WTC Collapse Simulation using Unity/Besiege

Jeffrey Orling

Senior Member
I want to point out that as we can't see inside the towers we cannot know what happened to the steel frame, where is happened and the sequence that took place. At some point the capacity was below service loads and the top no longer had support. I would argue that there is no unique sequence. In act the two towers collapsed.. tops lost support but from a different plane strike at a different location... more or less the same result. So it seems there were multiple ways the tops could collapse.

How do you decide which of many sequences/scenarios is the right one?

Does it matter? If so why?
 

Jeffrey Orling

Senior Member
So what was holding the top up? Surely not only the facade columns. Is there any evidence that all the facade columns failed leading up to collapse of the top? Or did the facade columns collapse because the core columns lost capacity and the facade columns could now support the top without "help" from the core columns?
 

econ41

Senior Member
For the record @Jeffrey Orling I suggest that we acknowledge that these are aspects where you and I have a long history of disagreement over how much detail we need to reach supportable reasoned explanations.
I want to point out that as we can't see inside the towers we cannot know what happened to the steel frame, where is happened and the sequence that took place.
I contend that we can, for the Twin Towers, see and know enough to define what happened with a high level of certainty. And sufficient certainty to support the level of debate needed in this current thread. For example, we can be certain from the visual evidence that the "initiation stage" of both WTC Twin Towers was dominated by a cascading failure of columns losing their ability to carry vertical loads. And that much is sufficient to support current discussions. Yes, it is true we do not know, will never know, the exact sequence of column failures. But we don't need to know to progress reasoned explanation. Note that assertion does not apply to programming software simulation where I suggest the sequence has to be defined. (Somehow?) Which is one example of why reasoned engineering analysis can progress further than a computer simulation.

I would argue that there is no unique sequence. In act the two towers collapsed.. tops lost support but from a different plane strike at a different location... more or less the same result. So it seems there were multiple ways the tops could collapse.
So what? for each of those three assertions? What is the consequence? And there is ONE unique sequence for each tower. The one which actually happened. PLUS maybe dozens that did not happen. But nothing material to argument flows from that reality. There may have potentially been "...multiple ways the tops could collapse..." BUT only one of them actually happened. (One for each tower.) And again - so what?

How do you decide which of many sequences/scenarios is the right one?

Does it matter? If so why?
Respectively:
1) Why do you need to decide? Why not analyse what did happen? And ignore what didn't happen?
2) No!
3) Moot.
 
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econ41

Senior Member
Their conclusion is that they can't conclusively determine the damage that the aircraft did to the core, but it doesn't matter because the fires ultimately brought the building down.
That is the sort of conclusion that matches my biases. I'm experienced as a civil operations engineer and as a military engineer. Both bias towards real-time decision making and the need for rapid identification of the relevant critical path of decision making. From my perspective, there is rarely any benefit in spending effort on aspects of a problem that do not affect the outcome.
So any simulation that depicts collapse initiation properly must be able to model fires (heat, spread, duration), its effect on structural steel (with more or less insulation), and a model of how the loads in the steel structure shift as the steel softens.
I doubt it is possible to make such a simulation within the parameters so far defined in this discussion topic.

As a next step I suggest we need to define what form of "simulation" we are discussing AND what we mean by "depicts collapse initiation properly..." The primary distinction is between (1) a computer simulation which "looks like" the real event sufficient to help the "interested person" understand OR (2) a computer simulation that rigorously models the engineering applied physics of the actual mechanism. (In both instances limited to the "initiation stage")

Then "depicts properly" depends on which type of sym we intend AND the level of sophistication of the target audience. For a "looks like" model it could be sufficient to show a number of buckling columns resulting in tilting of the "Top Block" until a "Top Block starts to drop" point is reached - which is the end of the "initiation stage as I would define it. For reasons I can elaborate I doubt that it is possible to produce a rigorous simulation of the engineering applied physics.

No game engine does that, and Kostack doesn't either.
Because they are not engineering simulations. They are - in my terminology - "look like" simulations.

And, anticipating a "yes but!", no matter how sophisticated the "physics engine" in the software it still requires the programmer to define (therefore pre-requisite - understand) the physics.
 
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Jeffrey Orling

Senior Member
For the record @Jeffrey Orling I suggest that we acknowledge that these are aspects where you and I have a long history of disagreement over how much detail we need to reach supportable reasoned explanations.

I contend that we can, for the Twin Towers, see and know enough to define what happened with a high level of certainty. And sufficient certainty to support the level of debate needed in this current thread. For example, we can be certain from the visual evidence that the "initiation stage" of both WTC Twin Towers was dominated by a cascading failure of columns losing their ability to carry vertical loads. And that much is sufficient to support current discussions. Yes, it is true we do not know, will never know, the exact sequence of column failures. But we don't need to know to progress reasoned explanation. Note that assertion does not apply to programming software simulation where I suggest the sequence has to be defined. (Somehow?) Which is one example of why reasoned engineering analysis can progress further than a computer simulation.


So what? for each of those three assertions? What is the consequence? And there is ONE unique sequence for each tower. The one which actually happened. PLUS maybe dozens that did not happen. But nothing material to argument flows from that reality. There may have potentially been "...multiple ways the tops could collapse..." BUT only one of them actually happened. (One for each tower.) And again - so what?


Respectively:
1) Why do you need to decide? Why not analyse what did happen? And ignore what didn't happen?
2) No!
3) Moot.
I completely agree. My post was about how to model a computer simulation which looks like the real world collapse. So it may not matter the sequence, but it does mean that there was sufficient loss of capacity for the tops to descend. A sim would need to "select" a sequence or generate a sequence... leading the the result. I suppose you could simply select X number of columns and "remove them" and see what results. If it looks like real world you have a solution.
 
How do you know it's in accordance with real physics?
SmartSelect_20211110-150126_Samsung Internet.jpg
The video has been up for 2 years, no reason to assume it'll disappear; but I understand you enjoy a heightened feeling of drama?
I don't know whether the Detonate simulation is in accordance with real physics (it probably isn't considering that when building elements in Detonate are stressed they simply break apart instead of deforming, although the Detonate game is said to have realistic spreading of fire in real time http://www.wildebeestgames.com/detonate.html; the game is fairly old, hasn't been updated in many years, and there is no manual detailing how the fire spread is modeled, so I can't confirm whether these claims from the game maker are true).
With the in-built editor, create your own buildings using the library of hundreds of varied parts. Choose from brick, concrete, timber or steel materials, arrange them to your requirements.

