Buckled Structural Steel in Building Fires

[Thomas B]

I'm the one who claims it won't work, remember?

The argument is not about whether any one configuration will work. The question is whether any structure of this sort of complexity (i.e., simplicity when compared to the actual WTC towers) can fail top-down under its own weight after standing up under plausibly "adverse" conditions.

If you don't like the toothpicks, just suggest another connection. If you don't like paper, suggest other materials. If you think it's too small, say how big it needs to be.

I think it should be possible. As I understand you, you don't think it's possible, using such an easy-to-understand design concept, to make a model that can meet those two conditions. And you don't think it's important. I disagree with you about that last point too.

I think you're right that, for me, to give up on this sort of modelling is basically the same thing as becoming a truther. Or at least granting them the point about the collapses.

 

[Mendel]

I think it should be possible. As I understand you, you don't think it's possible, using such an easy-to-understand design concept, to make a model that can meet those two conditions.

Does this meet your conditions? And if not, why not?
https://www.metabunk.org/threads/to...-the-collapse-of-the-wtc-towers-on-9-11.7396/

 

[Mauro]

Making engineering scale models is much more tricky than usually assumed, because dimensions do not all scale the same.

As an example, how do I make a scale model of a pillar? If a scale, say, every dimension of the pillar to one tenth of the original, the weight of the pillar will be 1/1000 of the original (10 cubed), but the section of the pillar will be only 1/100 of the original (10 squared). So every square meter of the pillar section will only support 1/10th of the original weight, and if you want to study the ability of the pillar to sustain its own weight you will need to use a material which is only 1/10th as resistant (or 1/10th as dense), which is usually not an easy thing to do (*).

Now add in some more variables you can be interested in, say potential energy, which scales with the 4th power of the linear dimension (three powers for the mass, one more for the height) and the modelling quickly becomes an inextricable mess, which at best is a serious work for specialized engineers and where often the different constraints become impossible to satisfy at the same time (**). So, no wonder a scale model of WTC can have problems in replicating the collapse. At the very least, building it would require a serious engineering effort, if it's possible at all.



(*) By the way, this also explain why the usually hyped claim 'ants can lift 100 times their boidy weight' is, actually, a triviality.

(**) Off rtopic, but one of my favourite examples of a scale model spectacularly failing is the 1:200 model of the Vajont basin and dam, in northern Italy, which was made in 1961 to study the possible effects of an avalanche falling from Mount Toc into the Vajont artificial lake. It was a pretty big model:



Di VENET01 - Opera propria, CC BY-SA 4.0, https://commons.wikimedia.org/w/index.php?curid=55348340
https://it.wikipedia.org/wiki/Disas...el_modello_idraulico_del_serbatoio_del_Vajont

and it was made by competent (even if wishful thinking) engineers. After one year of experiments they concluded that there were no risks, provided the lake level would be lowered to a 'safe' height. The lake level had just been lowered to the prescribed height when, on October 9, 1963 Mount Toc gave way and a big avalanche fell into the lake. The resulting wave from the 'safe', according to the model, lake level overtopped the dam by (it's been estimated) something like 250 meters, resulting in a mega-tsunami which claimed the life of (officially, many corpses, buried under meters of mud, have never been found) 1917 people. https://en.wikipedia.org/wiki/Vajont_Dam

 

[Thomas B]

Does this meet your conditions? And if not, why not?
https://www.metabunk.org/threads/to...-the-collapse-of-the-wtc-towers-on-9-11.7396/

It's not a piece of folded paper?

Seriously, we've been through this. Mick's model cannot stand up to an impact that would break through its vertical structure (sever its columns). Nobody thinks (not even Mick) that it models the strength of the towers under ordinary conditions. It only models a proposed collapse mechanism.

 

[Mendel]

It's not a piece of folded paper?

Seriously, we've been through this. Mick's model cannot stand up to an impact that would break through its vertical structure (sever its columns). Nobody thinks (not even Mick) that it models the strength of the towers under ordinary conditions. It only models a proposed collapse mechanism.

Which brings me back to my earlier points.

Mick defines "standing up under plausibly "adverse" conditions." as "throw a wrench at it", while you now require a three-step procedure of

• break vertical structure while model remains standing
• damage model further somehow
• watch it collapse under its own weight

The first step was not in evidence in your own attempt. You look like you're shifting the goal posts.

And your first step is a truther requirement.

 

[econ41]

Which brings me back to my earlier points.

The debate is circling now as it has the previous 4-5-6 times it has been raised.

You look like you're shifting the goal posts.

It is cyclic. Repeatedly making the same dubious steps of reasoning. I won't try to rigorously define the sequence - I'm not sure it has been consistently followed anyway.

