Mendel
Senior Member.
that's nice to hear, I get told sometimes that we're not good at it
I think most of us love answering questions, and that's why we're easy to troll.
but as long as we're having fun doing it, I think it's all good.
Buckled Structural Steel in Building Fires
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I think most of us love answering questions, and that's why we're easy to troll.
but as long as we're having fun doing it, I think it's all good.
psikeyhackr
Member
Oh really? Then why are there sources saying that there were 425,000 cubic yards and they existed before 9/11 and the NCSTAR1 report does not even specify a total though they agree with those sources on the total amount of steel.
For some reason NIST says that WTC7 had 28,000 tons of steel. A somewhat curious relationship with each of the Twin Towers being twice as tall and having about 4 times as much steel. So did the lower half of the towers have 3 times as much steel as the upper half. The Eiffel Tower has to cope with the same gravity but does not have to support double it's own weight in concrete.
Oystein
Senior Member
What's wrong with 425,000 cubic yards?
And if 425,000 cubic yards are wrong, what does it matter to you? We still know the dimensions of everything if we even need to know.
How about there are probably sources that are mistaken and there are sources that are correct?
Huh?
Why should NCSTAR1 report specify a total - what purpose could that possibly serve?
You see, I happen to know exactly how much money is my wallet - how many coins and bills of each denomination, but I could not specify the total weight of that money. So what?
Did you expect NIST to read your particular mind and provide numbers that you wish, for entirely unclear reasons, to be in the report?
And if NIST failed to pre-emptivly read your, psykeyhackr's mind to give you a number you would demand years after the report, does that mean the report is broken, invalid, worthless?
No.
Curious indeed, what you write there. You are not making any sense.
Don't know, and why is that relevant? What purpose would be served if you knew the answer to this?
No, the Eiffel Tower has to cope with a lot less "gravity".
And anyway - so what?!? Totally different structure with totally different purposes facing different challenges.
Hint for you: If you expose enough of the Eiffel Tower - any part of it - to enough of a fire, it WILL collapse. Under gravity.
That's what gravity does to tall things that aren't stable any longer. It's really simple. You don't need to know the exact weight or how its distributed to understand the general principle.
Gamolon
Active Member
425,000 cubic yards of concrete in the ENTIRE World Trade Center complex, not the twin towers alone.
https://www.911memorial.org/learn/r...er was completed,York City to Washington, D.C.
Concrete floors outside the core were approximately .3333' (4") x 208' x 208' which equals about 14,420 cubic feet of concrete. The core was 87' x 135'. So subtract that out of the total 4" floor slab amount calculated previously. So 87' x 135' x .3333' equals about 3,915 cubic feet. 14,420 - 3,915 equals 10,050 cubic feet of concrete for the 4" slabs outside the core.
Using 5" thick slabs for the core gives us .41666' (5") x 87 x 135' which equals about 4,894 cubic feet of concrete in the core for one floor.
10,050 cubic feet for the 4" thick slabs equals 372.222 cubic yards. Multiply by 110 floor equals 40,944 cubic yards.
4,894 cubic feet used for the 5" thick slabs in the core equals 181.25 cubic feet. Multiplied by 110 floors equals 19,938 cubic yards.
40,944 cubic yards for the 4" slabs plus 19,938 cubic yards for the 5" slabs gives us 60,882 cubic yards for the floor slabs in one tower.
That's 121,764 cubic yards of concrete in both towers combined.
Either you misunderstood what the 425,000 cubic yards of concrete was used for or you think there's 303,236 cubic yards of concrete hidden within both towers somewhere.
Mendel
Senior Member.
What source says this?
Where does NIST say this?
Why is it curious? What are the footprints and the enclosed volumes?
That sounds about right.
If you consider a triangle with one side as its "floor", then the bottom half has 3 times the area of the top half.
For a pyramid, the ratio is even worse.
I'm not sure what your post is meaning to evoke, but my reaction is "shrug" and "so what?".
