Kostack Studios WTC2 (South Tower) Collapse Simulation

[Oystein]

Simplifying somewhat, what I want to build is a structure that can replicate this effect with only the weight of 4 cans on top (compressed into a single disk). That means designing the "can" to be a good deal weaker than an actual pop can. (Imagine cutting slits and holes in it.) It must first carry that load easily and then, when a "sagging" *within the structure* itself pulls the walls of the can inwards, it buckles under its own weight, i.e., the weight of rougly four times that of the structure itself. That initiating event requires connections and structures inside the can to provide the "tap", pulling in from the inside, rather than pushing from the outside. And that gives us some sense of how strong those connections have to be. First, to hold the "floor" in place (which wouldn't require a very strong connection) but then, when it sags, not simply to disconnect from the inside of the outer wall.

Google AI tells me that an average can is 122 mm tall. So four of them are 488 mm tall. The real tower is 415,000 mm. That's a scaling factor of 1:850.

This means that the volume:area ratio should also be 1:850, if your aspect ratio happens to be correct.
This makes your model, if all linear dimensions are 1:850, is too light by a factor of 850. To compensate, you'd either have to make vertical supports 850 times weaker, or you'd need to add 850 times the weight - perhaps in the form of smartly placed blobs of lead or gold.
But then you face the problem that your model's fall height is too little by a factor of 850. To compensate, you could run the experiment in a centrifuge that creates an acceleration 850 times that of g. That's 30 times the gravity on the periphery of the sun, 10 times that of an average brown dwarf, but far less than on a white dwarf. Also somewhat less than what the centrifuges that enrich uranium are capable of.

Such a to-scale model would have to have built in so many extremes (super-thin wall, super-high density, a gravitational pull like nothing in our solar system), all waaaaaaaaaaaaaaaaaaaaay outside the human scale and people's hands-on experience, that I doubt any "Truther" would accept this as a fair, true model.

I think you are on an entirely hopeless wild geese chase.

 

[Mendel]

That initiating event requires connections and structures inside the can to provide the "tap", pulling in from the inside, rather than pushing from the outside.

if you don't understand that a push from the outside and a pull from the inside do the same thing, you're not mentally equipped to understand the collapse at the level you proclaim you want to understand it — which I suspect will shift as necessary to be unattainable anyway

 

[Thomas B]

a) I am pretty sure these numbers are quite off. As for the weight of the towers, always go with a figure of 300,000 tons. 90,000 of which were steel (including rebar; all numbers above ground level). That's a steel:nonsteel ratio of 90:210 = 1:2.33

b) I still don't get why that ratio is relevant.

a) It'd be great to nail those figures down with a good source. The lower the nonsteel proportion is, however, the harder it is to understand how the buildings collapsed under their own weight. If your figures are correct I'm even more puzzled.

b) I want to show how a dead load of only four times the mass of the supporting structure is enough to destroy that structure completely. (And like I say, only about one fifth of that, at least initially.) The example of someone standing on a popcan is not persuasive because the crushing weight is so disproportionate to the mass of the object being crushed.

 

[Thomas B]

I think you are on an entirely hopeless wild geese chase.

I appreciate these issues, and it's always good to put some math on it. The question (and I think I've said this before) is, if I let you use any material, what's the smallest possible structure that could fulfill something like my challenge?

Consider: (like I also keep saying,) I assume that a building half the height of the WTC but built on the same principles would have been just as vulnerable to total collapse. So begin by just imagining a smaller building. Then, when you get down to a scale where it would no longer collapse (because of the scaling issues you rightly raise) switch building materials that are orders of magnitude less stiff. (But try to keep the masses proportionate.)

At each step make sure that the structure is strong enough to survive a piercing blow to the perimeter walls.

We know that the WTC is a very big thing that demonstrates the mechanism. What's the smallest thing that could do it?

It's something like this that I'm working on. Maybe it's more for the journey than the destination.