But the elements include:
(1) a presumption that a/the model will somehow help some persons understand WTC Twin Towers collapses. Counterarguments that the "target" is vanishingly small have not been addressed.
(2) a presumption that a single model can represent the actual WTC Twins collapses as occurred on 9/11. >> Whilst ignoring the reality that comprehensive modeling of the full process needs to model FOUR very different stages with different mechanism details.
(3) Failing to recognise that modeling a specific collapse (2 times WTC Towers on 9/11) requires a prior understanding of how those mechanisms operated. The person performing the modeling MUST already know what he is modeling. The implied but often forgotten assumption being that some third person will be the one who benefits from learning from the model.
(4) Getting lost between "modeling" building block elements or parts of a collapse process OR modeling the full complexity.

And add on the two or more overriding prohibitions of cognitive behavior - limitation of the "learning person's" cognitive ability to visualise the overall scheme.

And your first step is a truther requirement.

The whole process is doomed to go round in circles. Which is, de facto, a "truther" goal whether intended to not.

And at the risk of once again stating the obvious. Define what the objective is and stop changing it every few posts.

Is it "Have fun making models" OR a legitimate attempt to build an explanatory model for some third parties?

If the latter I still doubt that there is a legitimate third party for whom a simple explanation would not be more effective. There are only four key factors that are needed to understand WTC Twin Towers collapses. A person who cannot understand how those factors combine will not have the cognitive skill to interpret any practical form of model. Because the shortcomings of the model will present a bigger cognitive challenge than working from clearly understood four key factors.

 

[FatPhil]

bold mine:

Making engineering scale models is much more tricky than usually assumed, because dimensions do not all scale the same.

As an example, how do I make a scale model of a pillar? If a scale, say, every dimension of the pillar to one tenth of the original, the weight of the pillar will be 1/1000 of the original (10 cubed), but the section of the pillar will be only 1/100 of the original (10 squared). So every square meter of the pillar section will only support 1/10th of the original weight, and if you want to study the ability of the pillar to sustain its own weight you will need to use a material which is only 1/10th as resistant (or 1/10th as dense), which is usually not an easy thing to do (*).

Oh noes! You've made the disparity worse!

(But this reinforces your point - scaling ruins modelling.)

 

[FatPhil]

The debate is circling now as it has the previous 4-5-6 times it has been raised.

It is cyclic. Repeatedly making the same dubious steps of reasoning. I won't try to rigorously define the sequence - I'm not sure it has been consistently followed anyway.

Any sequence that at any point contains the statement "Please let's not have the old discussion about "scaling" etc." is doomed to not achieve anything.

 

[Mendel]

Any sequence that at any point contains the statement "Please let's not have the old discussion about "scaling" etc." is doomed to not achieve anything.

"Please don't explain to me (again) why it's physically impossible to meet my demand."

 

[FatPhil]

"Please don't explain to me (again) why it's physically impossible to meet my demand."

Ah, doubling down, eh? Just like the towers.

 

[Thomas B]

Any sequence that at any point contains the statement "Please let's not have the old discussion about "scaling" etc." is doomed to not achieve anything.

"Please don't explain to me (again) why it's physically impossible to meet my demand."

My next sentence was:

Just describe the smallest, cheapest thing you can imagine that is both strong in the relevant ways and vulnerable to same kind of collapse.

I'm saying, let's not keep explaining the problem of scaling, which I understand. Just tell me how big the piece of paper has to be; or what other material it must be made of.

Don't tell me that the only structure that can possibly collapse like the WTC in Earth's gravitational field is one that is exactly as big (and exactly as complicated) as the WTC and made of exactly the same materials.

I want the simplest, cheapest model of the lateral strength and the vertical vulnerability that made the WTC collapses possible.

 

[FatPhil]

I'm saying, let's not keep explaining the problem of scaling, which I understand.

That is a claim made without evidence, and with many many posts of counter-evidence. You've just added to that latter corpus with your last post.

 

[Mauro]

Oh noes! You've made the disparity worse!

Damn, you're pretty right I knew engineering modelling is hard (I studied it a little, but it was 40 years ago!) and I trusted myself only in making the most basic example possible... and I succeeded in making a mistake nonetheless. As Phil correctly points out, the density should be 10 times higher, not 1/10th.

(But this reinforces your point - scaling ruins modelling.)

That's the important thing. Scaling makes modelling at best very difficult and needing specialized engineering knowledge, and it can even be impossible (unless one scales 1:1 or nearby, ofc!)

 

[Thomas B]

That is a claim made without evidence, and with many many posts of counter-evidence. You've just added to that latter corpus with your last post.

Is there a scale at which a paper model could meet my challenge?

 

[Mendel]

Don't tell me that the only structure that can possibly collapse like the WTC in Earth's gravitational field is one that is exactly as big (and exactly as complicated) as the WTC and made of exactly the same materials.