Gamolon
Active Member
I don't consider it a waste of time as anyone coming to this forum (or any other) may see what was posted by psikeyhackr and consider it as questions and that they are posting in good faith.
In my opinion, it's never a waste of time to educate people regarding the posting habits and misinformation of others, even if it is trolling.
psikeyhackr
Member
Oh no, not the infamous psikeyhackr spreading misinformation.
How can there be any misinformation about the distribution of steel down the Twin Towers if there is no information about the distribution of steel down the Towers?
The NCSTAR1 report by the NIST could not fit it into 10,000 pages.
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Mendel
Senior Member.
The NIST report references the structural drawings of wtc 1 and 2. They're online.
econ41
Senior Member
Hi psikey! Long time no chat.
You are certainly both persistent and consistent with your half-formed hypothetical questions about the distribution of steel and concrete.
The members here - other than me - are probably not as familiar with your work or your prominence in online debate some 12 - 15 - whatever years back
For the information of @Gamolon and @Mendel I confirm that you were one of the earliest persons to undertake serious physical modelling of aspects of Twin Towers collapses.
Members should find this video interesting. It raises questions but, sadly, seems to be down a false trail. Something that psikey and
I discussed at great length at least 10 years ago,
Enjoy:
So the apparent assumption psikey made back in 2007 (??) was that the collapses of the Twins somehow resulted from oscillatory resonance as a direct consequence of the aircraft impacts. A fair enough hypothesis to consider in those early days. It was 3-4 years before the correct explanations were published on-line in lay person understandable language. Remember that prior to about 2009 both the academic/professional formal debate and the informal online debate were down false trails.
The collapses were not caused by oscillatory resonance. And were not the direct consequence of aircraft impact impulse or momentum effects.
But psikey and I did enjoy - at least I enjoyed - explaining all the analogous concepts. Including the acoustics of organ pipes - both jopp[en and stopped. And the radio wave propagation characteristics of 1/4 wave ground plane antennae. The distribution of mass would affect the harmonic aspects of the horizontal vibration.
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psikeyhackr
Member
I know! I have seen them.
I don't recall them showing the horizontal beams in the core. It has been a while. Maybe I will look again.
I clearly remember communicating with Lon Waters PhD telling me that he could not find data on the horizontal beams.
Mendel
Senior Member.
If oscillation did not cause the collapse, then what's the use of including it in the analysis?
econ41
Senior Member
As I said all those years back and repeated in my previous post:
(a) I agreed with back whenever - 2009 or 2010 and
(b) "we" fully explored the analogies if fixed and vertical cantilevers to 1/4 wave ground plane antennae.
AND all these years later the topic of weight distribution is still of no demonstrated relevance to the analysis of the Twin Towers collapses. It is a dead end. There are multiple alternative approaches to explaining the collapses.
And I still assert that your physical model was a credible example of modeling. Arguably ahead of its time. A pity that the apparent assumption was wrong.
Note: "apparent assumption".
Which:
(a) I agreed with back whenever - 2009 or 2010 and
(b) "we" fully explored the analogies if fixed and vertical cantilevers to 1/4 wave ground plane antennae.
AND all these years later the topic of weight distribution is still of no demonstrated relevance to the analysis of the Twin Towers collapses. It is a dead end. There are multiple alternative approaches to explaining the collapses.
And I still assert that your physical model was a credible example of modeling. Arguably ahead of its time. A pity that the apparent assumption was wrong.
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econ41
Senior Member
EXACTLY my point. Actually one of my two points. ( 1 Wrong assumption and 2 Goes nowhere.)
I like the model a lot too. I like the way it demonstrates how strong the buildings were (or, if you will, how the buildings stood strong) in the face of the aircraft impact. What has always disappointed me about the official story is that it doesn't start with a model that is strong in this way and then shows how it can completely destroy itself under its own weight.
I think that's why the distribution of steel (strength) and concrete (dead load) in the buildings is important. It represents what the structure was doing every day for thirty years. Standing there, carrying it.