 

[Mendel]

a) It'd be great to nail those figures down with a good source. The lower the nonsteel proportion is, however, the harder it is to understand how the buildings collapsed under their own weight. If your figures are correct I'm even more puzzled.

have a look at the Kostack simulation
watch how much of the steel is not involved in the collapse and simply left standing to fall away on its own
your obsession with the gross weights is a red herring
and that should be obvious because the progressive floor system failures have been explained to you repeatedly and recently
my only explanation that you're unable to apply this understanding is that you don't want to
and nothing we do can change that, that change has to come from within yourself
anything else is a waste of time

b) I want to show how a dead load of only four times the mass of the supporting structure is enough to destroy that structure completely. (And like I say, only about one fifth of that, at least initially.) The example of someone standing on a popcan is not persuasive because the crushing weight is so disproportionate to the mass of the object being crushed.

I reminded you at the beginning of this conversation that the physical properties involved here DO NOT SCALE. I explicitly mentioned buckling strength.

Also, the dead load that destroyed the WTC was far less than 4 times the mass of the supporting structure. Have a look at the collapse initiation in Kai Kostack's video, and estimate how much mass was needed to start the progression to a point where it became unstoppable.

You are wasting everyone's time because there are no signs that you are taking any of the explanations onboard. Your level of understanding has barely progressed from 5 years ago.
Intentionally.

P.S. Your posture of not being the person you speak for prevents you from asking honest questions. This is another impediment to understanding.

 

[Thomas B]

a push from the outside and a pull from the inside do the same thing

Yes, but in the pop-can example the energy in the "tap" is arbitrarily large compared to the object being buckled. To model the WTC mechanism it has to be possible to exert that leverage from a point inside the object being crushed.

 

[Thomas B]

You are wasting everyone's time

No, I'm replying to people. The only waste of time is you trying to get me to admit that I am

not mentally equipped to understand the collapse

which is a bit unfair since every time I come here I begin by saying that I don't understand the collapses.

It's possible that you're right and the problem here is my base stupidity. But in that case the decent thing to do is to ignore me, not to keep goading me into saying another thing you think is stupid.

 

[Mendel]

Yes, but in the pop-can example the energy in the "tap" is arbitrarily large compared to the object being buckled. To model the WTC mechanism it has to be possible to exert that leverage from a point inside the object being crushed.

No.

 

[Mendel]

which is a bit unfair since every time I come here I begin by saying that I don't understand the collapses.

yes.
it's been 5 years.
draw the conclusion.

And in no way did I say or imply "stupidity", that's a misunderstanding on your part.

 

[benthamitemetric]

As I've said elsewhere on this forum, science communicators have also had two decades to popularize this mechanism (cf., e.g., The Titanic, Tacoma Narrows, Hyatt Regency, Challenger, Concorde) so that curious people could learn how the buildings collapsed without having to interact directly with specialists, conspiracy theorists, and debunkers.

As Tucker Carlson's recent doc reminds us, the same old questions remain open in the popular imagination.

This Kostack video could be very helpful with a little recutting and narration -- first explaining how the enormous strength of the building was modeled (including the strength of the floor connections) and then how that strength was overcome by the unique circumstances of the 9/11 attacks. I hope Kostack either does this himself or lets a competent science vlogger do it.

I think it would be worth the effort even from a strictly monetary point of view.

Watching the building collapse from various angles for ten minutes is one thing. Zooming in and explaining the various points of failure (i.e., the actual structural elements and how they failed) would be quite a lot more instructive.

It seems to me that every year that goes by is a year with fewer 9-11 truthers. Among those who remain, the number of 9-11 truthers who wouldn't be 9-11 truthers if only they understood this particular aspect of the collapse must be vanishingly small (if such a person has ever even existed). So it seems that science communicators, including the authors of the original NIST report two decades ago, did their job on this point and there's no point of dwelling on this issue for the benefit of the few remaining truthers. But, even if you want to dwell on it for some reason, it doesn't make any sense to use a model that does not model anything relevant to this issue as the vehicle for dwelling on it. Maybe instead your time would be better used reading the two-decade-old NIST report and, if you find it wanting, trying your hand at explaining the issue better. (As is often the case, you seem confused about whether the explanation you seek is for you or for some unspecified truthers who understand the collapse less well than you, but, if the former is the case, reading the NIST reports may just finally give you the explanation you personally have been searching for and you need not undertake reinventing the wheel.) NIST even provides you with extensive and undeniable photo and video documentation of the bowing, which accompanies their accurate and succinct technical explanation of why the bowing occurred.

 

[econ41]

Maybe it's more for the journey than the destination.

Except the journey is not progressing.

No set destination.

