Why?
Would the WTC Twin Towers have collapsed from fire alone, without plane impact?
- Thread starter econ41
- Start date
Jeffrey Orling
Senior Member
first of all it would only "pull in" opposite the core... corners would / could not be pulled in Do you think pull in on one short or long side would cause the entire perimeter to then buckle?
Maybe. If the wall buckled Why do you think it can't?
Jeffrey Orling
Senior Member
not enough axial capacity would be lost.
Yep. But that can change when you consider the effect of the floor area settling/collapsing with the buckled wall. This would leave parts of adjacent walls unbraced.
Add to this the dynamic amplification from the sudden displacement
Oystein
Senior Member
13,227 pounds of explosives were used to demolish the Mina Plaza in UAE:
Source: https://www.youtube.com/watch?v=5ceXT5PYTGI
https://interestingengineering.com/...zas-demolished-in-abu-dhabi-within-10-seconds
And of course, they were also "smartly placed" by demolition professionals. But for this:
Eh, 75 pounds should suffice.
More incredulity, still no argument.
I did: steel.
Go with NIST's back-of-the-envelope calculation. Make each floor able to carry the weight of 11 additional floors.
@Jeffrey Orling here is the math.
-Normal utilisation factor of walls is 20%.
-12,000kip reduction for hatbtruss gives 13% above FL98
-loss of one wall ups that to 26%.
-dynamic amplification ups that to 52%
-loss of 24% of adjacent walls ups that to 100%
-Normal utilisation factor of walls is 20%.
-12,000kip reduction for hatbtruss gives 13% above FL98
-loss of one wall ups that to 26%.
-dynamic amplification ups that to 52%
-loss of 24% of adjacent walls ups that to 100%
benthamitemetric
Senior Member
Ok, let me whip out my finite element software to model the propensity to buckle of an arbitrarily large and thick steel pipe that is impossible to construct and has no relevance to this conversation. Please just wait till I'm done to comment further. This may take a while.
Oystein
Senior Member
Why did you pick this example? Where not one but four buildings were demolished - all of them concrete structures?
You could just as well have picked the steel-frame Landmark Tower in Fort Worth, Texas, 30 floors and 120 meters (393 ft) high and demolished in 2006 with the use of merely 364 pounds of explosives: https://en.wikipedia.org/wiki/Landmark_Tower_(Fort_Worth,_Texas)#Abandonment_and_demolition
Ok, now you know that 364 pounds of explosives suffice to demolish some steel-frame skyscraper.
Let me guess: You think because another skyscraper has more floors and is taller, it would require more explosives, right?
Well, you would be wrong.
The taller a building is, the higher its center of gravity, which means the higher the specific potential energy against the gravitational field stored in its mass (by "specific" PE I mean the PE per mass unit).
This means, essentially, that the taller a building, the easier it is for it to crush itself. Just consider that the WTC fell from an average height of 560 feet, but the Landmark Tower only from an average height of 161 feet.
And keep in mind, do not forget, that the WTC twins had this vulnerability of wide open floor spaces which got smacked with a large proportion of the falling mass and were not nearly able to resist that mass and its momentum - the main collapse bypassed the columns almost entirely.
(In case you never knew, or have conveniently forgotten: The twin towers were 95% air, 98% of their footprint area was free of columns)
The Landmark used 364 pounds of explosives and not just 75 pounds at least in part to CONTROL the collapse - to direct the fall such that designated safe, clear areas were impacted. This requires MORE explosives than the bare minimum of "somehow" making them collapse.
--------------
So now, @Henkka you KNOW it realistically takes only on the order of 100 pounds to bring down a steel frame skyscraper.
And you have a plan how to cut the floor trusses of WTC1/2 with - rough estimate - 75 pounds.
What now? Which evasion will you try now? How else will you reword your bare, uneducated, uncomprehending incredulity?
Where is your ARGUMENT
And once more: Why did you happen to pick the Mina Plaza buildings implosion? Who told you of them?
Oystein
Senior Member
I am, unfortunately, a man who must work full time, sleep, eat and even socialize from time to time. And I cannot spend time on the internet while at work (I actually work all the time!).
So excuse my not having read even only nearly all posts, you guys are way too fast for me.
