psikeyhackr
Member
Then why wasn't there lots of core still standing when time was all over?
How high could the plane have hit, and still caused a total collapse?
- Thread starter Henkka
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Mendel
Senior Member.
But there was!
I've linked to the "spire" earlier in the thread, but it's apparently not enough to just link it:
You can clearly see that much of the core remained standing after the floors were already gone, and the facade had fallen down.
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Good question. That's because they fell over. This occurred with a delay. @Mendel has provided some if the evidence; here is some more
https://www.quora.com/What-is-your-...share=4fc39335&srid=u0gO1B&target_type=answer
From the source
>The pancaking left the walls around the building standing. They then gradually toppled outward.
>Here are two GIFs which illustrate this well. Notice how the last pieces of debris appear to start from roughly the same places as the first, near where the top of the tower used to be. But these later pieces are moving further out, suggesting that they are being "thrown".
>These GIFs start around 1–2 seconds into the collapse, and last 11 seconds ie:; until pancaking is complete.
Mendel
Senior Member.
They solve the wind problem in different ways.
The Eiffel tower has enough rigidity to not bend.
The WTC frame, braced by the floors, is rigid in a different way. If you topple a cardboard box, you need to lift one side up if you can't destroy the box; that's how the "facade box" of the WTC towers worked. If wind tries to topple the tower, the weight on the side that would have to lift off keeps it stable, and these forces are distributed across almost the whole height.
Jeffrey Orling
Senior Member
The total collapse was caused by perhaps 5 or 6 floors crashing down causing a runaway floor collapse (whatever exceeded the design capacity of a typical twin tower slab). The exterior was unstable without the bracing the floor slabs provided. Column free office space designs are vulnerable to pancaking runaway floor collapse / total destruction.
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Yeah this number of around 5 to 6 floors causing total collapse has been mentioned earlier in this thread also. Based on that, I went to Photoshop to create another illustration of this idea. Let's imagine the top 5-6 floors of either tower are lifted up about one floor by a giant crane:
So if we then cut the cord and let the top fall, we should get a collapse that accelerates all the way to the ground, yeah? And leaves just a ribble pile looking like this:
That's what would happen if the cord was cut, in your opinion?
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Jeffrey Orling
Senior Member
yes
Mendel
Senior Member.
You'd have to move it sideways a few feet such that the columns no longer align. (see @econ41's picture in post #64.) You need the core and facade in your crane block to fall together with the floors, and if they align with the lower parts of those columns, that won't happen. But that's getting into collapse initiation, which comes before progression.
If you had a demolition team rig each and every floor-column connection on these top 6 floors with a small charge that destroys the bolt, such that you could detach these floors at the push of a button, leaving all the columns intact, you'd be able to cause total collapse. The 6 floors crashing down would suffice. (What actually happened was for enough core columns to lose strength from the heat.)
Jeffrey Orling
Senior Member
Why do you have to blow up ALL the connections? How about just over half or 60%
econ41
Senior Member
Are you aware that you are circling this discussion back to issues and confusions that dominated debate circa 2005-6-7-8-9?
The "one-floor drop" scenario was the one proposed by Bazant & Zhou back in their limit case paper of 2001-2. It led to a lot of confusion...
It depends on who you believe and whether or not your "falling top block" lands with all columns aligned on the lower tower. Two distinct scenarios - one of them with divergent analyses:
1) If the Top Block "drops" and the columns are NOT aligned.....YES - global collapse to ground level would follow.
2) IF the "Top Block" impacts with column ends aligned you face two different assessments.
(a) Bazant & Zhou 2001-2 said "Yes - there is more than sufficient energy to cause global collapse to ground level by the mechanism of column buckling".
(b) Szuladzinski, Szamboti and Johns, in 2013, said: "Bazant got his sums wrong - there wasn't enough energy - it would arrest" https://www.ae911truth.org/images/PDFs/Szuladzinski.Johns.Szamboti.pdf
If the column ends missed >> Global Collapse;
If the column ends hit in alignment >> collapse would start and arrest after a few stories. (I think Bazant was wrong , Szuladzinski et al were right. ON THAT PART of their claim.