 

[investigating911]

Here is a list of all known videos of the South Tower Collapse. The 7:42 to 8:11 portion in Kostack's video illustrates how the 82nd floor survivor glass from the east face of the South Tower might have resisted shattering, while an entire panel it was part of wedged itself into Church Street. 5:58 to 6:37 clearly showed how collapse of the South Tower split the Millennium Hilton in two prior to the collapse of the North Tower crushing all but the lower floors at the southern end of the hotel.

From the videos compared to this simulation by Kostack, one interesting aspect that might be of interest is to examine what exact visual differences between the actual collapse and simulation are present. Two visual differences between the actual collapse and this simulation regarding remaining standing parts of the structure at the base and damage to surrounding structures were present. Two differences immediately apparent in the simulation was entire collapse of tridents at the base and the base of the South Tower being surrounded by an unyielding West Street and Liberty Street. Pictures of the aftermath of the collapse of both towers show some of the tridents facing Liberty Street still standing and Liberty Street heavily caved in with South Tower debris lodged in Liberty Street. Incorporating and being able to simulate this might also be able to give a better idea of how exactly and how soon after collapse began that St. Nicholas Greek Orthodox Church was completely crushed and where in the debris field it might have ended up in.

For 9:02 to 9:38 showing views of the collapse from the plaza, it would have been helpful for visualization purposes to see the concert stage at the southern end of the east face of the North Tower and how it might have affected tower debris trajectories. The Sphere being modeled such that it could experience dents rather than rolling away and being dislodged whole after being struck by debris would also have helped show how much damage The Sphere and fountain area might have experienced before the collapse of the North Tower. Finally, views of collapse from the South Tower lobby would have assisted in examining what exactly was going on structurally at the base of the South Tower from a first person point of view.

 

[Mendel]

Consider: (like I also keep saying,) I assume that a building half the height of the WTC but built on the same principles would have been just as vulnerable to total collapse. So begin by just imagining a smaller building. Then, when you get down to a scale where it would no longer collapse (because of the scaling issues you rightly raise) switch building materials that are orders of magnitude less stiff. (But try to keep the masses proportionate.)

YOU CANNOT DO THAT.
Because. The. Physical. Properties. Do. Not. Scale.

Scale the whole building down by a factor of 2, which is what I assume you meant, yes?
This scales the volume (and hence the weight) of each floor plate by a factor of 8. The floor spans are also shorter, and hence don't sag as much.

But the cross-sections of the structural steel are scaled down by only a factor of 4, and the free lengths have halved, making them more resistant to buckling than they were before. Same for the bolts holding the floor: the floor got ⅛ lighter, but the bolts only ¼ weaker: 12.5% weight carried by 25% strength.

By the time you're at 1:10 scale, you need 60 floors worth of dynamic load to start the "pancaking" process. You need to abandon your attempt at proportional scaling while the tower is still 54m high, because you no longer have enough potential energy to break it.

And at that point, you lose every truther with Flat Earth—level physics understanding. I know that because I published a video of a small spinning ball with size and spin calculated to match Earth's centrifugal force exactly, demonstrating how we or the oceans wouldn't be "spun off", and the concept sailed well over the heads of the majority of commenters.

If you want to make your floors 10x as thick so that you still have propotional pulling force "from inside", congratulations, you now have eliminated sag entirely, and also no air left inside the tower. A concrete block 1/10 the size of a WTC tower would be entirely uncollapsible, like a modern pyramid built from steel and concrete.

Which is why your "pull from inside" condition demands the impossible.

From the start, your approach here on Metabunk has been to demand the impossible, and to disregard all explanations as to why it is impossible, as well as embarking on any alternate means to understand the physics involved. This is the reason why you've been stalled for 5 years.

 

[econ41]

YOU CANNOT DO THAT.
Because. The. Physical. Properties. Do. Not. Scale.

Lift an ant 20-30-n times its own height/length off the ground. Drop it. It runs away.

Lift an elephant 20-30-n times its own height/length off the ground. Drop it............

 

[Oystein]

...
b) I want to show how a dead load of only four times the mass of the supporting structure is enough to destroy that structure completely...

You merely repeat what you want to do. That doesn't answer the question WHY that ratio is relevant.

 

[Mendel]

b) I want to show how a dead load of only four times the mass of the supporting structure is enough to destroy that structure completely.