Has someone in the meantime explained to @Thomas B that the point about Verinage demolition typically being initiated at about half the height is pretty moot?
First of all, it's not even true. Take this compilation of a handful of Verinage demolitions, each time count the floors above and below the couple of floors that get jacked: Generally, the top is a bit shorter than the bottom. In the last example, starting at 3:30 min, the top is only a fraction of the bottom - and it still works (3 floors above; below is hard to count as the camera pans down unsteadily, but I think I count 10):
Source: https://www.youtube.com/watch?v=NwFHEoiUZ7o&t=210
I think much more important is the observation that it is almost always 6 floors on top! (With the exception of 3 floors in the last case)
The WTC twins had 12 and 28 floors on top coming down. That changes the math, doesn't it?
It has been pointed out at nauseam, but perhaps still not been understood by those who persist in not understanding, that of course the falling mass increases with every floor added to the debris layer, and that thus indeed a tower with a million wide-open office floors could and would get destroyed by 12 floors on top. Sheesh. As if the rubble and mass of 999,998 floors could be stopped by the 11th floor.
So excuse my not having read even only nearly all posts, you guys are way too fast for me.
Has someone in the meantime explained to @Thomas B that the point about Verinage demolition typically being initiated at about half the height is pretty moot?
First of all, it's not even true. Take this compilation of a handful of Verinage demolitions, each time count the floors above and below the couple of floors that get jacked: Generally, the top is a bit shorter than the bottom. In the last example, starting at 3:30 min, the top is only a fraction of the bottom - and it still works (3 floors above; below is hard to count as the camera pans down unsteadily, but I think I count 10):
Source: https://www.youtube.com/watch?v=NwFHEoiUZ7o&t=210
I think much more important is the observation that it is almost always 6 floors on top! (With the exception of 3 floors in the last case)
The WTC twins had 12 and 28 floors on top coming down. That changes the math, doesn't it?
It has been pointed out at nauseam, but perhaps still not been understood by those who persist in not understanding, that of course the falling mass increases with every floor added to the debris layer, and that thus indeed a tower with a million wide-open office floors could and would get destroyed by 12 floors on top. Sheesh. As if the rubble and mass of 999,998 floors could be stopped by the 11th floor.
Well, the Wiki page doesn't specify, but from looking at videos of the demolition I'm going to take a wild guess that a lot of the 364 pounds of explosives were used to cut all or most of the main vertical columns near the base of the building. There's tiny explosions running along the entire height of the tower, but at 0:17 you can clearly see the huge blast at the bottom which actually causes the building to start falling:
Source: https://www.youtube.com/watch?v=79sJ1bMR6VQ
So, it's basically a classic CD implosion. There's also this:
So this was a professional demolition, with months of prep work, where explosives were used to cut the supports at the bottom, of a much smaller building. What you're proposing to do is quite different, where 75 pounds of explosives would be used on a bunch of horizontal floor supports near the top of the tower, instead of on vertical columns near the base... So just to recap, you think you could demolish a building over three times larger than this, with a quarter of the explosives, by attacking horizontal beams at the top, and obviously without months of prep work since there was no such work done on the WTC towers prior to 9/11. All I can say is, good luck with that.
econ41
Senior Member
This thread is a Train Wreck!!
Several off-topic themes are being pursued. The one making most of the contributions to the derailing is @Henkka's theme which has "emerged" or "developed" into a discussion of a moot speculation about whether a WTC Twin Tower collapse could be initiated by "ROOSD" alone - without the aircraft impact, fires or the dropping of the top block. << Which has nothing to do with the topic of this thread. Should have its own thread. And @Henkka has been advised to OP a thread.
So I reviewd the series of posts leading to @Henkka's derail - just to see how much of the guilt I should carry for letting him runaway. Here is what happened:
That speculation is obviously of ZERO relevance to explaining the actual 9/11 collapses.. And the brief answer to @Henkka's speculation - IMNSHO is:
(1) Yes you could trigger a collapse by explosive separation of a sufficient number of floors.
(2) I'm unsure how many but it could be as few as ONE floor. More likely 2-3-4 and triggered simultaneously.
(3) The resulting collapse would in no way resemble the actual 9/11 collapses.
(4) It would do nothing to help understanding of the actual 9/11 collapses.