)
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Mendel
Senior Member.
Simplicity. Since the question was about progression.
a "few storeys" of rubble ought to be enough to start ROOSD
from @Abdullah 's link:
Article: Here is the design live load of a typical Tower floor.
The typical floor had a 4 inch concrete slab. This alone would contribute 40–70psf per additional floor. So 2–3 additional floors coming to rest on top is dangerous.
Once you overload a corner, and break its supports, load redistribution would overload the other connections as well, it would rip off like toilet paper. Assuming a 2x safety factor design, 2-3 floors worth of rubble can do that, if the outward pressure from it doesn't simply push the facade off.
econ41
Senior Member
Except where does the rubble come from in the simplified model we are discussing? IF the impact was sufficient to shear off the bottom couple of Top Block floors >> maybe.
We are getting deep into speculation for a simplistic model which is not possible. Many years ago when this topic was under active discussion - I parodied the rebuttal because of the impossible crane size. And there are more rigorous ways to falsify the claims but.....
Mendel
Senior Member.
from your "few storeys" of collapse, sometimes termed "crush-down".
In the Bazant model, the top moves downwards because some storeys between the top and the bottom get completely crushed, which makes them rubble.
You described this (and I quoted you) as "collapse would start and arrest after a few stories".
However, that's not the point. Thinking about progression, we're looking for a simplified initiation model here; and we have evidence that the columns did not align.
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econ41
Senior Member
A good point. Worthy of speculation and I hadn't considered it. My focus was on the historic arguments pro and anti Bazant. The Henka proposal is the hypothetical startup of the Bazant CD/CU model. (The concept of "dropping the top block" from Bazant & Zhou 2001-2 where it was framed legitimately as a "limit case" example. "CD/CU" originated with Bazant & Verdure 2007 where Bazant actually fell for the trap he set in B&Z 2001-2 - a story for another time.
)The Bazant CD/CU hypothesis is false for WTC towers - impossible to "set up" - therefore I halted my speculation. Your comment is plausible if, for moot purposes, we assume the model could be set-up. The storeys that are crushed in the Bazant CD/CU model are the top ones of the lower tower at any stage. Specifically, they are NOT the underside of the Top Block. In CD/CU the Top Block remains intact all the way to the bottom. In reality, the Top Block broke up concurrently with more or less the same number of storeys at the top of the lower tower - as per that diagram I posted a couple of times.
Yes - that is the Szuladzinski, Szamboti and Johns conclusion. Based on their estimate of the weight of Top Block and their finding that Bazants estimate was wrong. Over optimistic. That aspect of their paper has never AFAIK been rebutted by professionals - presumably because it is a "truther" paper. I have no problem accepting truther findings when they are correct.
I addressed both "aligned" and "not aligned". I'm sure that progression would not halt in the not aligned or ROOSD scenario.
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Jeffrey Orling
Senior Member
The ROOSED mechanism is really basic settled engineering - severely over load a floor and it braked apart/shatters/ fails. It certainly seems implausible that slab could maintain its integrity while overloaded its connection to the axial structures. (didn't happen)
The "issue" has always been how did non fatal mechanical damage from the plane strike... plus extensive unfought fires get the ROOSD "going"... the so call "initiation phase"? It seems plausible that there was loss of axial capacity which led to "things" falling... (the top block) as whole, or "in part". My thinking is that the top's lost integrity.... parts of them drooped (slabs), some maintained integrity - "shell", some a little of both - hat truss and antenna.
I suspect the effect of heat was mostly to warp, expand, weaken lateral elements which could cause interruption of the transfer of floor loads to the columns. If the columns or connections to them were non performing... the slab, without support would collapse locally.... and that would rapidly spread to involve more floor area.