With realistic spreading real time fire and a variety of projectiles such as flame thrower, exploding bullets and water hose.

When I said "in accordance with real physics" I meant (when addressing the OP) how would one be sure if the modeled collapse of a WTC-like building (hollow tube structure with rigid exterior columns, light-weight floor trusses, rectangular interior column region and open space floor design) using simulations from a sandbox game like Besiege was in accordance with real physics if other collision scenarios (such as the physics of a plane collision with a WTC-like building) could not be accurately simulated in simulations from that sandbox game, as was said to be the case in a previous thread https://www.metabunk.org/threads/ho...ngs-penetrate-the-wtc.3326/page-5#post-259628?



I linked the video because the simulation in that video (including with plane damage, fire and collapse) was similar to the scenario OP was trying to model (that being the collapse of the south tower following plane impact damage and fire).

I don't enjoy a heightened feeling of drama, but many videos I have seen that are hard to find (such as the one I linked) end up being made private or taken down, so I was saying that in order for people to have a copy of it for their records, it would be a good idea to download the video.
 
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econ41

Senior Member
I completely agree. My post was about how to model a computer simulation which looks like the real world collapse. So it may not matter the sequence, but it does mean that there was sufficient loss of capacity for the tops to descend. A sim would need to "select" a sequence or generate a sequence... leading the the result. I suppose you could simply select X number of columns and "remove them" and see what results. If it looks like real world you have a solution.
You identify two key points - and the discussion is not progressing either of them. They are:
(1) "..a computer simulation which looks like the real world collapse". Where the unresolved questions include "how much "look like"; how realistic do you want the underlying physics to be and whose perception do you want to satisfy? AND

(2) "A sim would need to "select" a sequence or generate a sequence." This means that the software works out the physics mechanism for us. I don't accept that as plausible. To specify how a graphics engine can simulate physics the programmer has to tell it what is needed. And It is not practical in the amateur home setting scenario to better the level of work that NIST can perform at the rigorous simulation of engineering physics. Even NIST has not attempted full sim modelling of Twin Towers collapses.
 

Mendel

Senior Member.
You identify two key points - and the discussion is not progressing either of them. They are:
(1) "..a computer simulation which looks like the real world collapse". Where the unresolved questions include "how much "look like"; how realistic do you want the underlying physics to be and whose perception do you want to satisfy? AND

(2) "A sim would need to "select" a sequence or generate a sequence." This means that the software works out the physics mechanism for us. I don't accept that as plausible. To specify how a graphics engine can simulate physics the programmer has to tell it what is needed. And It is not practical in the amateur home setting scenario to better the level of work that NIST can perform at the rigorous simulation of engineering physics. Even NIST has not attempted full sim modelling of Twin Towers collapses.
Well, machine learning can do that, in a way. You can say, I want a collapse that looks like the news footage of the event, and then you can have an algorithm tweak model parameters until that constraint is satisfied.

The question is, what are you going to learn from this that we didn't already know? We know (e.g. from Purdue's work) that there's more than one sequence that will satisfy the constraint. So we won't find "the" physics mechanism, we'll find one possibility, or maybe several possibilities, but not all of them. And we already know one!

So all you're really going to get is a 3D model animation collapsing in a way that's superficially similar to the actual WTC collapse. And you're getting that similarity because that's what you constrained the outcome to be like. You're not getting anything out of the model you haven't put in, except a repeat confirmation that impact&fires&physics suffice to explain the collapse.
 

econ41

Senior Member
Please excuse the reversed order of responding...
So all you're really going to get is a 3D model animation collapsing in a way that's superficially similar to the actual WTC collapse. And you're getting that similarity because that's what you constrained the outcome to be like. You're not getting anything out of the model you haven't put in, except a repeat confirmation that impact&fires&physics suffice to explain the collapse.
Exactly. Hence my so-far unsuccessful focus on persuading the OP @dylbie to define what his objective is. And I doubt he will get: "...a repeat confirmation that impact&fires&physics suffice to explain the collapse" UNLESS he decides to simulate what actually happened.

And "we" (collectively) already know what happened. Possibly @dylbie is not as fully aware. BUT any valid simulation must reflect what actually happened. And no way can "magic software" analyse the data and work out what happened without regard for what is already known.
Well, machine learning can do that, in a way. You can say, I want a collapse that looks like the news footage of the event, and then you can have an algorithm tweak model parameters until that constraint is satisfied.
Yes - possible to some extent. But that produces a "look like" model or simulation. With no guarantee that it will reflect the actual physics. No problem IF that is the goal. Hence - again - my suggestions that the OP define his goal. And, by the way, that is very much what Hulsey did - produced a "look like" faked simulation to meet the expectations of his AE911 audience.
The question is, what are you going to learn from this that we didn't already know? We know (e.g. from Purdue's work) that there's more than one sequence that will satisfy the constraint. So we won't find "the" physics mechanism, we'll find one possibility, or maybe several possibilities, but not all of them. And we already know one!
Actually, I suggest there is an even more fundamental question. Who is expected to benefit? Who is expected to learn? Because I don't think it is "we". And it certainly isn't "me". ;)

THEN - yes - there are multiple possibilities BUT only one actually happened ( one for each tower). But the following questions include asking "How can simulation help those who "we" are trying to teach? Specifically "What can a simulation show that is not already visible in the video and graphic record?

And I'm not saying there is no benefit. Only that a simulation will only help a small demographic sector of those who cannot understand without such an aid to learning. So it is essential that the OP identify his target "audience" because that will, in turn, help to determine how much detail the sim needs and how accurate it needs to be.
 
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dylbie

New Member
Can I just clarify I don't really have a goal. So your continued questioning on that topic is invalid.

I created a 'makeshift' 3D model in a game that cost $15 that runs fairly well on my consumer spec PC, and with that in mind, it gave me reasonable results, albeit with the sizeable limitations that I've stated in the original post.

This then made me question... Why if I can do this in my spare time with consumer grade products, why hasn't someone done more simulations with a super computer and professional/commercial architectural/structural software?

The only person I know is Kostack. Doesn't that seem odd based on the size of the debunker/truther movement? Isn't it odd that the AE9/11 group haven't commissioned a modern simulation to try and prove their theories?

You seem fairly confident that you know all the answers. By the way I'm sure there are people on the truther side who are as confident as you but with completely opposing views.

