Mendel
Senior Member.
I have quoted and linked NIST FAQ #18 here. What about it do you not believe?
How high could the plane have hit, and still caused a total collapse?
- Thread starter Henkka
- Start date
Mendel
Senior Member.
Why didn't they do that? What do you think?
econ41
Senior Member
@Henkka Do you really want to learn? Or do you want to preserve, hang on to, your suspicions about CD?
If you want to learn there are several paths you can take.
One path is the "direct" approach - discussing the actual collapses which occurred. I recommend starting with the easiest part which, coincidentally, is the bit we have been circling around in recent comments. The progression stage of Twin Towers collapse and why it was so fast because the falling debris missed the columns. Take that one first.
NEXT look at the "initiation stage" for Twin Towers. It is several grades more complicated but the main elements can be explained simply. AND that stage is essential to overall understanding of why there was no need for CD. (Because IF there had been CD it HAD to be at that stage - think about that and the reason should be clear.)
Another path is by discussing rebuttals of truther false claims. one of the first rebuttals I needed to do was of an early video by David Chandler. Which may interest you given your regard for David Chandler. BTW do you know Chandler's early history and why he became involved in the Truth Movement. He like many early truthers had genuine concerns about the politics which I respect and agree with. Sadly, like so many, he shifted focus onto false technical claims. AND for those of us who are familiar with the history - he made the very same mistakes that the early debunkers made.... Some ironies in that history. About 7 years where both "sides" were wrong and made the same type of error. (Ignoring the real collapse - favouring abstractions and gross modelling)
But, back to the offer I am making. Do you want to learn by direct discussion of the actual collapse physics? OR do you prefer to discuss the claims of Chandler, Szamboti, Coles et simile?
Or do you want to still keep going round in circles as long as the moderators tolerate the rambling?
- it's your call.
If you want to learn there are several paths you can take.
One path is the "direct" approach - discussing the actual collapses which occurred. I recommend starting with the easiest part which, coincidentally, is the bit we have been circling around in recent comments. The progression stage of Twin Towers collapse and why it was so fast because the falling debris missed the columns. Take that one first.
NEXT look at the "initiation stage" for Twin Towers. It is several grades more complicated but the main elements can be explained simply. AND that stage is essential to overall understanding of why there was no need for CD. (Because IF there had been CD it HAD to be at that stage - think about that and the reason should be clear.)
Another path is by discussing rebuttals of truther false claims. one of the first rebuttals I needed to do was of an early video by David Chandler. Which may interest you given your regard for David Chandler. BTW do you know Chandler's early history and why he became involved in the Truth Movement. He like many early truthers had genuine concerns about the politics which I respect and agree with. Sadly, like so many, he shifted focus onto false technical claims. AND for those of us who are familiar with the history - he made the very same mistakes that the early debunkers made.... Some ironies in that history. About 7 years where both "sides" were wrong and made the same type of error. (Ignoring the real collapse - favouring abstractions and gross modelling)
But, back to the offer I am making. Do you want to learn by direct discussion of the actual collapse physics? OR do you prefer to discuss the claims of Chandler, Szamboti, Coles et simile?
Or do you want to still keep going round in circles as long as the moderators tolerate the rambling?
- it's your call.
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Jeffrey Orling
Senior Member
If someone has followed the discussion about how the towers collapsed on various online forums over the last 10-15 years you will encounter much good material which sheds light on what happened.... including "debunking" of Bazant, Chandler, Szamboti, Gage and other "truthers".@Henkka Do you really want to learn? Or do you want to preserve, hang on to, your suspicions about CD?
If you want to learn there are several paths you can take.
One path is the "direct" approach - discussing the actual collapses which occurred. I recommend starting with the easiest part which, coincidentally, is the bit we have been circling around in recent comments. The progression stage of Twin Towers collapse and why it was so fast because the falling debris missed the columns. Take that one first.
