Is there a point to this thread any more other than for @Thomas B to complain about things about which he is ignorant?
I can only say that I entirely accept the moderation of this forum so far. This thread (which I started) restarted by moving a contribution of mine from another thread here. I'm fine with that. It continues because people engage with the things I say. (And people also seem to be engaging with each other regardless of what I say or don't say.) When that stops, I'll certainly not post a series of "complaints" into an empty room. But I find all of this (or at least some of it) informative and useful and no trouble at all. I don't know what this "What's the point?" concern is actually about.
 
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Thomas B

Active Member
Here's some coverage of some of the many building code changes and changes to engineers' thinking brought about by NIST's recommendations:
I'm not sure exactly what you typed into Google or some other search engine, but I got more or less the same results pretty quickly. Like I say, a book by a qualified science writer to sort the wheat from the chaff in all of this would just be nice. It doesn't exist. And early on in this thread, that's basically what you and everyone tried to explain to me -- it doesn't exist and there's no need for it because it's all there in the NIST report.
 

Thomas B

Active Member
What is a global collapse?
Why didn't these designs arrest runaway collapses?
What structural designs (features) would mitigate against runaway collapse?
What design features of the WTC buildings favored runaway collapse?
Was this known at the time that these designs were produced?
Is designing to prevent runaway collapse a consideration of the engineers?
Are designs which would not go runaway more expensive to design and erect?
I've mentioned him before, but I just noticed that his book is available in an open access version online version. Uwe Starossek may be (if you have reason to think otherwise let me know) a leading expert in this area, and has written "the book" for experts/students. It's the popularization of his ideas, with a focus on 9/11/WTC that I'm imagining. And which doesn't exist.
 
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