It appears that the all 3 towers experienced a sort of ROOSD and all the began with overheated lateral steel "messing with" the integrity of the frame.
In the case of 7WTC, the lateral steel around col 79, 80 and 81 failed and led to local floor collapsed which went ROOSD that collapse likely caused axial structure and transfer trusses to fail which involved the entire footprint and undermined the support of the moment frame.
In the case of the twins heat expanded steel caused asymmetrical lateral displacement leading to displacement and tipping of the perimeter and more. ROOSD is unstoppable because the structures are not designed to arrest this level of "over loading".
The "issue" has always been how did non fatal mechanical damage from the plane strike... plus extensive unfought fires get the ROOSD "going"... the so call "initiation phase"? It seems plausible that there was loss of axial capacity which led to "things" falling... (the top block) as whole, or "in part". My thinking is that the top's lost integrity.... parts of them drooped (slabs), some maintained integrity - "shell", some a little of both - hat truss and antenna.
I suspect the effect of heat was mostly to warp, expand, weaken lateral elements which could cause interruption of the transfer of floor loads to the columns. If the columns or connections to them were non performing... the slab, without support would collapse locally.... and that would rapidly spread to involve more floor area.
It appears that the all 3 towers experienced a sort of ROOSD and all the began with overheated lateral steel "messing with" the integrity of the frame.
In the case of 7WTC, the lateral steel around col 79, 80 and 81 failed and led to local floor collapsed which went ROOSD that collapse likely caused axial structure and transfer trusses to fail which involved the entire footprint and undermined the support of the moment frame.
In the case of the twins heat expanded steel caused asymmetrical lateral displacement leading to displacement and tipping of the perimeter and more. ROOSD is unstoppable because the structures are not designed to arrest this level of "over loading".
ROOSD isn't the accepted, mainstream explanation though. Bazant's "Crush-down, crush-up" is. You would think someone would try to correct the record on this. I know Szamboti has been trying to publish a critique of Bazant for like 10 years without success haha.
How do you figure they missed? Just looking at it, it's kind of hard to imagine the collapse being more "straight down" than it was:If the column ends missed >> Global Collapse;
If the column ends hit in alignment >> collapse would start and arrest after a few stories. (I think Bazant was wrong , Szuladzinski et al were right. ON THAT PART of their claim.
Source: https://www.youtube.com/watch?v=xGAofwkAOlo
Jeffrey Orling
Senior Member
Mendel
Senior Member.
I'm not sure this is a good view point to see the tilt.
How does Bazant explain the spire? and the long slabs of facade lying uncrushed on the ground afterwards?
The point is —and NIST FAQ #18 acknowledges this— that the main mechanism of the collapse progression is the floors falling down.
I think if you can unbalance something like the top 2 floors by pushing an airliner through the facade on most of the core, so that the outer wall kind of pivots down and hits the lower slab nesr the edge, the edge connections would be ripped apart, and then the whole floor would tilt and rip out of its moorings, and then we'd have a somewhat diagonal collapse front going down the building. But you'd really want to simulate it to be sure.
Jeffrey Orling
Senior Member
Bazant does not describe the collapse of the twin towers. His work amounts to theoretical navel gazing.
econ41
Senior Member
Actually the issue of columns aligned or not aligned is a central factor in the applied physics needed to answer the OP question. BUT a definitive answer almost certainly would need a quantified and comprehensive engineering assessment which I don't think we have the skills or the resources to apply in this medium of on-line forum discussion. The best we can achieve is a somewhat subjective guesstimate concluding: "A higher hit by the plane could probably have resulted in the same collapse mechanism but we cannot be sure how much higher." AND "It may be possible that a higher impact could trigger a different collapse mechanism but we cannot define what form such a mechanism would take."