NEXT look at the "initiation stage" for Twin Towers. It is several grades more complicated but the main elements can be explained simply. AND that stage is essential to overall understanding of why there was no need for CD. (Because IF there had been CD it HAD to be at that stage - think about that and the reason should be clear.)
Another path is by discussing rebuttals of truther false claims. one of the first rebuttals I needed to do was of an early video by David Chandler. Which may interest you given your regard for David Chandler. BTW do you know Chandler's early history and why he became involved in the Truth Movement. He like many early truthers had genuine concerns about the politics which I respect and agree with. Sadly, like so many, he shifted focus onto false technical claims. AND for those of us who are familiar with the history - he made the very same mistakes that the early debunkers made.... Some ironies in that history. About 7 years where both "sides" were wrong and made the same type of error. (Ignoring the real collapse - favouring abstractions and gross modelling)
But, back to the offer I am making. Do you want to learn by direct discussion of the actual collapse physics? OR do you prefer to discuss the claims of Chandler, Szamboti, Coles et simile?
Or do you want to still keep going round in circles as long as the moderators tolerate the rambling?
I find NIST was largely correct, but really missed the opportunity to explain how the collapse were runaway unstoppable processes. The suggest initial "causes" and then punt by saying this led to global collapse. So there initial causes are debatable (they got the heat cause as the driver) but their "global collapse" really misses the reason why there was pancaking. I think they failed to point out how the form of the collapses was in the "DNA of their structural designs". These were far from "garden variety" skyscrapers.
There is little to no need for formulae or calculations... But there is a huge need to have a basic understanding of how building structures "work". Some key concepts are:
1. excessive heat fatally weakens steel structures - The proximate cause is lengthening of over heated steel
2. one failure leads to another
3. there was no "arrest feature" in the design to stop a runaway floor collapse
4. when one floor fails and falls... it will cause the one below it to do the same
5. stresses (loads) move through a structure via horizontal structural elements: beam, girders, trusses, slabs
6. columns supported floors, and floors braced columns
7. column free plans tend to quickly involve the entire footprint when there is a failure of a slab.
8. what is design working load (slabs), what is designed in excess capacity
etc.
Unless I'm misunderstanding it, it seems to be only talking about the one floor immediately below the collapse initiation. I don't think anyone contests that if the top block somehow started moving downwards, it would at least destroy a few floors below. What truthers like Szamboti and Chandler claim is that the collapse would not have continued all the way to the ground, and we have John Gross on video saying they did not do any calculations on why that did not happen. We also have this statement from NIST, quoted by AE911:
Source: https://www.ae911truth.org/evidence/near-free-fall-acceleration
Another problem is that the answer talks about an amplified load, which afaik requires a deceleration, which was not observed. So for example I'm a pretty lightweight guy, my scale says I'm currently about 70kg. But if I do a little hop on to the scale, I briefly see numbers as high as 140kg. That's because I decelerate rapidly as I land on the scale, and there is an equal and opposite force applied on it. The top of the North Tower accelerated down smoothly at about 65% of g as long as it was visible, it did not decelerate. Chandler will claim this is proof that the top is not crushing what's below, but is instead falling as its supports are being removed by something else.
Now I know you guys will again be upset with me for using words like "crushing" instead of "shearing" and all the ROOSD stuff, but I'm sorry, the NIST/Bazant hypothesis is simply the mainstream, "official" explanation for the collapses. If you want me to consider ROOSD more seriously, I would need to see that it holds sway in actual scientific publications, not just online forums. Now you might accuse me of hypocrisy, since obviously there are no scientific papers for the controlled demolition stuff. But what I'm saying is that if Bazant got his analysis wrong, and ROOSD is correct, I would expect the scientific community to have already figured it out in the past 20 years. Then ROOSD would be the mainstream explanation, instead of something you just find on online forums.
econ41
Senior Member
@Henkka you face a fundamental decision. You need to choose between (a) Learning what actually happened, OR (b) continuing your trolling of evasions and denials.