And:
(5) The idea could be subject of some interesting technical speculation.
BUT
(6) It does not warrant serious discussion in the context of "what happened on 9/11".
Several off-topic themes are being pursued. The one making most of the contributions to the derailing is @Henkka's theme which has "emerged" or "developed" into a discussion of a moot speculation about whether a WTC Twin Tower collapse could be initiated by "ROOSD" alone - without the aircraft impact, fires or the dropping of the top block. << Which has nothing to do with the topic of this thread. Should have its own thread. And @Henkka has been advised to OP a thread.
So I reviewd the series of posts leading to @Henkka's derail - just to see how much of the guilt I should carry for letting him runaway. Here is what happened:
No further "off-topic" than most of the discussion. BUT a new theme. I made what to me was - still is - the obvious response:
Henkka did not see the significance of my comment.
So, since the discussion was heading into a more complex and off topic debate I said:
@Henkka has not taken that advice. BUT starts to drift into his new sort of unformed "hypothesis":
I (correctly I think) spotted the coming derail. And stated the problem concisely:
henkka has since committed more fully to his "Drop the Towers by explosively initiating ROOSD".
That speculation is obviously of ZERO relevance to explaining the actual 9/11 collapses.. And the brief answer to @Henkka's speculation - IMNSHO is:
(1) Yes you could trigger a collapse by explosive separation of a sufficient number of floors.
(2) I'm unsure how many but it could be as few as ONE floor. More likely 2-3-4 and triggered simultaneously.
(3) The resulting collapse would in no way resemble the actual 9/11 collapses.
(4) It would do nothing to help understanding of the actual 9/11 collapses.
And:
(5) The idea could be subject of some interesting technical speculation.
BUT
(6) It does not warrant serious discussion in the context of "what happened on 9/11".
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econ41
Senior Member
You are not the only sinner. I've been less than rigorous myself on this thread as it gradually drifted of my OP which was response to your question:
A comprehensive response to that question of necessity requires an understanding of the actual collapse mechanisms. And some drift of topic into explaining the actual mechanisms has been necessary because of the limited understanding some members have of those real events.
But your original question clearly had in mind the actual form of collapse that happened on 9/11.
Your speculation about a "ROOSD ONLY" deliberate method of CD is technically interesting BUT of no relevance to the OP Topic.
And we - you and I - are not the only ones drifting off topic... your "ROOSD Only" speculation is worthy of a separate thread. Maybe not in the 9/11 sub-forum but that is a "call" for Admin or Moderator decision.
econ41
Senior Member
It wouldn't take any explosives because debris did it as shown in this graphic first posted in Nov 2007.So you could do a controlled demolition of the tower just by attacking these flimsy little things with explosives?
That doesn't look like it would take a powerful explosive to take out the connection. Cut the trusses on a couple floors to get the unstoppable cascade going, columns lose lateral support, and it's RIP World Trade Center. Doable?
Even the die hard Bazantophile Debunkers denied it at that time and for a couple of years.
BUT it is what happened.
Mendel
Senior Member.
I thought it did? why do you think it didn't?
do you think this thread is going better?
Mendel
Senior Member.
Scaling down does not work, because some properties scale linear, some quadratic, and some cubic.
A tube is stronger than a pane, that's why reservoir dams are constructed curved.
Bolted connections are weaker than forged steel.
And if you apply outward pressure from inside a rectangular tube, it will want expand into a circle (likely breaking the connections) because that's the most area for the circumference; a circle will just stay round.
I'm sure if you had floors between your pipe-in-pipe, you could get them to ROOSD. You may or may not get the pressure from the debris to destroy the pipe where it could help destroy the WTC facade?
I'm not even sure that your one-foot thick, 200 feet wide, 1000 feet tall pipe wouldn't collapse on itself, or how thin you'd need to make its wall to insure collapse in a moderate breeze.
Oh, and you can drop a square lid into a square hole, but you can't drop a round lid into a round hole. That impacts your "impalement" scenario.
Mendel
Senior Member.
WTC1 was 1360 ft tall, 208×208 ft = 43264 ft²
Your pipe is short and only has 31426 ft².
Pretty sure your pipe would collapse if made from 3" steel.Fire Technology, doi:10.1007/s10694-012-0285-6.