You merely repeat what you want to do. That doesn't answer the question WHY that ratio is relevant.

This is all about the assumption that this was not a progressive failure. He's been quoted the FAQ that a dynamic load of 6 floors was sufficient to destroy the support for a single floor, i.e. the floor braces, which must weigh thousand times less than the floor itself.

The "dead load" is distributed fairly equally across the floors, while the vertical steel is not: it's much less massive toward the top. So if we look at the buckling, we have the weight of 12+ floors (including structural steel inside the floors!) compressing vertical steel of, generously, a 3-story span, which I estimate weighed 2% of the load (4:1 dead vs steel, times 4:1 number of stories, times 2 for the steel in the floors, times 2 for the tapering, times a variable factor for load shed by the missing columns because it overloaded nearby columns disproportionally).

Force needed to bow a span is much less than it supports axially, see beverage can experiment.
Or cut a spaghetti so it fits between thumb and forefinger and crush it axially, can't do it without bowing it, and takes more force than applying lateral force while you do it.
The inward pulling force was a lot less than the weight of a single floor, but it didn't need to be, because bending is comparatively easy.

So the ratio is just a number born from constraints on how we should scale the model (by weight) which make a scale model impossible, while rejecting scale models that illuminate the principles involved.
"If my porridge isn't just right, I refuse to learn anything".
Why porridge? Chewbacca defense.

 

[econ41]

Thomas B has advised me, by message, that he has been blocked from this thread.

Yesterday at 8:53 PM New

Hi Econ

Apparently I've been blocked from replying at the forum. (LINES EDITED) Thanks for the sparring and see you next time.
Anyway, see you around next time maybe.

Cheers,
Thomas

I see no moderator announcement confirming his change of status.

 

[econ41]

Take care - there are a few assumptions developing in recent posts. First a presumption that dropping floors was the initiating factor. Possibly a consequence of the lack of clarity of the Kostack visualisation.

For the real event there is strong visual evidence that sagging of overheated floor joists caused the initial pull in of the perimeter columns. The effect is a result of the geometry of a catenary. Explanation will follow. Catenary sag pull-in has been the accepted wisdom for many years.

Bottom line is that catenary sagging can cause inwards pulling which can be, almost certainly is, many times the magnitude of the downwards force from the weight of the floor.

Therefore, the first of these assertions is not true for the real event.

The inward pulling force was a lot less than the weight of a single floor, but it didn't need to be, because bending is comparatively easy.

Here is the explanation of the theory. It comes from a conversation several of us had b DM on one of those multiple previous discussions when the main thread was closed by moderation. (Participants Scaramanga, Mendel, econ41. Circa October 2023)

Spoiler: Catenary Sag Pull In - Theory

But therein is the key point - your explanation misses it.
With just 1% of sagging you trigger near the maximum amount of inwards pulling. Hence the need to understand the vectors. Free of the focus on all the other issues. The angle of the applied vector is what matters. IF the sagging resulted in a 45-degree downwards slope of the applied force the "down" force remains constant. The pull vector becomes 1/sin45degrees == 1.414.
Here is a very crude graphic that should help for now:

If we apply a load of 2 at the midpoint AND it results in a 45 degree slope of the sagging joist then:
(a) The downward load of 2 is shared equally 1 to each side of the sagging joist.

(b) That downwards weight force is resisted by the upwards tension force in the sloping member. And to produce 1 vertical uplift means 1.414 tension is applied in the joist - BTW that is true whether it is an elastic sagging beam OR a catenary rope.
AND
(c) That same 1.414 tension is resisted by the column. It exerts a 1.0 inwards pull - shown as the pull on the column of 1.0 inwards. (There is also a pull vector of 1.0 downwards exerted on the columns - you have already shown an understanding of that part of the analysis.)(And the vector reality is inexorably locked into the geometry of the situation. The weight of 2x1 is fixed. And to hold up the resulting 1 on each side MUST have a force of 1.414 tension in the sloping rope or sagging beam.)

My involvement in discussion of the factor was originally on JREF. In a comment to Tony Szamboti I mentioned, in passing, that "Catenary pull in is a very effective force multiplier". Tony accepted it as an obvious comment but we were flooded by disagreements from other debunker types. I made a snide comment that my grandson would understand the concept.