Mendel
Senior Member.
But the official story does?!
The NIST report goes to great lengths to show that the WTC towers were built exceeding the standards of the day. That is also what they're modeling.
Then NIST considers the fires and the heat, how that affected the dimensions and the strengths of certain parts, and how the loads shifted until some parts were overloaded, failed, and started the chain reaction that brought the building down.
(You denying this about the official story is what makes you look like a truther, btw.)
It's not the effect of the fire that puzzles me here, although I did once believe that buildings like the WTC should easily be capable of surviving complete burnout without major collapses. Localized failure of elements due to fire is of course possible.
So it's not the thermodynamics of the local failiure that I'm interested in; it's the mechanics of the global progressive collapse of the building. If someone could set up a model like the one @psikeyhackr has given us, have it behave somewhat like his does when impacted from the side, and yet have it collapse when a failure is introduced in the top fifth of the structure, I would have something to study and learn from.
FatPhil
Senior Member.
If Euler buckling is relevant, then oscillation is relevant. Euler buckling is an inability to constrain oscillation. It's the same differential equation with the same inputs. Of course, Euler buckling isn't oscillation, it's what happens when oscillation becomes impossible because a critical feedback parameter goes above 1 and you switch from sinusoidal to exponential behaviour, but it's almost impossible to talk about a situation where Euler buckling is relevant but oscillation isn't. Of course, I'm not privy to the decade-plus of ground you two have already covered, and what sub-sections of the territory have already been excluded, this is just my view from afar.
I do, however, see how "goes nowhere" is only one or two steps away.
Mendel
Senior Member.
So how is the distribution of weight relevant to Euler buckling "oscillations"?
Mendel
Senior Member.
So, like the Kai Kostack simulation?
FatPhil
Senior Member.
Please reword. I don't see how your question relates to what I wrote. The second order differential equation that describes the onset of Euler buckling is a differential equation that models oscillations. That's just a mathematical fact. A system that does not undergo Euler buckling will oscillate as a response to perturbations, that's just a physical fact.
Not last I checked. If you provide a link to the one you're thinking of it, I'll take a look and try to explain what's missing.
Mendel
Senior Member.
The context/claim here is that we need to know the "weight distribution" of a WTC tower in order to model its oszillations so that we can properly analyse and understand its collapse.
Buckling is relevant because that's what happened to overloaded columns as part of the collapse.
You argued for the claim when you wrote, "If Euler buckling is relevant, then oscillation is relevant." You argue that buckling is basically an unconstrained oscillation?
But I don't see how that is relevant to the context when it doesn't relate to the weight distribution, and we agree that it's a different physical phenomenon (a different equation).
What I'm getting at is that I don't understand why you brought it up in the first place. It seems to be a distraction if it's not related.
econ41
Senior Member
Provided we don't change the context. i.e. impact induced oscillations suggested as a factor in WTC Twin Towers collapses.
It isn't relevant in the context of explaining WTC collapses. It has some interesting aspects of applied physics BUT not in the context of the initiating topic of this current discussion.
Take care - that is also a side trail. Unless someone demonstrates relevance to the topic we are discussing.
errr... more drift??
EXACTLY. That is the topic.
Specifically as the probable trigger of the cascading column failure of the "initiation" stage. And that was not an oscillation process - simply inward bowing >> misalignment >> axial strength of columns reduced by eccentric loading. (Plus a couple of secondary factors of no immediate interest.)
It is a potentially interesting topic except not of demonstrated relevance. I opine that it is not relevant to the actual Twin Towers collapse mechanism.
Keith Beachy
Senior Member
Interesting take on the WTC steel. Thicker steel was used at the bottom of WTC towers, and thinner steel at the top. With the core and shell holding up all the floors, the steel at the base had to be thicker to support the upper sections of core and shell. This is covered in NIST, and other articles about the WTC towers.