There seems to be a general consensus here on what happened to both towers, which to me make sense (although I admit I've not managed to read through all of the 1000s of threads on it here yet!) It would be good validate those opinions with a credible simulation now that the technology has advanced, and also as Mendel has interestingly raised the point about AI learning which would speed up the process.

I've never said it would be 100% correct, but it would give a good approximation. And maybe would answer some of the questions that the truther movement has.

So in conclusion, I've contradicted my first paragraph. The goal is to create a (semi) credible simulation that could answer some of the questions of the truther movement and their ridiculous claims.

But this is straying way off topic of the original post. We need another thread on this titled "Do we need a new simulation now processing power and software has advanced?"
 
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dylbie

New Member
Back on topic...

I've run some more simulations with Besiege where the limitations of the software are much more apparent. You can really see how the lack of deformation of the blocks limits it compared to the real-life collapse events.

Still, it's interesting to watch. I'll render some more videos later and stick them on YouTube if I have time this weekend.
 

Mendel

Senior Member.
The goal is to create a (semi) credible simulation that could answer some of the questions of the truther
I've been trying to explain that a new simulation probably wouldn't help here.
If you'd like to pursue this, could you collect a set of questions that you feel a simulation of a possible approximate collapse scenario could answer?

You can simply say that you'd like to do something interesting with the game, and nobody could question that. It's the ulterior purpose that I'm sceptic about.
 

econ41

Senior Member
Can I just clarify I don't really have a goal. So your continued questioning on that topic is invalid.
It is obvious that there is no clear purpose in what you propose OTHER THAN the reality that you enjoy playing with computer software. There is nothing wrong with having such a hobby. But you post the topic here - on a debate forum - asking for comments and critique. The invalidity is in your posting. NOT in member legitimately trying to help you. If your interest is in computer modelling - go for it. But stop pretending that it is the number one method of converting truthers or of explaining WTC collapses. It isn't and many of the reasons have already been put to you.

So why don't you join in the legitimate debate? Of what you are really trying to achieve? Why not recognise that "explaining WTC collapses" is NOT your goal?
This then made me question... Why if I can do this in my spare time with consumer grade products, why hasn't someone done more simulations with a super computer and professional/commercial architectural/structural software?

The only person I know is Kostack. Doesn't that seem odd based on the size of the debunker/truther movement? Isn't it odd that the AE9/11 group haven't commissioned a modern simulation to try and prove their theories?
Because there are few persons who see such simulations or modelling as a means to "prove their theories". In fact, as I and others have clearly stated, such models cannot "prove theories". They can only mimic what the program designer already understands AND the persons who such simulations may help are a very small number. For most persons who are "interested in learning" other methods of explanation are superior. And there is only a small sector of persons whose learning processes need and would benefit from visual models of the type you are suggesting.
You seem fairly confident that you know all the answers. By the way I'm sure there are people on the truther side who are as confident as you but with completely opposing views.
Ignoring the snide aspect of personal comment. Many of us do understand. And I certainly understand both the Twin Towers collapses and the training/communication processes relevant to what you are claiming you want to do even tho you keep denying you have a goal. There are no opposing views from the truther side which any truther has ever explained with validly reasoned argument. None.

There seems to be a general consensus here on what happened to both towers, which to me make sense (although I admit I've not managed to read through all of the 1000s of threads on it here yet!) It would be good validate those opinions with a credible simulation now that the technology has advanced, and also as Mendel has interestingly raised the point about AI learning which would speed up the process.
Then stop playing it both ways by conflating two topics. viz your desire to play with computer software whilst trying to make it force fit as a training tool to explain WTC collapses. It is NOT a good tool for explaining WTC collapses. It cannot "prove" the physics for reasons posted several times. It may help a small sector of the demography of those who are interested. Those who need visual modelling but for the majority, there is already sufficient visual material that already shows the main features of the collapses.
I've never said it would be 100% correct, but it would give a good approximation.
And, as I have said from the start, what do you mean by "good approximation"? How good? For whom does it have to be "Good enough"? OR more generally - who is your target audience? Do you actually believe there are still truthers active who have even a slight interest in learning the no CD truth about WTC collapses? And, if the implied goal is to help some truthers who want to learn, do you expect an amateur level video to influence them?
So in conclusion, I've contradicted my first paragraph. The goal is to create a (semi) credible simulation that could answer some of the questions of the truther movement and their ridiculous claims.
Correct. You have contradicted your first paragraph claim. You also contradict your 5th paragraph where you praised truther understanding which you now describe as "ridiculous claims". And by the way - telling them their claims are ridiculous probably wont help you persuade them.
But this is straying way off topic of the original post. We need another thread on this titled "Do we need a new simulation now processing power and software has advanced?"
I doubt there is a need for a new thread for two main reasons. #1 - The answer is no. There is not sufficient need for such a simulation at this late stage of discussion of 9/11 WTC collapses and #2 This forum is probably not the place for the discussion because the reasons are not technical. They mostly fall in the domain of HRM viz learning psychology and training.

And a final comment. Your opening claim was that our continued questioning on that topic is invalid. That is false. You posted the topic for discussion. There can be no legitimate discussion of how useful or effective your proposals are UNLESS we know what you are trying to achieve. You can probably enjoy, have fun using the software. It is not the best way of explaining WTC collapses but may assist a small demographic sector of interested persons. I doubt it is worth the effort for that small sector of interest at this late stage in 9/11 WTC collapse discussion.
 

Jeffrey Orling

Senior Member
Interested people have participated in discussions online about the WTC collapses. Some excellent analysis has come out of these discussions. The reason for the need for all of this is because people can't see inside the towers and know what was going on in any detail. Detailed analyses have been done about the visuals of the exterior including the debris pile.
There are some key take aways:
The failure was a progression of failures. This was because the continued presence of heat from unfought fires... which spread through the buildings... the redistribution of loads when a structural member failed.... the displacement of parts of the frame when heated steel expanded and caused lateral movements. It's not possible to know how and where the progression of failures was. In the case of 7WTC we have a clue because the collapse of the EPH telegraphed an axial failure(s) below it. 1WTC should inward distortion of the south face near the east side.
For the twin towers NIST proposed a facade column failure caused by heat expanded and sagging trusses. This makes sense when there was extensive truss involvement around the core and most of the perimeter. The facade supported about 50% of the upper block loads and so it's failure would lead to the top block dropping.
However the fires were raging in the core and weakening the structure inside the core. There was core column damage and destruction from the plane strikes... So it's possible that the core was losing capacity as well and it supported about 50% of the weight of the top block. It should be clarified that only 24 of the core's 47 columns supported the outside the core floor loads and trusses. Plane strikes did destroy a number of the perimeter core columns. Further... the outside the core slabs and trusses were supported by a belt girder encircling the core's 24 perimeter columns. The girder was supported by short cantilevered beam stubs. We simply cannot know how the core's steel was "behaving" because we couldn't see it. But a core failure would also lead to the tops descending. Failure was also likely progressing in the core region. Modeling the progression is complex and demands input of heat which was driving the destruction.
I suppose one could eliminate one column... loads would redistribute and then eliminate another or two... likely proximate the first one that failed and so on... until the capacity was below service load and the progression would go "run away" and the top would drop.
Go for it. See what it looks like. If you get it to look like real world... you might have figured something out.
 