AND
Whichever of those two paths you choose - serious learning OR dishonest trolling - you still have several sub-options.
As I have now said too many times to count PLEASE decide to understand the actual collapse mechanisms. IT is not too hard if taken step by step. THEN you can test the accuracy of any claim. NIST, Bazant, any members here OR all the false claims of the truth movement.
As I have said many times. It is YOUR call to decide what you want to learn or to admit that you do not. AND remember that this forum expects discussion to be "on the topic" so few if any of your more recent comments are "on-topic", and will probably need a properly framed claim in a separate OP. Again - the ball is in your court. But please decide to get serious and give up going round in circles of evasive trolling.
NOW - do you want to learn? Yes or No?
AND - identify which process of discussion you want to take as per my advice in post #203
AND
Whichever of those two paths you choose - serious learning OR dishonest trolling - you still have several sub-options.
As I have now said too many times to count PLEASE decide to understand the actual collapse mechanisms. IT is not too hard if taken step by step. THEN you can test the accuracy of any claim. NIST, Bazant, any members here OR all the false claims of the truth movement.
As I have said many times. It is YOUR call to decide what you want to learn or to admit that you do not. AND remember that this forum expects discussion to be "on the topic" so few if any of your more recent comments are "on-topic", and will probably need a properly framed claim in a separate OP. Again - the ball is in your court. But please decide to get serious and give up going round in circles of evasive trolling.
NOW - do you want to learn? Yes or No?
AND - identify which process of discussion you want to take as per my advice in post #203
So choose - learn the physics or discuss ONE claim by one of your trusted heroes. YOUR CALL.
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econ41
Senior Member
NIST FAQ #18 is misleading as I have cautioned in previous posts. And you are misunderstanding the situation. You need to understand "impulse" or "dynamic" loading. NIST FAQ #18 is not a good example because it takes a simplified approach to explanation and only focuses on one type of scenario. Which was NOT the actual collapse. (It is a play-safe lower bound explanation - the real event was more extreme... more complex, which we (or at least "I") can explain if you ever decide to get serious,.)
They are wrong. Do you want to know why? OP a thread and say you find their claims persuasive and I will explain why they are wrong.
You have already been advised that no calculations are necessary and why that is so.
The ongoing games between AE911 and NIST are not the topic of this discussion. And neither of those parties are members able to contribute. AE911 is making nuisance, dishonest and petty claims. NIST is playing the game and fobbing them off. They (AE911) don't deserve or merit anything better.
If you want to learn about "impulse" and "dynamic" loading OP a thread and ASK. NIST FAQ18 is a poor source for you to refer to. Remember your example of dropping an anvil on your toes? The NIST example doesn't explicitly address a "dropping anvil" type of impulse load situation. It is not overly complicated as I keep telling you. But you need to get serious and attempt to learn.
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Jeffrey Orling
Senior Member
There is a paper written the topic of which is runaway progressive floor plate collapse... published prior to 9/11.
Mendel
Senior Member.
Yes, you are misunderstanding it. The calculation is not limited to a specific floor, but applies generally.
Article: The vertical capacity of the connections supporting an intact floor below the level of collapse was adequate to carry the load of 11 additional floors if the load was applied gradually and 6 additional floors if the load was applied suddenly (as was the case).
Consider a typical floor immediately below the level of collapse initiation
neither tower could have arrested the progression of collapse once collapse initiated.
It's clear that any office floor in this building would have been overloaded the same. (I believe mechanical floors were a little stronger, but not that much?)
Jeffrey Orling
Senior Member
stronger, but heavier.
Mendel
Senior Member.
Your quote says they were "unable to provide a full explanation of the total collapse" because their software was unable to simulate it.