Current discussion is about that issue of "columns aligned or not aligned" - a topic that has been a major point of confusion throughout the history of discussion of WTC collapses. Academic and professional formal debate mostly occurred in the era 2001 thru 2008 and was based on assumptions of "columns aligned". Informal debate on this and similar high level forums has progressed further and has recognised that columns NOT aligned was the true mechanism.
I and one or two other members have recogised the importance of the issue. Other members are still coming to grips with it. But I suggest understanding the issue "columns aligned or not aligned" is an essential step in forming a reasoned support for an answer to the OP question.
My apology for presenting the explanation as "informed opinion" - without the rigour of full reasoning with evidence and citations.
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econ41
Senior Member
You are a perennial optimist @Jeffrey. Have you tried to get any member to explicitly agree with "ROOSD"?
That is a better assessment. And, as far as I am aware, I'm one of few who are bold enough to disagree with Bazant AND partially agree with Szamboti et al. Bazant and Verdure's "CD/CU" hypothesis is not possible for WTC Twin Towers. There are four fatal reasons. Three of them independently fatal. And I doubt you will find another debunker who will agree to that bold statement.
Szamboti's attempts are also down a false trail. Bazant & Zhou 2001-2 was correct but led to misunderstandings. Szamboti and many others misunderstood. Then Bazant & Verdure in 2007 made the same mistake leading to "CD/CU". The same underlying error >> failure to understand the actual mechanism of collapse. Relying instead on 1D approximations and/or false assumptions about the issue of column alignment. This is why this discussion is still relevant to the OP. Whether or not the column ends remained aligned and impacted OR missed and bypassed is of fundamental importance to the OP question.
It is relatively easy to demonstrate why columns could not and did not remain aligned. Also why column ends did and must have "missed" or "bypassed".
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econ41
Senior Member
He doesn't. Despite the high regard he is given he has not done much to advance understanding of WTC collapses. His first paper with Zhou 2001-2 caused a lot of misunderstanding tho correct itself. Then his hypothesis with Verdure 2007 which postulates "Crush Down/Crush Up" I contend is wrong - fatally flawed as an explanation of WTC collapses. But few are prepared to agree with me because most debunkers seem to assume that both NIST and Bazant are infallible. I don 't agree.
Further explanation would go too far off topic in my opinion.
psikeyhackr
Member
Curious how we can supposedly simulate the climate of a planet 8,000 miles in diameter for the next 80 years but cannot do it for the collapse of a skyscraper that took less than a minute.
How could the simulation be made without accurate data on all of the columns and beams?
With a good simulation the falling top could be moved into any position and tested to see if any orientation could cause complete collapse.
How could the simulation be made without accurate data on all of the columns and beams?
With a good simulation the falling top could be moved into any position and tested to see if any orientation could cause complete collapse.
Mendel
Senior Member.
these simulations are made the same way climate simulations are made: with reasonable assumptions about the range of the unknown values. In case of the WTC, we have accurate data on the beams and columns; we lack accurate data on the damage they sustained, and the collapse sequence, but a range of possible scenarios simulated all support the same conclusion.
Source: https://esd.copernicus.org/articles/12/545/2021/The problem you're going to encounter with the question of the topic is that engineering software (finite elements analysis) is geared towards analysing forces in intact structures, and not designed to simulate ad-hoc forces such as rubble crashing into a floor below. It works great to analyse what leads up to a break, but can't easily tell you what happened afterwards.
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Jeffrey Orling
Senior Member
The collapse can be simulated.
The ROOSD phase is well understood.
The initiation seems to involve lost of axial capacity from columns ends being pushed to misalign, lose bearing and buckle. There loads were handed off to other columns which became over loaded. There was an at first slow load distribution which increased in rate and then the top's lost adequate support to remain and so they dropped and being mis aligned.... and kicked off ROOSD.
The ROOSD phase is well understood.
The initiation seems to involve lost of axial capacity from columns ends being pushed to misalign, lose bearing and buckle. There loads were handed off to other columns which became over loaded. There was an at first slow load distribution which increased in rate and then the top's lost adequate support to remain and so they dropped and being mis aligned.... and kicked off ROOSD.