dylbie

New Member
Thanks @Mendel and @Jeffrey Orling for your constructive comments. Your points are interesting and certainly something I'll think about whilst waiting to see the new Kostack simulations. It will be interesting to see he finds anything new. Or even if Blender/BCB can actually handle simulating something with so many objects and variables.
 

Jeffrey Orling

Senior Member
I don't need a simulation to see the towers from the exterior collapsing... That you can see in the real world vids.
Sims like Purdue are interesting to me and I would like to see some similar showing various sequences of the failure progressions in the towers leading to what looks like the collapses we saw. As I wrote I think there are likely many ways to get to the same result. And we might never know which way it was.
 

econ41

Senior Member
I don't need a simulation to see the towers from the exterior collapsing... That you can see in the real world vids.
Exactly. The video clips certainly show the main stages of collapse - the gross features - with more than sufficient accuracy.
Sims like Purdue are interesting to me and I would like to see some similar showing various sequences of the failure progressions in the towers leading to what looks like the collapses we saw.
I also find them interesting. Because - knowing how the collapses actually progressed - I can assess how accurate the simulation is. BUT that reality denies the claim that such sims are a primary teaching tool. For a person who already understands the collapse, they are no more than confirmation. if that.

As I wrote I think there are likely many ways to get to the same result. And we might never know which way it was.
For those of us who for some reason cannot accept that "we" already "know which way it was" a sim has some value., So. possibly you are one of those that a sim could help. Which does NOT override the issue that both @Mendel and I - possibly some others - have identified. Somebody has to already know what happened before a games modelling engine can be set up to demonstrate it. It won't do the physics from zero-base of its own accord.
 
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econ41

Senior Member
Thanks @Mendel and @Jeffrey Orling for your constructive comments. Your points are interesting and certainly something I'll think about whilst waiting to see the new Kostack simulations. It will be interesting to see he finds anything new. Or even if Blender/BCB can actually handle simulating something with so many objects and variables.
Should I assume that you @dylbie disagree with my even more focused suggestions? :confused: ;)

And don't want to discuss them? ;) No problem.
 
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Jeffrey Orling

Senior Member
For those of us who for some reason cannot accept that "we" already "know which way it was" a sim has some value., So. possibly you are one of those that a sim cold help. Which does NOT override the issue that both @Mendel and I - possibly some others - have identified. Somebody has to already know what happened before a games modelling engine can be set up to demonstrate it. It won't do the physics from zero-base of its own accord.
Econ...
I have long held the belief that the collapse was core driven... ultimately there was insufficient axial strength to support the tops. I don't anyone knows the "last columns standing" before release.... which includes knowing the columns that failed leading up to the release.
 

econ41

Senior Member
Econ...
I have long held the belief that the collapse was core driven... ultimately there was insufficient axial strength to support the tops. I don't anyone knows the "last columns standing" before release.... which includes knowing the columns that failed leading up to the release.
I'm familiar with your positions on many aspects of WTC collapse @Jeffrey Orling. I'm not persuaded by "core driven" or the related issue of the emphasis you place on core columns and perimeter columns somehow acting as separate groups. Note I said "not persuaded". I'm agnostic on the issue. It does not arise in my explanations and I've never seen convincing valid proof.

What I assert should be undeniable is that the main process driving the Twin Towers initiation stage was a cascading failure of columns losing the capacity to carry vertical loads. That much is the dominant feature clearly seen in the video record.

Therefore it must be a mainstream feature of any valid simulation proposed by @dylbie. Independent of who he sees as his target audience. Whether hard-line truthers or sophisticated professional engineers or any others between those extremes. And therefore MUST** be shown by any valid simulation - so the following comments are "on-topic".

One other area where you and I have differed for many years is the issue of a specific sequence of column failures. We agree that we can never know which column was first, second, third etc... You say "I don't [think] anyone knows the "last columns standing" before release.... which includes knowing the columns that failed leading up to the release." That is true but it does NOT mean you cannot reason further. That reality is not a barrier to continuing valid reasoning.

You disagree with my arguments which say how the failure of the first column led to load redistribution of load which then failed the second column, followed by the third, fourth etc >> I maintain the argument is valid even though we don't know which columns were first, second etc. Many engineers are "left-brained" - driven by needs for specificity - and draw the same line at that point as you do. "If we cannot know which column was first, second, etc we cannot think further". I don't accept that limitation. As "we" - you and I - have discussed many times of the years. More important I've never had anyone prepared to attempt to prove my argument wrong. Because it isn't. "They" simply cannot process it.

This diagram can be used to help validly explain the actual mechanism of Twin Towers initiation stage. Even though it is neither a replica nor as complex as the real WTC tower structure.
7colsA2-400-withfirenotated.jpg or this one makes it even simpler >> 7colsA2-400-withcutsnotated.jpg

And - by the way - this discussion is fully "on-topic" BECAUSE any valid simulation of WTC Twin Towers collapse MUST** as a minimum demonstrate the key feature of each of the two main stages. And the sequenced cascading failure of columns in vertical axial loading is the key feature of the "initiation stage".


** And I'm available for counterargument rebuttal if anyone wants to disagree with "MUST". ;)
 
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Jeffrey Orling

Senior Member
You disagree with my arguments which say how the failure of the first column led to load redistribution of load which then failed the second column, followed by the third, fourth etc >> I maintain the argument is valid even though we don't know which columns were first, second etc. Many engineers are "left-brained" - driven by needs for specificity - and draw the same line at that point as you do. "If we cannot know which column was first, second, etc we cannot think further". I don't accept that limitation. As "we" - you and I - have discussed many times of the years. More important I've never had anyone prepared to attempt to prove my argument wrong. Because it isn't. "They" simply cannot process it.