A few days later I conducted an experiment starring the grandson - at that time he was 6yo. Now 18.

I re-posted that experiment in the same DM discussion. Quoted below under spoiler.

Spoiler: Catenary Sag Pull In - Experiment

Just for possible interest. I've lost sign-on at JREF/ISF due to a change of email - a long story. So I cannot at present search for my original post. However, I found a reference to my "experiment" here on Metabunk. It demonstrates how catenary sag can cause large force multiplication. Here it is - semi light-hearted:

https://www.metabunk.org/threads/the-pre-collapse-inward-bowing-of-wtc2.4760/page-4



The challenge for most models is to get them close enough for the target audience to translate model>>reality. Not easy when the target audience includes people who cannot visualise the situation in the first place.

This is the "catenary pull in" model and experiment I conducted:

The "quantified" results:
1) One 6yo boy push at centre of rope caused 90-100mm IB of the far 'Perimeter Column'
2) The same 6yo push applied directly to the 'perimeter column' produced no measurable deflection.

The results confirmed by interview of the leading participant. With a language concession changing 'perimeter column' to 'tree' given the age and vocabulary limitations of said participant.
Even translating from horizontal to vertical mode caused some persons confusion. Those who originally disagreed counter claimed that the experiment was 'childish' and ignored that it proved the point.

Translate from horizontal to vertical and, experimental version, one 6yo boy pushing at the centre of the catenary achieved 4 inches "inwards bowing" of the perimeter column (tree). The boy could not achieve the same 4 inch deflection when pushing directly on the tree.

In the real WTC collapse event the observed sag of overheated joists was 10 or 20% of span. With 20% sag the pull-in could reach 5 times multiplication of the floor weight download. (At the temperatures experienced, the stiffness i.e bending moment resistance would be insignificant. The joist failed in bending but still retaining strength in tension.)

 

[MapperGuy]

Take care - there are a few assumptions developing in recent posts. First a presumption that dropping floors was the initiating factor. Possibly a consequence of the lack of clarity of the Kostack visualisation.

For the real event there is strong visual evidence that sagging of overheated floor joists caused the initial pull in of the perimeter columns. The effect is a result of the geometry of a catenary. Explanation will follow. Catenary sag pull-in has been the accepted wisdom for many years.

Bottom line is that catenary sagging can cause inwards pulling which can be, almost certainly is, many times the magnitude of the downwards force from the weight of the floor.

Therefore, the first of these assertions is not true for the real event.


Here is the explanation of the theory. It comes from a conversion several of us had b DM on one of those multiple previous discussions when the main thread was closed by moderation. (Participants Scaramanga, Mendel, econ41. Circa October 2023)

My involvement in discussion of the factor was originally on JREF. In a comment to Tony Szamboti I mentioned, in passing, that "Catenary pull in is a very effective force multiplier". Tony accepted it as an obvious comment but we were flooded by disagreements from other debunker types. I made a snide comment that my grandson would understand the concept.

A few days later I conducted an experiment starring the grandson - at that time he was 6yo. Now 18.

I re-posted that experiment in the same DM discussion. Quoted below under spoiler.

Spoiler: Catenary Sag Pull In - Experiment

Just for possible interest. I've lost sign-on at JREF/ISF due to a change of email - a long story. So I cannot at present search for my original post. However, I found a reference to my "experiment" here on Metabunk. It demonstrates how catenary sag can cause large force multiplication. Here it is - semi light-hearted:

Translate from horizontal to vertical and, experimental version, one 6yo boy pushing at the centre of the catenary achieved 4 inches "inwards bowing" of the perimeter column (tree). The boy could not achieve the same 4 inch deflection when pushing directly on the tree.

In the real WTC collapse event the observed sag of overheated joists was 10 or 20% of span. With 20% sag the pull-in could reach 5 times multiplication of the floor weight download. (At the temperatures experienced, the stiffness i.e bending moment resistance would be insignificant. The joist failed in bending but still retaining strength in tension.)

This is all very interesting, but getting down into the weeds can cause people to loose sight of the bigger picture.
The details here can be argued obviously, but the 9/11 Truthers alternative is the presence of a large number of demolition charges were responsible for the deliberate collapse of the towers.
Does anything in the simulation show the need for sequential explosions taking place, or simultaneous explosions creating/initiating this collapse?