No, Mick's structure does that just fine.

But you're going to want it to collapse exactly as the WTC did, as evidenced by your above shifting of goal posts; and that can't be done because it's physically impossible.

 

[Mendel]

Is there a scale at which a paper model could meet my challenge?

No.

 

[Thomas B]

No.

Could you do it in steel?

 

[Mauro]

I want the simplest, cheapest model of the lateral strength and the vertical vulnerability that made the WTC collapses possible.

I'm sorry but I cannot help you, as I (and others) tried to explain, it's not an easy problem at all and it's quite possible that, indeed, the only physically realizable model of WTC collapse...

... is one that is exactly as big (and exactly as complicated) as the WTC and made of exactly the same materials.

But, in case you want to try to build a model again (surely I won't), I can give you a piece of advice: familiarize yourself with scale modelling and the problems involved. I looked for some reference source which discusses the problem (I would have liked to get a refresh on the topic myself), but I could find nothing suitable and freely available (I guess scale modeling is rather demodé in this era of computer simulations). If you want, you could try this (sold on Amazon):




From the look of it, it seems a promising book (but I cannot guarantee).

 

[Mendel]

Could you do it in steel?

Not as a scale model, no.

The main difficulty is that your challenge is not precisely defined, so it's impossible to determine if any given model meets it.

 

[Thomas B]

Not as a scale model, no.

The main difficulty is that your challenge is not precisely defined, so it's impossible to determine if any given model meets it.

Would you be willing to help me define the challenge in terms that you would accept? We could start another thread.

 

[Mendel]

Would you be willing to help me define the challenge in terms that you would accept? We could start another thread.

not really. you're just shifting the conversation to what challenge terms you'd accept.

Just describe what a successful challenge would be: what would a video of it look like? What numbers would you want to know? What conditions on these numbers must be met?

 

[econ41]

Any sequence that at any point contains the statement "Please let's not have the old discussion about "scaling" etc." is doomed to not achieve anything.

Don't I know it. Both points - the reality of scaling problems and the overt wish to ignore the issue.

BUT I did play along with the request and omitted it from the partial list of errors. Mea culpa.

 

[Thomas B]

not really. you're just shifting the conversation to what challenge terms you'd accept.

Just describe what a successful challenge would be: what would a video of it look like? What numbers would you want to know? What conditions on these numbers must be met?

I think I've been pretty clear about this. So you'd need to be willing to get into some weeds for me to understand what your issues are. If you can't be bothered, neither am I.

 

[econ41]

Would you be willing to help me define the challenge in terms that you would accept? We could start another thread.

The challenge is easily defined - You got close with this comment - if we remove the foggy conditionals:

I want the simplest, cheapest model of the lateral strength and the vertical vulnerability that made the WTC collapses possible.

And, as has been said several times, and you choose to ignore:

...modeling a specific collapse (2 times WTC Towers on 9/11) requires a prior understanding of how those mechanisms operated. The person performing the modeling MUST already know what he is modeling.

Do you agree that you cannot model something if you don't understand what you are trying to model?

Do you understand how the WTC Towers collapsed?

THEN you can consider if modeling is plausible and practical.

And best abandon the alleged aim to "help others understand" because there are far more effective methods than modeling.

 

[Thomas B]

Do you understand how the WTC Towers collapsed?

I do not.

 

[econ41]

I do not.

Thank you, So that is step #1

Do you agree that you cannot model something if you don't understand what you are trying to model?

So learn how the towers collapsed FIRST then you know what you need to model.

 

[Mendel]

I think I've been pretty clear about this.

No, you haven't. That's my point.

So you'd need to be willing to get into some weeds for me to understand what your issues are. If you can't be bothered, neither am I.

If you can't be bothered to do this:

Just describe what a successful challenge would be: what would a video of it look like? What numbers would you want to know? What conditions on these numbers must be met?

then your challenge isn't worth bothering with.

It can't be met.

 

[econ41]

No, Mick's structure does that just fine.

Take care - the moving goalposts problem.

Mick's structure only models the fourth and final stage of the four stages of collapse. The "established progression" or "ROOSD" stage. @Thomas B is attempting to model the whole collapse - therefore all four stages.

And Mick and those of us advising him all understood the mechanism he was modeling. @Thomas B does not have a clear understanding of the four stages he wants to model.

 

[Jeffrey Orling]

This is a fool's errand because you cannot scale forces / strengths of materials. How do you scale gravity?

 

[Thomas B]

So that is step #1

No, it is step zero, square one.

So learn how the towers collapsed FIRST then you know what you need to model.

I am asking people who claim to know how the towers collapsed to model them in ways I might understand.