This diagram can be used to help validly explain the actual mechanism of Twin Towers initiation stage. Even though it is neither a replica nor as complex as the real WTC tower structure.
7colsA2-400-withfirenotated.jpg or this one makes it even simpler >> 7colsA2-400-withcutsnotated.jpg

And - by the way - this discussion is fully "on-topic" BECAUSE any valid simulation of WTC Twin Towers collapse MUST** as a minimum demonstrate the key feature of each of the two main stages. And the sequenced cascading failure of columns in vertical axial loading is the key feature of the "initiation stage".


** And I'm available for counterargument rebuttal if anyone wants to disagree with "MUST". ;)
No I don't disagree.. failed column "hands off its" load to the closet columns... so the failure radiates. It's almost always more than 1 column which receives additional loading when none column fails.
 

dylbie

New Member
@econ41 I apologise if you've discussed at length the following points which I'm about to ask here - as I say I haven't read every post on this site...

But I'd be interested to hear your calculations for three collapse scenarios - firstly on how many core columns can be removed before the structure starts to fail. Secondly, I'm also interested to know if you've done any independent calculations on how many exterior columns would need to fail for the whole structure to buckle and give way. Thirdly, if you have calculated failure columns on WTC2 which gave that 20 degree tilt to the East, and on WTC1 which gave the tilt to the South.

Do you think it was the exterior columns failed first, or do you think there's any possibility that the core could have failed first due to fire which then caused the exterior columns to buckle? Or do you think everything became overloaded all at once and the core and exterior columns failed at exactly the same time?
 
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Jeffrey Orling

Senior Member
I made the following sketch for what the core failure sequence might be.

Core Failure Cartoon_page1.jpg

I think... guess... that more of the core would have to fail for a collapse to be triggered.
At one time years ago I offered a "scenario" where the core was structurally hollowed out at the plane crash region and the hat truss carried / transferred the failed column loads. Columns and floors above the hollowed out crash zone would be "hanging" from the truss and their loads would be transferred to the continuous remaining columns of the core and the perimeter... as more and more core columns failed eventually there was not enough axial support and the top collapsed.
I believe that core column buckling might have been enabled by the over heated beams expanding and displacing columns leading to them buckling.
Just a guess
 

econ41

Senior Member
@econ41 I apologise if you've discussed at length the following points which I'm about to ask here - as I say I haven't read every post on this site...
The Twin Towers collapses were complex events and there is a lot to absorb and understand. I find the most practical way to analyse is to start from the big picture and work down into detail if that is needed.

For example, the collapses for both Twin Towers were by near enough the same mechanisms. And both occurred in two main, distinct stages. The "initiation stage" allowed the Top Block to start falling. Then the "progression stage" followed with rapid "global" collapse down to ground level. Do you agree that those are the two main stages? If so - we have a starting point for further discussion. (And - as the discussion progresses - I will need to identify two additional "sub-stages" but rain check those for now.)

Now if you agree with those two main stages the next issue is to identify the mechanisms of that stage. And each of those two stages was dominated by one main process.

For the "initiation stage" the dominating process was the cascading sequenced failure of columns as they lost the capacity to withstand vertical loads. << And that is the main theme I have been addressing in recent posts. And the topic will refer to later in this post.

For the "progression stage" the main feature of the mechanism was that falling debris impacted on office space floors and missed the columns. The process is descriptively (and controversially) labelled by the acronym "ROOSD" meaning "Runaway Open Office Space Destruction". Take a rain check on that process at this stage.

Then I have suggested that, for any simulation to be valid, it must show a sufficient replication of those four main features of Twin Towers collapses. Viz two stages each with its own distinctive mechanism. Another point for agreement or further discussion.

Now with that long scene setting introduction let me respond to your third paragraph questions:
Do you think it was the exterior columns failed first, # or do you think there's any possibility that the core could have failed first## due to fire which then caused the exterior columns to buckle?### Or do you think everything became overloaded all at once and the core and exterior columns failed at exactly the same time?####
Answers in brief:
# No!
## No!
### Fire was observed to indirectly cause perimeter column buckling.
#### Definitely not! It both "was" and "had to be" a sequenced "cascading" failure.

EXPLANATIONS
What did happen was a cascading sequenced failure of columns. Similar to toppling a row of dominoes. (But a couple of grades more complicated - fuller explanation later if needed.) Setting aside the columns cut by the initial impact of the aircraft all the remaining columns failed because they became too weak to carry the imposed vertical loads. i.e. the imposed weight of the Top Block pulled down by gravity. And the "big picture" video record shows that the top block started to tilt slowly - over many minutes but progressively getting faster. Since it took minutes the column failures couldn't be simultaneous.

So that "big picture" proves some key facts:
(a) the columns did NOT all fail simultaneously;
(b) it took some time therefore aspects of the failure were sequenced. (Again - a point for a fuller explanation - later - if needed.);
(c) Because the top Block remained structurally intact it means that all failing columns were moving at the same time tho at different rates; (again - yes a point for discussion etc...)
(d) THEREFORE perimeter was failing in the same period of time that core was failing. NEITHER core nor perimeter "failed first"; AND
(e) point ### > Some perimeter columns were INDIRECTLY triggered to fail by heat. The heat weekend floor joist trusses sagged. Sagging trusses started to cause perimeter columns to bow inwards. Once started that IB process would become self-sustaining. (Another point for more explanation if needed...)

That should be enough to give an overview summary.

Then I suggest a rain check on your specific questions about calculations - your second paragraph.
But I'd be interested to hear your calculations for three collapse scenarios - firstly on how many core columns can be removed before the structure starts to fail. Secondly, I'm also interested to know if you've done any independent calculations on how many exterior columns would need to fail for the whole structure to buckle and give way. Thirdly, if you have calculated failure columns on WTC2 which gave that 20 degree tilt to the East, and on WTC1 which gave the tilt to the South.
 