Why, do you think, did they not try it another way?
econ41
Senior Member
@Mendel This comment from NIST can be misleading:
NIST's conclusions are correct but the explanation is simplified. And is a sort of lower bound limit case. "applied suddenly" means the load in contact with what it will put force on but not loading it. So in @Henkka's "anvil" example - IF you hold the anvil in contact with his foot THENstop supporting it the is "applied suddenly". The anvil has no motion and the suddenly applied load is twice - 2 times - the actual weight. Probably tolerable for anvil on foot. BUT lift the anvil and drop it through any significant distance and the actual impact load will quickly become much more than twice the static weight. Easily 10 times without doing the calculations. So NIST's comment "(as was the case)" is not fully correct.
Mendel
Senior Member.
You are referring to this:
Article: Since the dynamic amplification factor for a suddenly applied load is 2
This is easy to google, and has nothing to do with decelaration:
The Tacoma Narrows Bridge failure is an example of vibratory response.Article: It is well-known that the responses of a structure are different when subjected to a static load or a sudden step load. The dynamic amplification factor (DAF), which is defined as the ratio of the amplitude of the vibratory response to the static response, is normally used to depict the dynamic effect.
Basically, the peaks of a wave are higher than its average level, and can destroy a connection where the average level would not.
Deceleration plays no part in the considerations of NIST FAQ #18.
Mendel
Senior Member.
What is the NIST/Bazant hypothesis?
NIST FAQ #18 is official, and it explains the progressive collapse of the floors.
Mendel
Senior Member.
Could you be a little more specific?
Jeffrey Orling
Senior Member
Mendel
Senior Member.
not before 9/11External Quote:
Jeffrey Orling
Senior Member
there are others... google is your friend
Mendel
Senior Member.
if I knew how to search for this, I would
FatPhil
Senior Member.
"the load of 11 additional floors if the load was applied gradually and 6 additional floors if the load was applied suddenly (as was the case)." cannot be stated unless there is an agreed deceleration. I'm not sure where it's derived or stated, but it must exist. The only difference between "gradually" and "suddenly" *is* the deceleration, it's an intrinsic part of that statement.
econ41
Senior Member
There is a lot that is potentially misleading in NIST FAQ #18. It is "near enough" correct for a lay person audience. I've restrained my pedantic engineering comments in this thread out of a desire to not further confuse @Henkka.
BUT on the issue of "suddenly applied" and the related issue of "impulse" loading there are three states. I'll explain using @Henkka's reference to an anvil:
1) If an anvil is resting on your foot it will apply a force equal to its actual weight.
2) If I hold the anvil in place on top of your foot but me taking the weight THEN I release the anvil the "suddenly applied" load with be 2 times the weight. That is the figure NIST relies on in FAQ #18. It is safe for NIST's purpose because the real case could not be less than 2 and would near certainly have been much more.
THEN
3) If I hold the anvil some distance above your foot and drop it the impact on your foot will be far more than one or even two times the actual weight. Depending on what height I drop it from. Multiplication factors of 10 or higher are readily achieved. I'm too lazy to do sample calculations.
You are correct to identify deceleration but let's not chase the details too far. I don't think relying on NIST FAQ #18 will help @Henkka given that he has been thinking of anvils in a "dropping to impact" scenario. But then I'm not confident that he would comprehend the subtle details either. Catch 22. Hence my lack of previous comments on the issue.
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FatPhil
Senior Member.
Yup. I've just read your earlier "Henkka's Anvil" response, and indeed I have oversimplified. There are 2 non-moving states (which are endpoints of a continuum) that NIST address, but the third state, the dynamic one (again, on a different continuum) is the one that actually applies to the WTCs. Thanks for spotting the difference between the statics problems and the dynamics problem that NIST overlooked. I'm tempted to say that their statement (just that specific bit) is at best misleading, and at worst useless now.
econ41
Senior Member
EXACTLY. Hence my frustration with whether or not to make the pedantic engineering comment.
It's one of several reasons why, back in 2007, the first couple of weeks of posting online, I decided to NEVER accept thrid party "authorities". Specifically NIST and Bazant at that time but quite a few more as the years have passed. You cannot hold some party as an authority AND still critique their claims. I've called a few errors by Bazant. I disagree with NIST on a few issues of style. Like this one - I can understand why they would simplify the explanation for laypersons. But it has its risks when a lay person asks a question where the NIST "shortcut" is not rigorously correct.