Overview of the Structural Design of World Trade Center 1, 2, and 7 Buildings
Each column on floor 10 to 107 was fabricated by welding four steel plates to form a tall box, nominally 0.36 m (14 in) on a side. The space between the steel columns was 0.66 m (26 in), with a framed plate glass window in each gap. Adjacent columns were connected at each floor by steel spandrel plates, 1.3 m (52 in) high. The upper parts of the buildings had less wind load and building mass to support. Thus, on higher floors, the thickness of the steel plates making up the columns decreased, becoming as thin as 6 mm (¼ in) near the top down from as thick as 76 mm (3 in) at the lower floors. There were 10 grades of steel used for the columns and spandrels, with yield strengths ranging from 248 MPa (36 ksi) to 690 MPa (100 ksi). The grade of steel used in each location was dictated by the calculated stresses due to the gravity and wind loads. All the exterior columns and spandrels were prefabricated into welded panels, three stories tall and three columns wide. The panels, each numbered to identify its location in the tower, were then bolted to adjacent units to form the walls (Figure 4). Field panels were staggered so that every third panel was spliced at each floor level. The use of identically shaped prefabricated elements was an innovation that enabled rapid construction.
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econ41
Senior Member
@Jeffrey Orling also has some credibly plausible alternate explanations but all of them are far from supported by hypotheses.
In this case he pushes his own "belief" in a core-led collapse. THEN he denigrates/dismisses the other viable hypothesis (i.e. "perimeter led") by constructing his own strawman.
The reality is that the "initiation stage" of the Twin Towers' collapses was driven by a cascading failure of columns. Explained many times. And a cascading failure does NOT require all elements to fail at once. It results from a "trigger".
So a few perimeter columns "pulled in" would weaken those columns sufficiently to trigger a cascading failure. Both of those two assertions are readily supportable if they are not self-evident.
Sure we need to prove that such is what happened. And the proof can be mathematical - show that there was enough. OR the proof can be logical - show that there is no other option. So, by the scientific method, until someone shows there is another option "Perimeter was partially pulled in and the partial pull in was a trigger to the observed cascading failure" is the extant hypotheses in this discussion >> Twin Towers initiation explained AND global collapse ensued by global progression. And @Jeffrey Orling to support his claim needs to prove my assertion wrong. "Falsify" it if we want to be pedantic scientists.
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I like the idea of using the actual thickness of the perimeter columns. On my math, the actual WTC columns could probably stand (alone) about 300-400 feet before needing lateral bracing. (I'm not deeply committed to any particular height but the textbook example with a 1/10" steel tube can reach over 200 feet.) They got their lateral bracing at each floor (every 12' or so) from the spandrel plates and, ultimately, the corner connections to the perpendicular facade.
It's interesting to think about how it would work if it was just a windowless 3" steel facade. How tall could such a box go (especially if the plate thins as we go up)?
Like I say, these are math questions. When I've learned how to do the math, I'll feel more comfortable drawing any conclusions from it.
I like this too. But keep the core columns in mind. The "hole" is a square donut.
All good stuff to think about. But, like I say, until I work out the math problem, I'm tending to agree with the people who find all this too speculative.
To grant your main point, however: You might be right that, once the pipe-in-pipe model is adjusted to realistically match the properties of the WTC towers, it would collapse just the same by ROOSD. That's what I'm trying to prove with math.
Continuing with the OP: NIST measured significant inward bowing (on the order of a foot) in WTC1 floors 100 and 101, which were not impacted by the plane. Thus suggests that insulation damage from the impact was not absolutely necessary to cause substantial floor sagging.
https://www.metabunk.org/threads/ni...easurements-of-wtc1-bowing.12392/#post-269346
https://www.metabunk.org/threads/ni...easurements-of-wtc1-bowing.12392/#post-269346
Oystein
Senior Member
Thanks for fulfilling my prophecy that you would merely reword your bare incredulity.
Still no argument.
Yes, 364 pounds, much of which to cut colums that carry like 27 floors above them. Of course it would take far less to take out truss chords that bear a much smaller load.
You need to address why you think that rendering walls that depend upon lateral support laterally unsupported over 4 stories, making them 16 times as likely to buckle, would not buckle when trusses seriously pull them inwards.