@psikeyhackr what makes you think we can't?
In any case, ROOSD is fairly insensitive to errors - particularly in column modeling.
In any case, ROOSD is fairly insensitive to errors - particularly in column modeling.
Well, it's been 20 years and afaik no university or research group has done a simulation replicating the total collapse of the towers. Which is a bit strange, considering it is the most shocking and historically significant engineering failure ever. Kai Kostack is doing one, but I think it's just a personal project?
Although you wouldn't even have to simulate the total collapse to settle the Bazant Vs. Szamboti question. Just simulate the very beginning, and see if you can match it to the smooth descent seen in the Sauret footage. If it decelerates and stops, Szamboti is right. If not, Bazant. With a computer simulation, you could also investigate the question of how high the plane needed to hit to cause total collapse.
Although you wouldn't even have to simulate the total collapse to settle the Bazant Vs. Szamboti question. Just simulate the very beginning, and see if you can match it to the smooth descent seen in the Sauret footage. If it decelerates and stops, Szamboti is right. If not, Bazant. With a computer simulation, you could also investigate the question of how high the plane needed to hit to cause total collapse.
Jeffrey Orling
Senior Member
Purdue University did a sim.
The collapses have a min of two phases ( with transitions from one to the next.
ROOSD is basically what happens when a floor slab is overloaded (dynamically I might add)....It collapses, shatters is destroyed... most likely in parts but involving entire floor footprint. This is settle basic engineering.
The initiation phase involved the "creation" or freeing from the structure... the mass which starts the runaway collapse.
So... the initiation phase causes were the initial mechanical damage/frame destruction from the plane strikes AND the subsequent destruction the heat from fires did to the frame. The unfought fires led to warping, weakening, and lengthening of lateral steel. This led to lateral displacement of core columns enough to cause their end to end connections to misalign and "fail". One by one the columns "offloaded" the load they carried to adjacent columns and this drove down and eventually destroyed axial capacity such that they failed and the top blocks has inadequate support and dropped.
We can only guess at the sequence because we can't see inside to the core. Econ's diagram explains the process. It's obvious that there was some asymmetry in play which led to the top tipping and lateral translation as it fell. The hat trusses and floor slabs may have held the top blocks together even as support was lost and the fell. But fell it did and this was more than enough mass to cause a ROOSD - runaway collapse of the floors
Please include the text, in quotes, of the message you are responding to.
Mendel
Senior Member.
No.
It's a demonstrator for his "Bullet Constraints Builder for Blender"., and that project is connected to the The Finnish Laurea University of Applied Sciences. See https://www.metabunk.org/threads/how-could-the-planes-wings-penetrate-the-wtc.3326/post-259678
The project is unfinished, though, and remains unvalidated.
Of the plane impact yeah, but not of the collapse. Unless I'm mistaken.
Okay, good to know... But you probably understand what I mean. That it's seemingly a project made by one guy, using a program that is not specifically designed for engineering simulations (Blender). I would like to see something similar to the NIST sim of WTC7, meaning a team of professional engineers with a sizeable budget doing a simulation with software like LSDYNA/ANSYS.
Nor has anyone offered a demonstration model of the basic and general principles. The OP asks, "How high could the plane have hit?" It's a good simple question and the answer would help us to understand the process.
But I don't think anyone here (or anyone employed at any university) is able to describe with math a simple four-column model that would totally collapse if hit at one height and not at some other height.
If anyone here can, or knows of someone who can, please let us know.