Actually the official story does explain why the building destroyed itself after failures at the impact floors. Based on the simple fact floors do not hold up other floors in the WTC. The core and shell hold up each floor. When the top floors failed, the next floor was overloaded and failed. This is explained by NIST. This is a model, a model based math with respect to design of the WTC.
What model is needed to understand a floor in the WTC will fail when overloaded. Proof of this word/math model based on facts and design parameters of the WTC tower, are seen twice on 9/11. This is a simple math model.
Every time I try to build anything approximating it, it is either too weak to sustain a sharp lateral impact or too strong to collapse vertically. Basically, I can only get something that is assembled as losely as a house of cards to behave the way the WTC did. Anything built to absorb lateral loads (to sway in the wind) is way too strong to collapse under its own weight.
I'm happy to look at some specs for a physical realization of the "simple math model". What's the smallest, cheapest thing we can build that behaves like the WTC on 9/11 and also as it did on, say, January 6-8, 1996, during the nor'easter? (Please let's not have the old discussion about "scaling" etc. Just describe the smallest, cheapest thing you can imagine that is both strong in the relevant ways and vulnerable to same kind of collapse. That's the thing some of us struggle to understand.)
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Oystein
Senior Member
I would guess that mass and its distribution along the structural elements in question (that may oszillate or buckle), as well as the gravitational load on them bears on the outcome values when solving the second degree differential equation(s) that @FatPhil talks about. "Second degree differential equation" screams out "wave function", and as a guitar player, I can attest to you that both the mass of a string as well as the external force acting on it longitudinally are parameters that affect resulting frequency: A thicker (more massive) string has a lower frequency, all other things being equal, than a thinner string, and the larger the force with which you pull on the string, the higher the frequency.
So, it appears intuitive to me that "weight distribution" will be a set of parameters that doesn't cancel out in the mathematical system of equations that describe the behaviour of a steel-frame structure (its oszillation frequency; or the circumstances under which it buckles and how).
All that said, I am of course firmly in the camp "unlikely to get us anywhere".
psikeyhackr
Member
Yes, the Conservation of Momentum must be irrelevant it is only mass hitting mass.
Mendel
Senior Member.
yep, because it's being accelerated throughout, so the momentum isn't constant anyway
econ41
Senior Member
Yes - the actual topic has been extensively discussed. This thread has been derailed into another topic as raised by @psikeyhackr starting at post #25
The subsequent discussions are off-topic and follow a pattern of circular behavior which the member has pursued extensively over many years and multiple forums. To a lesser extent but more recently here on Metabunk.
The SOP is consistent - block the progress of the real topic of discussion by asserting a factoid of physics truth which has little relevance to the debate topic. Which does not contribute to moving the discussion forward.
As per this latest example at Post #68
You've actually built some models? That would make for an interesting thread.
econ41
Senior Member
Exactly. The concept is easy to understand. Put a load of 10 onto something that can support 1 and it fails. You don't need a model to explain that reality. Nor do you need to discuss whether or not NIST explained it correctly. You certainly don't need to rely on NIST to comprehend that load 10 beats strength 1. NIST is an irrelevant side track.
You face a fundamental problem. Circularity or 'chicken and egg". IF "you" are the one building the model you must already understand the mechanism you are modeling. So there is nothing "you" need to learn. The model may assist some third party who needs help. But then you run into the next problem. Can "they" understand the principle you model AND conceptually fit it into an overall explanation? The set of persons who need a model before they can understand a modeled principle THEN fit the principle into an overall context is vanishingly small. If they can manage the conceptual challenge of fitting the bits into the whole they surely won't need a model to explain the"bit".
And the same situation applies to all the dozens of "bits" needed to explain WTC collapses. Sooner or later the target person's ability to comprehend an interrelated lot of "bits" will be the limit. And very few, if any, of those who can fit all the bits together, will benefit from a model.
Hence the 'chicken and egg' circularity.
The baseline is almost certainly that many of us enjoy the challenge of modeling. It is fun. And rigorous logic has little to do with it. We will claim "trying to help people understand". Most of the real motivation will be the fun of doing it.