FatPhil
Senior Member.
EXACTLY. Hence my frustration with whether or not to make the pedantic engineering comment.
It's one of several reasons why, back in 2007, the first couple of weeks of posting online, I decided to NEVER accept thrid party "authorities". Specifically NIST and Bazant at that time but quite a few more as the years have passed. You cannot hold some party as an authority AND still critique their claims. I've called a few errors by Bazant. I disagree with NIST on a few issues of style. Like this one - I can understand why they would simplify the explanation for laypersons. But it has its risks when a lay person asks a question where the NIST "shortcut" is not rigorously correct.
One of the things I like the most about Metabunk is that it's one of the nicest places to make a mistake, be corrected, learn, and be better equipped to look at such matters in the future. And because of that, feel a net positive from the whole experience despite it starting with a mistake.
econ41
Senior Member
As an engineer seeking to explain WTC 9/11 collapses in the antagonistic context of "debunkers v truthers" I have always tried to be assured of the truth of any claims I make. An issue of "market credibility". IF you make one error it has more effect on credibility than any number of correct explanations. So I have always played conservative - an interesting challenge if you are also pushing the limits of contemporary wisdom...
So, in about 12 years and 40k posts on forums before I lost count I am aware of two errors that I made and were spotted by my opponents. (I may have got away with a few more
) I also had one very close call - posted some garbage on a forum and got to delete it about one minute before the "Edit Window" timed out..BUT, of those two admitted errors, one was in a one-on-one discussion with AE911 Truther Engineer Tony Szamboti. I made a mistake... he was guessing but guessed right. He reminded me about that mistake on "several" subsequent occasions. Red face stuff... and my own silly fault... grrrr....
And Murphy's Law - it had to be with a prominent Truther. ("If anything can go wrong - it will. And in the worst possible situation.")
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Mendel
Senior Member.
It's not useless, because regarding the load factors, we can order them by magnitude:
dynamic [C] > sudden static [B.] > constant static [A]
Because of this, any statement of the form O(B) "weight X will overload structure S in case [B.]" implies O(C) "weight X will overload structure S in case [C]". The advantage of O(B) is that it is easier to show than showing O(C) directly, because the latter requires more work.
And of course, the fact that O(B) doesn't involve deceleration makes it immune to Bazant and Szamboti.
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Mendel
Senior Member.
Article: 10. Why didn't NIST fully model the collapse initiation and propagation of the WTC towers?
The first objective of the NIST WTC investigation included determining why and how WTC 1 and WTC 2 collapsed following the initial impacts of the aircraft (see NIST NCSTAR 1). Determining the sequence of events leading up to collapse initiation was critical to fulfilling this objective. Once the collapse had begun, the propagation of the collapse was readily explained without the same complexity of modeling.
It seems contradictory to say the total collapse of the building was easily explainable, and then not explaining it.
Jeffrey Orling
Senior Member
The collapse have been explained. All three were "ultimately" runaway rapidly progressing floor collapses or pancaking. Various explanations have been given for what initiated the pancaking. ROOSD is a non mainstream used term for what happens to column free floor space that collapses. Any floor system which has its load suddenly increased byu 5 or 6 times or more cannot survive and collapses on to the one below and that one repeats the process. Columns which cannot arrest the floor collapse become too unstable without the bracing that the floor system provided... and they too collapse/topple/buckle.
Mendel
Senior Member.
Mendel
Senior Member.
How is this a contradiction?
Mendel
Senior Member.
Jeffrey Orling
Senior Member
Hennka does not understand the collapse... willfully ignorant... and refuses to accept that basic engineering can explain what happened.
The key takeaway is the notion of runaway progressive failure... one failure leads to the next / or many others.