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Thanks @Mendel and @Jeffrey Orling for your constructive comments. Your points are interesting and certainly something I'll think about whilst waiting to see the new Kostack simulations. It will be interesting to see he finds anything new. Or even if Blender/BCB can actually handle simulating something with so many objects and variables.
Everything I have seen so far suggests that a physical model of the towers collapse would provide a much better realistic model of the collapse sequence than most rigid body simulations in physics sandbox games would give. One thing that would be important when constructing such a physical model would be keeping in accordance with scaling laws and not designing a physical model that has parts that are too strong for that smaller scale. The physical model would have to be at a smaller-scale because a full-size model of the WTC towers is obviously infeasible for the average person to finance and construct on their own.

A thread about one type of physical model of the towers is here:
https://www.metabunk.org/threads/cr...-of-the-world-trade-center-twin-towers.11685/

This first thread thread (especially towards the end) focuses on the possibility of constructing physical models made with pasta representing the rigid outer perimeter columns and floors represented by wooden blocks. I think this is an interesting model to set up because of its relative ease in construction (needing mainly pasta, wooden blocks and weights), although the core columns in such a model might be more difficult to construct and make the physical model unrealistically sturdy.

Another thread about a different type of physical model of the towers is here:
https://www.metabunk.org/threads/to...llapse-of-the-wtc-towers-on-9-11.7396/page-11
The second thread focuses on other physical models, such as a free-standing wooden floor model with magnets, plastic, and screws being used to represent the seated connections connecting the wooden floors to the wooden exterior columns.


An added benefit of the first model imo is that compared to other models (such as a free-standing wooden model), provided that the correct method of inputting energy is applied (such as through steam and not through fire, the latter of which would likely burn the dry pasta to a crisp), the softening of the pasta in that physical model would better represent how steel softens and gradually loses its rigidity under higher temperatures than a free-standing wooden model would.
Once started that IB process would become self-sustaining. (Another point for more explanation if needed...)
IB stands for inwards buckling (of the exterior columns as a result of sagging floor trusses) in this context?
I made the following sketch for what the core failure sequence might be.

Core Failure Cartoon_page1.jpg

I think... guess... that more of the core would have to fail for a collapse to be triggered.
At one time years ago I offered a "scenario" where the core was structurally hollowed out at the plane crash region and the hat truss carried / transferred the failed column loads. Columns and floors above the hollowed out crash zone would be "hanging" from the truss and their loads would be transferred to the continuous remaining columns of the core and the perimeter... as more and more core columns failed eventually there was not enough axial support and the top collapsed.
I believe that core column buckling might have been enabled by the over heated beams expanding and displacing columns leading to them buckling.
Just a guess
OOS is the abbreviation for Open Office Space right?

I assume that the progression sequence for the south tower would be notably different for the south tower (which I believe OP was trying to model from their video), as the plane impact damage and fires were much more concentrated away from the core region and more focused on the south, east, and north sides of the building. Also, it appears from visual evidence that exterior column failure was much more pronounced just prior to collapse for the south tower than for the north tower. The south tower collapse visually appeared to start with buckling of exterior columns on the south and east sides of the south tower and then the top block leaning to the east and falling down, with a progressive collapse of the south tower then ensuing. The north tower collapse visually appeared to start with hat truss and interior column failure (and the antenna leaning and falling to the southeast), the top block coming down, and then the exterior columns at and just below the plane impact floor region buckling (aside from the exterior column buckling that was already taking place at the south face where the most active fires appeared to be raging at the time of collapse of the north tower), with a progressive collapse of the north tower then ensuing.
 

Jeffrey Orling

Senior Member
Regarding "failed columns"... certainly axial failure attended because the tops drop down. So let's talk about what those failures were/looked like.

I am thinking if you have a structure with 47 core columns and 120 facade columns... in the case of the twin towers... and 57 perimeter columns and 24 "interior/core" columns and the buildings collapse down... columns keeping them up failed.
TWIN TOWERS
In the case of the twins we know several columns were severed by the plane strikes and several were also "bent", dented and so forth.
So for the top blocks to drop... what was the columns failure(s)?

If there was a load redistribution... multiple columns were removed (by plane) and their loads were transfer laterally to other columns. As there was no immediate collapse... capacity was adequate. Likely no change or settling of the top. But the fire caused several things.... loss of capacity, elongation of heated steel. Both or either of these could lead to further erosion of capacity.... and or more columns "failing" and their load being transferred.

How does that actually look? If a column miss aligns and buckles from lack of bearing area for example... the intact column on to would presumably move down. But in so doing it would have to "drag" the frame down with it. Might not be much movement... but does a failed columns loose all capacity? It is not "disappearing".
How does this look?
If overheated beams push at a column and it yields it might be deforming. Column to column connections were unbraced. But perhaps it broke the end to end splices and the top slide past the bottom.... bearing was lost... Does the top drop? Is it buckled?

How can there be local "dropping" or buckling without the frame distorting? Can a distorted frame transfer loads efficiently or at all?

What does the "process" of column failure look like?

I raise the question because I don't observe and "downward" motion of the top until it "releases". There seems to be a contradiction or... the column failures were extremely rapid that it was hard to observe except at inadequate aggregate capacity and release.
 

Jeffrey Orling

Senior Member
Everything I have seen so far suggests that a physical model of the towers collapse would provide a much better realistic model of the collapse sequence than most rigid body simulations in physics sandbox games would give. One thing that would be important when constructing such a physical model would be keeping in accordance with scaling laws and not designing a physical model that has parts that are too strong for that smaller scale. The physical model would have to be at a smaller-scale because a full-size model of the WTC towers is obviously infeasible for the average person to finance and construct on their own.

A thread about one type of physical model of the towers is here:
https://www.metabunk.org/threads/cr...-of-the-world-trade-center-twin-towers.11685/

This first thread thread (especially towards the end) focuses on the possibility of constructing physical models made with pasta representing the rigid outer perimeter columns and floors represented by wooden blocks. I think this is an interesting model to set up because of its relative ease in construction (needing mainly pasta, wooden blocks and weights), although the core columns in such a model might be more difficult to construct and make the physical model unrealistically sturdy.

Another thread about a different type of physical model of the towers is here:
https://www.metabunk.org/threads/to...llapse-of-the-wtc-towers-on-9-11.7396/page-11
The second thread focuses on other physical models, such as a free-standing wooden floor model with magnets, plastic, and screws being used to represent the seated connections connecting the wooden floors to the wooden exterior columns.


An added benefit of the first model imo is that compared to other models (such as a free-standing wooden model), provided that the correct method of inputting energy is applied (such as through steam and not through fire, the latter of which would likely burn the dry pasta to a crisp), the softening of the pasta in that physical model would better represent how steel softens and gradually loses its rigidity under higher temperatures than a free-standing wooden model would.