Or why you think the tower above would not tilt and come down.
After all, reality on 9/11 showed this is what happened.
ETA: also, Henkka, I asked some more questions!
Why did you choose the Mina towers? Who told you of them?
You would restore a bit of trust in you if you could acknowledge that the 16000 pounds there were WILDLY out of character for what the bare minimum to take down a steel frame skyscraper.
You entirely FAILED to even just acknowledge the crucial fact that a taller building has far more potential energy to crush itself than a shorter building, reducing the amount of additional energy required to make it collapse.
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econ41
Senior Member
Yes. And so predictable.
Yes!
Begging the reality that is has nothing to do with the actual 9/11 collapses.
Oystein
Senior Member
True! This current diversion started as an answer to @Henkka 's question how much explosives it would take to simulate the actual collapses. My proposition assumes that what really happened was "fires heat trusses over some floors -> trusses sag -> sagging trusses tug wall inward -> wall buckles -> top tilts and comes down -> collapse". A way to make trusses sag and thus to start a collapse sequence similar to the above, all you have to do is cut enough bottom chords. I suggested on all trusses over 3 floors, which would make the walls 16 times more vulnerable to buckling and likely cave in. I estimate 75 pounds of well-placed high explosives could do that jobBegging the reality that is has nothing to do with the actual 9/11 collapses.
Henkka believed that far more explosives would be needed - without hinting what for.
Henkka has failed to address my claim that there are about 150 trusses spanning between one wall and the core over three floors
Henkka has failed to address the claim that 75 pounds might suffice to cut 150 bottom chords
Henkka has failed to address my assertion that cutting bottom cords makes trusses sag and pull in on the walls.
Henkka has failed to either acknowledge or doubt that removing lateral support over 4 floors makes the walls 16 times more vulnerable to buckling
Henkka has failed to address the assertion that one wall would buckle in the scenario I outlined.
Henkka has failed to say anything about the suggestion that failure of one wall woul make the top tilt and come down and result in runaway collapse.
My benevolent interpretation for all these failures, for Henkka's TOTAL FAILURE to address a single aspect of my argument, is that he is crassly out of his depth.
Henkka fails to see the gift I am giving him: a Truther theory for explosive demolition that could be squared with the extant evidence: you see, it takes so little to cut the chords. And no one really looked at the trusses much, for those got badly mangled and torn etc in the collapses. Would anyone actually report a severed truss chord? It could be done with steel-melting incendiaties even! Triggered by the heat of fires! It all makes sense! And no evidence for it - that's how clever the plan was, the perfect crime! 9/11 solved!
But no, Henkka insists on dozens, perhaps hundreds of tons of explosives.
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I think there has to be a misunderstanding somewhere here for you to say this… The whole point of the question was that if you wanted to make the building collapse in a way that resembled the actual 9/11 collapse, but do it with explosives instead of a plane,
1) How much explosives would you need?
2) Where would the explosives be placed?
econ41
Senior Member
It started referring to "actual collapses"
Hence my comment - because back in circa 2009 2010 that was the approach I took when, on two separate occasions, I offered to help a couple of serious truthers formulate pro-CD hypotheses.
I've been following the debate - but I miss the peak activity due to Time Zone issues. And four or five theme trails, all off-topic - is too much for me to attempt commenting on.
Welcome to the Club. You are not the only one whose efforts are being ignored.
Try counting the offers of explanation and help that I have extended to both @Henkka and @Thomas B .Hence my offers to help. Both you and I are competent teachers of these topics.
Definitely the work of genius.
And totally loses the plot which is to mimic the actual 9/11 collapses.
But don’t you see the difference… Between what is a sort of classical bottom-up implosion of a tower, and what you’re proposing? Nobody, in the history of planet earth, has ever looked at a tall steel building and thought to themselves: ”Hmm yes, we’ll demolish it by removing some floor supports near the top of the tower!” That’s not a thing. If you wanted to replicate what happened to the Landmark tower on the WTC, I guess you would be cutting the core and perimeter columns near the base. Not sure how much explosives you would need, but I’m guessing way more than 75 or 364 pounds.
As for the Mina towers, I remembered them being one of the larger demolitions, and looked up how many explosives it took. But you’re right, I ought to have looked up more demolitions to see if the 13k pounds was representative of other demolitions.
econ41
Senior Member
Wanna bet???