But I've made that observation on previous occasions.
psikeyhackr
Member
So you don't consider the possibility that the collapse should not have happened on the basis of how skyscrapers MUST BE BUILT?
That is why I used the weakest material I could think of, PAPER.
Then I tested the paper loops for statistic conditions. Under the dynamic conditions the falling portion did not have enough energy to take out all of the supports below.
Believing something that happens to be impossible is a problem. Why should anyone have a problem with accurate data. If the collapse was really possible then having accurate data won't hurt any supposed proof of the collapse.
Mendel
Senior Member.
Because your expectation is a misleading simplification that suggests a strong building collapsed.
But what instead happened was:
- A strong building was weakened by an airliner impact and extensive fires
- The weakened building collapsed.
NIST does not model the collapse itself, for the following reasons:
- collapse is understood to be inevitable by any civil engineer from that point
- collapse sequence is not really controversial
- lack of tools to model it
Please confine your wondering to how a broken building can progressively collapse, if you're not a truther. And then go look for the answer elsewhere, for we've previously tried to teach you that at great length, and obviously failed. See e.g. https://www.metabunk.org/threads/how-to-explain-the-structures-of-the-twin-towers-to-truthers.12072/ and https://www.metabunk.org/threads/wo...d-from-fire-alone-without-plane-impact.12533/ .
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A beautiful way to describe the mood of this place for me. Thanks for trying.
I started a couple of years ago, when we were talking about the Hoffman challenge, where I developed one of my own. But I was eventually blocked from that thread. I worked a little more on it and eventually came up with a kind "3D sketch" of the problem that looked like this. The idea is just to come up with paper dimensions (and weight of the paper), and measurements for the cutouts (which also specifies the tapering of the columns), as well a way of specifying the load on each floor (kind and amount batteries, or some other standard weight). The floor-column connections can also specified otherwise, if that makes a difference. Like I say, these models, no matter how I arrange things, are either too weak to seem like plausible "buildings", or too strong to collapse under their own weight if damaged in the top 20%.
Mendel
Senior Member.
Mendel
Senior Member.
"Please don't talk about the physical obstacles to me getting what I demand", which is not ...
This reveals you as pseudoscientist.
The free length of these columns determines how easily they buckle when subjected to a lateral load. You chose that relatively long.
I started a couple of years ago, when we were talking about the Hoffman challenge, where I developed one of my own. But I was eventually blocked from that thread. I worked a little more on it and eventually came up with a kind "3D sketch" of the problem that looked like this. The idea is just to come up with paper dimensions (and weight of the paper), and measurements for the cutouts (which also specifies the tapering of the columns), as well a way of specifying the load on each floor (kind and amount batteries, or some other standard weight). The floor-column connections can also specified otherwise, if that makes a difference. Like I say, these models, no matter how I arrange things, are either too weak to seem like plausible "buildings", or too strong to collapse under their own weight if damaged in the top 20%.
How many batteries weight can that floor design sustain? It should [only] be about 3-5 batteries worth, and then the top block needs to have 20 batteries in it, to match the WTC. What your model shows is that if the damage to the WTC had been confined to the top 3 floors, it probably wouldn't have collapsed.
But kudos for actually building one; I entered that thread a few weeks later, and didn't retain that information.
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The picture shows mainly a sketch of the problem, not a solution. This one cannot be made to collapse like the WTC. If you can draw a plan for how to cut out the holes, provide the smallest possible dimensions (for the sheet of paper A4, A3, A2, A1? ....), and, yes, tell me how to load each floor, I'm curious to hear. Like I say, I have tried and failed.
Mendel
Senior Member.
Yes.
I'm the one who claims it won't work, remember?
You can model the progressive floor failure, but you probably won't get the outer tube to collapse. The tube-in-tube design of the WTC towers means that their outer tube can be much weaker (comparatively) than your design; and your design with the toothpick seats provides very little lateral bracing for your tube, which is majorly stabilized by the corners.
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