 

[FatPhil]

This is a fool's errand because you cannot scale forces / strengths of materials. How do you scale gravity?

Do it on the Moon! Or on Jupiter, depending which way you wanted it to go.

In a centrifuge?

 

[Thomas B]

If you can't be bothered to do this

I am saying that I have done this in great detail. It's possible you honestly missed it. But if you agreed to start a separate thread, with the aim of working out what sort of model would be fair to demand of someone who claimed to know how the WTC collapsed, then I would be willing to spend, literally, weeks and months clarifying the terms of that problem again. If not, there's no hard feelings.

 

[econ41]

No, it is step zero, square one.

I am asking people who claim to know how the towers collapsed to model them in ways I might understand.

Once again you evade, shift the goalposts and circle.

Neither I nor we are the ones trying to build a model to explain the full collapse mechanism.

You can legitimately ask "us" to explain the collapses. You CANNOT legitimately demand that the explanation be by a method that is impossible or impractical.

Why are you limiting your method of gaining understanding to physical models?

 

[Thomas B]

Why are you limiting your method of gaining understanding to physical models?

Because I want to understand the physics of the collapses.

 

[Jeffrey Orling]

Because I want to understand the physics of the collapses.

What aspect don't you understand? The collapse involved "failures" of many "sub systems" which made up the entire structure "scheme".
For example... do you accept that any floor has an imposed load under which it will fail? Do you accept the notion that the sub systems... such as the slab support at columns or the belt girder had load limitations? So the static buildings slabs were self supporting on the seats... including live load and a "safety factor" - additional load. When and if there are failures above... that material "descends" (dynamically) on the the intact floor below it. When the descending load exceeds the capacity of the floor system it falls on... that floor system will fail and this becomes a sort of chain reaction. The columns were not what failed initially... it was the connections to the columns. And that "freed" a dynamic load to descend on an intact floor. A typical floor had an upper limit of the load (force) it could support. When that was exceeded that floor fails and a chain reaction ensues. The plane impact created a situation where mass which was "locked" into the structure was freed... essentially leading to overloading of the floors in succession.
A second mechanism was related to the loss of bracing of columns. When bracing is removed the load capacity of a column is reduced... and can become lower that the service loads.
Two types of failures:
slab
columns

 

[econ41]

Why are you limiting your method of gaining understanding to physical models?

Because I want to understand the physics of the collapses.

Please stop it.
Your objective is "Because I want to understand the physics of the collapses but only when explained by a physical model."

Stop shifting the goalposts every time you are given a legitimate answer.

Explaining the collapses is relatively easy.

It is not practical and probably implausible to attempt it by modeling.

As I and other members have explained many times.

Let's see if you are serious about understanding:"

The Twin Towers collapses involved four stages with differences of mechanism at each stage <<accept that as the foundation unless you can prove it wrong.

Stage 1 "initiation" > a cascading failure of columns allowed the "Top Block" to start moving bodily downwards. Do you understand** that key point "start moving bodily downwards"?

Stage 2 "transition" as the Top Block started to drop the ends of the broken columns in the Top Block missed he columns in the lower tower. Do you understand** that key point?

Stage 3a "early progression" as progression commenced the interactions between column ends and floor joists/beams caused shearing of the joists/beams resulting in the breaking up of the Top Block and upper levels of the lower tower. Do you understand** that key point "shearing of floors off columns caused break up"?

Stage 3b "established progression" AKA "ROOSD". The progression continued with debris from disconnected floors and dismantled upper levels falling in the floor areas - office and core spaces. Do you understand** that key point "falling debris caused floors to be sheared of?i
to

** And, please, no evasions. Four key stages of collapse. Four key factors - one at each stage. Do you understand the actual simple four points I made? NOT do you understand the details of physics. If you DO NOT understand "start moving bodily downwards" and similar we can define it better BEFORE we need to prove how it happened.
IF you cannot join in reasoned discusion - we ca

 

[Thomas B]

The collapse involved "failures" of many "sub systems" which made up the entire structure "scheme".

The three decades preceding the collapses involved the "performance" of those same sub systems. I want to reconcile these two facts.

 

[Mendel]

Because I want to understand the physics of the collapses.

You can't replace a course in civil engineering with looking at a model.
Another impossibility.

What will looking at a model provide you with that looking at the actual collapse doesn't?

 

[Mendel]

The three decades preceding the collapses involved the "performance" of those same sub systems. I want to reconcile these two facts.

Reconcile
• aircraft impact
• multiple big fires
not happening in the 3 decades prior.

Not acknowledging that = truther tactic.

How the building went from "working fine" to "broken" is described in the NIST report.

 

[Mendel]

I am saying that I have done this in great detail. It's possible you honestly missed it.

Then please quote it. Simple enough, right?