IB stands for inwards buckling (of the exterior columns as a result of sagging floor trusses) in this context?

OOS is the abbreviation for Open Office Space right?

I assume that the progression sequence for the south tower would be notably different for the south tower (which I believe OP was trying to model from their video), as the plane impact damage and fires were much more concentrated away from the core region and more focused on the south, east, and north sides of the building. Also, it appears from visual evidence that exterior column failure was much more pronounced just prior to collapse for the south tower than for the north tower. The south tower collapse visually appeared to start with buckling of exterior columns on the south and east sides of the south tower and then the top block leaning to the east and falling down, with a progressive collapse of the south tower then ensuing. The north tower collapse visually appeared to start with hat truss and interior column failure (and the antenna leaning and falling to the southeast), the top block coming down, and then the exterior columns at and just below the plane impact floor region buckling (aside from the exterior column buckling that was already taking place at the south face where the most active fires appeared to be raging at the time of collapse of the north tower), with a progressive collapse of the north tower then ensuing.
Interesting comment. I suppose I could do a similar sketch for the failure progression of 2WTC. I would like to see reaction to my post above... relating to the SPEED of the failure or the columns. It may be that the column failure... going from having sufficient capacity for the service loads.... to having capacity drop below loads was an extremely rapid "runaway" progression. I am thinking of something like the failure of a steel truss bridge such as this:

Source: https://www.youtube.com/watch?v=RBnUpe4qp3o


There are other similar failures... Structure holds until it doesn't and it collapse in one fell swoop. Maybe this is how the top's behaved... once capacity was below required... they simply started moving and in the path of least resistance. For 2WTC is was tipping to the SE and falling down... for 1WTC it was basically slipping laterally and falling down.

The main point being... load redistribution was a rapid and runaway process.
 

econ41

Senior Member
Everything I have seen so far suggests that a physical model of the towers collapse would provide a much better realistic model of the collapse sequence than most rigid body simulations in physics sandbox games would give. One thing that would be important when constructing such a physical model would be keeping in accordance with scaling laws and not designing a physical model that has parts that are too strong for that smaller scale.
I doubt there is much difference in the practical aspects. The big and unresolved issue with physical models or simulations is in the presumption that they will benefit a large number of persons who would not be sufficiently helped by other methods of teaching/learning. The actual mechanism of the initiation stage of Twin Towers collapses cannot be accurately modeled or simulated in detail. So, whether sim or model, it would have to be a simplified demo of the main principle. And for most persons who are interested in learning the principle of cascading collapse can be sufficiently explained by discussion of something like this:
7colsA2-400-withfirenotated.jpg

... which could be the basis of a physical model as per one thread of the previous discussions you referenced.

IB stands for inwards buckling (of the exterior columns as a result of sagging floor trusses) in this context?
The observed "Inwards Bowing" of the perimeter which would start failure of columns. NIST identified it as the probable trigger for collapse. That is a reasonable suggestion because it does not rel;y on direct heat weakenting of coulmns to cause failure. Tho' direct heat weakening is another possibility - less likely in my opinion.

IB stands for inwards buckling (of the exterior columns as a result of sagging floor trusses) in this context?

OOS is the abbreviation for Open Office Space right?
Yes. Usually seen in the context of the descriptive acronym "ROOSD" >> "Runaway OOS Destruction"
I assume that the progression sequence for the south tower would be notably different for the south tower# (which I believe OP was trying to model from their video)##, as the plane impact damage and fires were much more concentrated away from the core region and more focused on the south, east, and north sides of the building.###
# Not so. The two progression stages involved essentially the same mechanism.
## As it stands the OP simulation does not even grossly represent either of the two main stages. And for the progression stage it does not simulate the two dominant visual aspects of the real event viz (1) ROOSD as the driving mechanism OR (2) Perimeter column "peel off" and separation into medium to large sheets of still connected but unbuckled columns.
### All that is "initiation stage" and had zero effect on "progression stage".

Also, it appears from visual evidence that exterior column failure was much more pronounced just prior to collapse for the south tower than for the north tower. The south tower collapse visually appeared to start with buckling of exterior columns on the south and east sides of the south tower and then the top block leaning to the east and falling down, with a progressive collapse of the south tower then ensuing. The north tower collapse visually appeared to start with hat truss and interior column failure (and the antenna leaning and falling to the southeast), the top block coming down, and then the exterior columns at and just below the plane impact floor region buckling (aside from the exterior column buckling that was already taking place at the south face where the most active fires appeared to be raging at the time of collapse of the north tower), with a progressive collapse of the north tower then ensuing.
Yes there were some superficial differences between the Towers. They had no significant effect on the underlying mechanisms which were near enough identical for the two twin towers.
 

Jeffrey Orling

Senior Member
Let's discuss the "initiation" stage in general for the twin towers.

The towers were both structurally damaged by the planes smashing through the buildings... severing several 3 story tall columns, "damaging" others (denting, distorting). As the buildings "survived" this "destruction"... there was obviously "capacity" to support loads above (what would become the top blocks). We understand this to be the case because structural design includes "reserve capacity". So if a column is supporting 100,000# it is likely designed to supported say 150,000#... the 50,000# being the reserve capacity.

If a column is severed its loads are redistributed to adjacent columns... presumably each one taking a portion of the failed column's loads. So if the reserved capacity is adequate, loss of a single column may not lead to further damage/destruction or collapse.

However if several columns are removed this may over load the adjacent columns... unless they too can "hand off" the loads to other adjacent columns and further from the initial failed column. Long story short... when columns are removed the "reserve capacity" is being used and the design might come close to having 0 reserve capacity. Think of a 1x19 multi-strand wire. If one strand "breaks" the remaining 18 will likely carry the load... but then two strands break and it comes closer to failing. It passes the point of no return and the wire parts in a virtual instantaneous failure.

In the towers post plane strike... heat was the "energy input" in the "equation". It was both weakening the steel... and causing steel to expand. What was likely expanding were the steel beams which braced columns and supported the floors inside the core. Heated trusses were pushing or pulling at the facade and the belt girder around the core (NIST theory).

Heat was "eroding" the performance of the structure.... It may have, in the core, led to one column failure after another... forcing remaining columns to carry more load and working at close to capacity including reserve capacity.