Jeffrey Orling
Senior Member
Irrelevant
The runaway floor collapse was from overloaded floors sequentially collapsing from the plane strike zone down"
THAT happened because the top lost axial support and dropped done (and tilted) at the level of the plane strike
Initial plane damage itself was not enough to cause the tops to drop. That happened be HEAT messed with the frame up there.
econ41
Senior Member
Actually, it is even simpler than that. The apparent "Bazant v Szamboti" difference is a matter of simple logic. False assumptions about starting premises. And, yes, a lot of people misunderstood the central issues:
1) The Bazant & Zhou paper of 2001-2 was a simple limit case analysis. It made two assumptions viz (a) That the Top Block somehow "dropped" onto the lower tower AND (b) landed with the columns of the Top Block aligned with those of the lower Tower. THEREFORE the lower tower presented the greatest possible resistance to collapse. THEREFORE it was a "limit case" - the best case for survival but B&Z found that there was sufficient energy to result in global collapse even in that "best case for survival". BUT the "drop to impact" scenario was not the real situation. It never happened that way.
2) Tony Szamboti assumed that the B&Z "limit case" was what literally happened - including the two assumptions viz: (a) "Drop to impact"; and (b) "With column ends aligned". So he went looking at the motions to identify the "jolt" which should have occurred when the impact occurred. He wrote a paper, co-authored with Graeme MacQueen, "The Missing Jolt: A Simple Refutation of the NIST-Bazant Collapse Hypothesis". They found that there was no jolt and therefore concluded that Bazant was wrong. Followed by the false dichotomy which was to become a Trademark of Tony's writing. viz "I've proved xyz was wrong THEREFORE I am right".
So resolving the difference "Bazant v Szamboti" doesn't need simulation - the error is in the specification of the problem and Tony's main error of taking an abstract never happened limit case demonstration as if it literally happened. << THAT was his #1 mistake. Most debunkers slowly came to recognise that one. However his second mistake has survived, generally unrecognised. The assumption also derived from B&Z that the Top Block dropped to impact. Many hours and megabytes of writing have been spent analysing the "Missing Jolt". It wasn't "Missing" it simply never was. There was never a "drop to impact" scenario. Fuller explanation available if anyone is interested in the context of this thread's topic..
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So, hold on... If NIST didn't investigate the collapses beyond initiation, and Bazant's study is just an "abstract never happened limit case demonstration", does that mean there is no mainstream explanation for the total collapse of the towers, 20 years after the event?
econ41
Senior Member
NIST, in meeting its statutory obligation, concluded that (my words) "once the collapse was initiated global progression was inevitable". NIST met the statutory requirement to the implicit satisfaction of the authority which imposed the obligation. The US Government. NIST was NOT tasked with satisfying all the concerns, real or imaginary, of ordinary citizenry including the fringe of conspiracy theorists.
Bazant's study has no place in the formal processes of Government investigation and explanation.
Define what you mean by "mainstream", for whom it provides explanations and identify what basis, if any, there is for needing more "explanation".
Many interested parties have discussed and explained the WTC collapses in varying depths of detail and with widely differing levels of scientific accuracy. What more do you think is needed? And why?
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Mendel
Senior Member.
could you please stop trying to manufacture scandal? NIST FAQ #18 has been quoted here more often than I can count. It's so obvious that it does not require simulation, because the overload factor is already so great at this point.
We're also getting to the same point we were at for WTC7: the CD theory covers the initiation (which NIST examined), the subsequent collapse would look the same no matter what initiated it: the "missing explanation" is the same in both scenarios.
Well, I just mean an explanation of the collapse that is universally agreed upon by experts, and presented to the public. So if I look up why the Tacoma bridge collapsed on Wikipedia for example, it gives me what I would consider to be the "mainstream" explanation. But if I look up why the WTC towers collapsed, it gives me the Bazant story, which you yourself say "never happened", and in general is rife with problems.Define what you mean by "mainstream", for whom it provides explanations and identify what basis, if any, there is for needing more "explanation".
Many interested parties have discussed and explained the WTC collapses in varying depths of detail and with widely differing levels of scientific accuracy. What more do you think is needed? And why?
You guys seem to prefer this ROOSD thing, but to be frank, it doesn't seem to have much scientific backing and exists only on obscure internet forums like this one.
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