EXACTLY - resemble the ACTUAL 9/11 collapse. Which actual collapses started with "Top Block" dropping THEN transitioned into ROOSD. IF you trigger it with ROOSD - and I think it is technically feasible - THEN No Top Block dropping to START the collapse. So it doesn't achieve the goal of "in a way that resembled the actual".
Yes. And I've offered to discuss THAT hypothesis in another thread because it is way off-topic here.
I think these are good questions. They address the OP by asking us to specify exactly what damage to the structure a fire would have had to do in order to bring about a 9/11-style collapse. It allows us to quantify the energy that a fire would have had to deliver by other means.
If it would take an unrealistic amount explosives (compared, say, to the volume of the floors that need to be rigged), or if they would need to be placed outside of the floors that were on fire on 9/11, then that would suggest the answer to the OP question is no.
Oystein
Senior Member
What catastrophically confused thinking.
It takes 364 pounds to do a --> CONTROLLED!!!!! <-- demolition.
Of course significantly LESS would suffice if control was not needed.
Of course no one ever considered my method for a --> CONTROLLED!!!!! <-- demolition. Can you figure out why?
The challenge you gave us was nit - I repeat: NOT! - to simulate the --> CONTROLLED!!!!! <-- demolition of the Landmark Tower but in a different fashion. The challenge was to simulate the HIGHLY UNCONTROLLED fire-induced collapse initiation o ofcthe HIGHLY UNCONTROLLED twin tower collapses.
You STILL are in 100% FAILURE to address a single link of my complete, chain-linked argument!
How much longer are you going to dance around, unthinkingly, with your bare naked incredulity, pretending there is no argument for you to address!?
Oystein
Senior Member
This is nonsene on too many levels than I have time to unravel at this time. For starters: you obviously have no concept of how many orders of magnitude more energy fires brought to the action than even the biggest explosive CD ever. You fail entirely to appreciate that fire can damage a structure in several way that explosives can't. And these unrealistic amounts of explosives are of course a problem for TRUTHERS ONLY!
I’m not proposing to trigger it with ROOSD… I’m not proposing anything. I’m asking you guys about what you believe happened. I’m asking you to set explosives in the building to cause the same amount of damage as you believe the plane impact and fires caused on 9/11. If it’s the same amount of damage, and that damage caused the building to collapse on 9/11, then you should get a similar collapse. Whether it’s ”top block first” or ”ROOSD first” doesn’t matter to me.
It would be great (and entirely on topic) if you could quantify this for us.
I assume we agree that most of the energy of the fire was "wasted", i.e., not "delivered" to the structural components that needed to fail.
Since the energy of the fire was not focused on the task of bringing down the building, it becomes a good question whether the total energy of the fire minus the wastage from its inefficient application to the collapse mechanism bring the "orders of magnitude" into closer agreement.
econ41
Senior Member
Either those are three blatant lies or you don't understand what you are posting.
Blatant stupidity. "You should get a similar collapse even if it is totally different".
econ41
Senior Member
Your premise is arse about >> false:
Because the collapse initiation was triggered at a location where the fires focused sufficient heat. As I said - your thinking on that issue is backwards.
Oystein
Senior Member
You can with great ease do this yourself. Or can you not? I showed you how 75 pounds of explosives suffice. The typical combustibles in an office (paper, plastic, wood) have something like 4 times the energy release of high explosives. So. 75 pounds of explosives equivalent to 20 pounds of wood or paper. I'll leave to you how much conbustibles there are on 5 floors of the WTC and divide.
And then address the other points.
And my 75 pounds proposal.
And the simple observation that fires do in fact warp to pretzels steel structures all the time.
And then subtract the amount of times you've called us dishonest and stupid.
econ41
Senior Member
That will be an easy bit of arithmetic. Why do you sink into personal attack in the face of a statement of simple fact?
Sorry, I hadn't been following your debate with @Henkka in detail (I just liked those questions). I had to search to find it, but, yes, this is good:
This is where a load path diagram would really useful. Those chords seem awfully critical. More critical than I would have thought any engineer would have made them. But I guess it's possible. It's not obvious to me, anyway.
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