The key takeaway is the notion of runaway progressive failure... one failure leads to the next / or many others.
econ41
Senior Member
That is true.
Try thinking through reasoned analysis. If you have the requisite skills. And listen to those who do understand and do have the skills if you don't.
Except failed CDs do nothing to explain WTC collapses. And, by the way, the WTC collapses did not "stop halfway".
Truthers have been playing that game for 15-20 years.
They were not "random".
For the wTC Twin Towers that is true no matter how much you evade reality.
Mendel
Senior Member.
You mean that NIST FAQ #18 does not reflect what actually happen, but instead posits a scenario that involves a smaller load from above, and less damage to the floor below.
You correctly note that the application of a moving mass imposes a greater load than the sudden application of a static mass: the actual load was much greater than the minimum load NIST computes. But this is already true because the number of falling floors exceeds the required minimum in any case.
NIST computes the minimum weight needed to make a typical floor fall by summing the strength of its connections. This strength is less than the resistance of the floor to crushing. But we know (and NIST says) that the applied load greatly exceeded that connection strength, so we can assume that parts of the floors were simply crushed, leaving some connectors unbroken but attached to small blocks of floor debris.
Using the minimums means we don't have to compute the energy of the falling debris, its distribution, and actual effect in detail, something that NIST tried but found could not be achieved by the engineering software at its disposal.
Sure, but I'd say reasoning about it is just step 1 of doing science. No matter how solid and convincing your reasoning seems to you, it should be checked through experiment. There's a famous quote by Richard Feynman explaining this principle:
So if you haven't checked your reasoning through experiment, you're still in the "guessing" phase. But we do have experiments that are at least somewhat applicable to the WTC collapses... Every verinage demolition is in effect a scientific experiment on what happens when the top portion of a building is dropped on the lower portion. And in these cases, we observe a jolt that is not observed in the WTC collapses. But people will always contest this saying the building being demolished is too different to the WTC towers. And since it's impossible to build an exact replica of the WTC towers, the only things you can do are 1) experiments on different buildings, 2) scale models of the WTC towers or 3) computer simulations of the WTC towers. If we forget about computer simulations for a bit, I've also never seen a scale model purporting to replicate the collapse of the towers.
econ41
Senior Member
Do give up the "spinning" we are analysing a set of three "one off" events that actually happened. NOT inventing some new theory of science.
I'm well aware of the multitude of times Feynman has been misrepresented by those pursuing false claims about WTC collapses. Do you seriously think that you are the first one to pay that trick?
And we - those of us who understand and are honest - know full well why there are jolts in Verinage and why there was not the type of Jolt referred to in those false claims by Szamboti, Chandler (and I think Coles)
Utter nonsense. I see no reason to persist in trying to help you when you are determined to never learn.
Jeffrey Orling
Senior Member
What aspect of the collapses makes no sense to you?
heat expanding lateral steel distorting columns leading to buckling
column buckling (losing strength) when bracing is removed or fails
tops dropping when axial capacity was driven below service loads
floors collapsing / shattering from being severely overloaded
FatPhil
Senior Member.
However, scientists are often permitted to start with experimentally-verified "A has a very high probability of leading to B", and "B has a very high probability of leading to C", and conclude "A has a high probability of leading to C". (You want to mix in a bit of "B leading to C shouldn't depend on whether A was the cause of B or not", of course, which can sometimes be a leap of faith.)
Forget about what "makes sense" for a moment. The question is what part of this can be verified through physical experiments, or if you can't do that, a computer simulation. Lots of people think it "makes sense" that the position of Saturn this week will affect their romantic pursuits, doesn't make it so.
So someone can think it "makes sense" that the columns missing would explain why there was no jolt, and be wrong. It should be checked through experiment. If you look at videos on the Tacoma bridge collapse, you will find that scientists did build physical scale models of the bridge and replicated its behaviour in wind. But it seems like that with the WTC towers, all you get is an endless barrage of excuses of why it can't be done, or wouldn't be worthwhile to do.
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