 

[econ41]

This is all very interesting, but getting down into the weeds can cause people to loose sight of the bigger picture.

Yes. A continuing risk. There are multiple examples in this thread and several previous threads involving discussions with Thomas B.

In fact this proximate need for detailed explanation is unusual for me - I'm usually the one addressing the need to look at a "bigger picture". And not always the complete overall picture. Often just the legitimate context for the bit of the picture in contemporary discussion.

On this occasion, we are seeing intrusion of a false detail which doesn't fit a legitimate "big picture"

The details here can be argued obviously, but the 9/11 Truthers alternative is the presence of a large number of demolition charges were responsible for the deliberate collapse of the towers.

Sure, but that is way off-topic. HOWEVER, let's look at it from a "bigger picture" perspective.
The Top Level perspective is not even technical. There have been many claims for explosive CD.

Top Level:
(1) No claim has ever presented a prima facie case that explosives were needed. There have been multiple explanation of the causes and mechanisms of the collapses. Different in detail, agreed the common theme including "there was no need for explosive help".
(2) No claim has ever presented "proof" - in the form of a reasoned prima facie hypothesis - that Explosive CD was performed. AND
(3) No claim has ever presented a plausible hypothesis showing how explosive CD could produce the collapse mechanisms seen on 9/11.

Next level down - the collapses of the Twin Towers clearly fall into two stages viz something that dropped the top block then something caused the rapid global collapse. N o claimant I am aware o has ever attempted to define those two distinct stages and different mechanisms.

More details. This is where most claims fit. The one relative to this Kostack model are those claiming"squibs". i.e. spurts of dust observed tracking the collapse have been claimed as practiced and necessary to disconnect the floor joists from the perimeter columns.

Each of those multiple "bits of claims" needs addressing - and has been addressed with the relevant arguments.

But the "big picture" relevance is - if the bit of partial claim cannot be fitted legitmately into the "big picture" the "bit" of claim is not legitmately supported. The case is "not made out". It is probsaly but not necessarily false.

I'll leave my comments about big or little picture there.

Does anything in the simulation show the need for sequential explosions taking place, or simultaneous explosions creating/initiating this collapse?

No. And it seems to start with multiple floors collapsing onto lower floors therby overloading the lower floors. v That much is OK EXCEPT the first to fall, at least for WTC2, resulted from catenary sagging as per my previous post explanation.

That trigger, floor joist catenary sagging pull in for WTC2,***>>> started perimeter column inward bowing >>> In turn causing compresive axial failure of perimeter columns due to the resutlting eecentric loading >>>. And the failure of those perimeter columns in turn started the sequenced cascading failure of multiple columns until there was not enough remaining strength to support the Top Block which then ran away. Progression to global collapse.

And that last paragrph is the style of comprehensive fitting to context which is needed to legitmately fit the "big picture". Three levels of linkage in that example.
.
.
*** And "floor joist catenary sagging pull in for WTC2," is the detail bit that I explained, linked by four steps to the relevant big picture.

 

[Mendel]

Bottom line is that catenary sagging can cause inwards pulling which can be, almost certainly is, many times the magnitude of the downwards force from the weight of the floor.

In the rigid state, the floor exerts no inward pull.
In a fully flexible state, it forms a catenary. But the transition is not instantaneous, and the floor will still deform or break under sufficient tension, which puts an upper limit on the force.

 

[econ41]

In the rigid state, the floor exerts no inward pull.

Yes. But the discussion is about triggering failure.

In a fully flexible state, it forms a catenary.

That is the observed mechanism for a couple of joists in the real event WTC2 initiation, leading to perimeter inwards bowing. Not shown by Kostack.

But the transition is not instantaneous,

.. and?

and the floor will still deform or break under sufficient tension, which puts an upper limit on the force.

Yes. Hence, the many errant discussions I referred to from previous years and on other forms. (JREF, The911Forum)

The "weak link" for pull in tension is the joist to perimeter connection. Even heated the tensile strength of the floor joist members still exceeds the strength of the column connection.

One of two reasons why catenary sag could not cause the full limit ~50 inches observed. Catenary sag only starts the bowing. Self load "eccentricity" continues the bowing. Plus, strength aside, catenary sag cannot achieve the 50 inch pull distance. I can't remember the limit without searching JREF/ISF.