What may have happened... is that like with the multi-strand wire.... all capacity was used up and there was an almost instantaneous failure of all columns and the tops became unsupported and began to descend. Looks like in 2WTC the descent fell toward the SE where there was the most loss of columns (plane strike).... and in 1WTC the descent was more straight downward. In both cases there was some amount of lateral translation of the top mass... column ends were no longer axially aligned and offering resistance.

So my take away is that load redistribution "worked" until all reserve capacity was used up and then all remaining columns failed more or less at once. The hat trussed may have been effective in load redistribution to most of the columns. But in the end there were too few columns to support the load.
 

econ41

Senior Member
Let's discuss the "initiation" stage in general for the twin towers.
Your post is a good "lay-man's" summary of how "load redistribution" drove the cascading failure of columns. Which was the key feature of the "Initition Stage"

Hence my contention that any valid simulation must demonstrate at least a simplified version a cascading failure >> load re-distribution. The same assertion applies to physical modelling - in previous discussions I favoured using wax candles as columns because they allow mimicking of failure by heat weakening. Using a couple or three hair dryers to soften the wax candles. A true model of heat weakening failure of columns.

You also identify the two key issues that came out of the "initiation stage" and set up the scenario for progression. These two are:
What may have happened... is that like with the multi-strand wire.... all capacity was used up and there was an almost instantaneous failure of all [remaining] columns and the tops became unsupported and began to descend.
BTW did happen - not just "may have happened". ;) ..and you repeat the point for emphasis:
load redistribution "worked" until all reserve capacity was used up and then all remaining columns failed more or less at once.
THEN the most important point of all
column ends were no longer axially aligned and offering resistance.
This is why the "progression stage" fell at about 2/3rds "G". The columns were missed - bypassed - by the falling mass >> causing "ROOSD".

So let's look a bit further as to how that "reserve capacity" is used up. You say:
So if a column is supporting 100,000# it is likely designed to supported say 150,000#... the 50,000# being the reserve capacity.
I suggest that there may have been a lot more than 50%"reserve" but let's look at the principles using a simplified model. A single row of columns and we heat a couple til they fail:
7colsA2-400-withfirenotated.jpg or make it a bit simpler - let's start with some cut columns 7colsA2-400-withcutsnotated.jpg

Let's assume your figures @Jeffrey. Each column was originally loaded with 100,000. And we cut columns "A" and"B".

The 100,000 that each was carrying is still hanging off the end of the upper structure - the "Top Beam". (Call it the "Hat Truss" if it helps.)
Question #1. What column(s) now carry the 200,000 that was held by "A" and "B"??
Question #2: How much of the 200,000 re-distributes to column "C"
AND
Question #3: What happens to the load on "D" (Hint: does it increase or decrease?)

And understanding those factors for the "cut column" example should give a relative layperson enough insight into how load redistribution can easily overcome the "reserve capacity" of columns that have not yet failed.

The "failed by heating" example is a bit more complicated - we may not need to go there. You identified the problems @Jeffrey in a previous post:

Regarding "failed columns"... certainly axial failure attended because the tops drop down. So let's talk about what those failures were/looked like.
.....

If there was a load redistribution... multiple columns were removed (by plane) and their loads were transfer laterally to other columns. As there was no immediate collapse... capacity was adequate. Likely no change or settling of the top. But the fire caused several things.... loss of capacity, elongation of heated steel. Both or either of these could lead to further erosion of capacity.... and or more columns "failing" and their load being transferred.

How does that actually look? If a column miss aligns and buckles from lack of bearing area for example... the intact column on to would presumably move down. But in so doing it would have to "drag" the frame down with it. Might not be much movement... but does a failed columns loose all capacity? It is not "disappearing".
How does this look?
"How does it look?" >> as I said it is more complicated. Let's see if the simple case helps - the "cut columns version - we can discuss the heat-driven failures later if there is interest.
 
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econ41

Senior Member
Hi @Jeffrey Orling. I see that you "liked" my post. Why not take the bit of a challenge I posted - possibly set an example for other members to follow?

Can you suggest answers to the three questions?

Let's assume your figures @Jeffrey. Each column was originally loaded with 100,000. And we cut columns "A" and"B".

The 100,000 that each was carrying is still hanging off the end of the upper structure - the "Top Beam". (Call it the "Hat Truss" if it helps.)
Question #1. What column(s) now carry the 200,000 that was held by "A" and "B"??
Question #2: How much of the 200,000 re-distributes to column "C"
AND
Question #3: What happens to the load on "D" (Hint: does it increase or decrease?)

No need for numbers - general qualitative answers will suffice - words like "most", "more", "doubled" or "multiplied".

;)
 
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Jeffrey Orling

Senior Member
@Econ.... Only a guess.... I suspect the 200K # will be distributed by the hat truss...
Col C will pick up the most new load followed by D, then E and so on.

If failure is at 150k# C may be carrying just under 150K# and D, E, & F the same. The structure is close to failure and doesn't take much to push it to failure/collapse.
 

econ41

Senior Member
@dylbie Let's see if we can return to your OP and offer constructive comments.

You have indicated that part at least of your purpose in the simulation is to help others, including truthers to understand the Twin Towers collapses.

Do you agree that to be effective the simulation should mimic the key features of the actual collapse? That it should look like the real event?

If you agree that much, then I suggest that there are some gross visual aspects of the collapse that should be modelled:

1) The Top Block, as it started to drop, was still structurally intact. It didn't break up until after it started dropping. Your first draft sim shows break up starting with the Top Block before it fell. The initial break up was, in the real event, confined to the impact andfire damaged zones.

2) Both "Top Blocks" tilted, WTC2 far more than WTC1. Most truthers watching the sim would expect some reference to it. You could model in a tilt of about 10 degrees - a compromise between the two real tilts where WTC2 was about 22 degrees IIRC and WTC1 was less.

3) The "progression" stage saw various medium to very large "sheets" of perimeter columns peel off and topple away. Can the software incorporate some pre-determined mix of sheet sizes OR actually use randomising?

So - just two questions:
(a) Do you agree that the sim should closely resemble the visual features actually seen on 9/11?
AND
(b) What are your thoughts on the 2-3 examples I suggested?
 

econ41

Senior Member
@Econ.... Only a guess.... I suspect the 200K # will be distributed by the hat truss...
Col C will pick up the most new load followed by D, then E and so on.

If failure is at 150k# C may be carrying just under 150K# and D, E, & F the same. The structure is close to failure and doesn't take much to push it to failure/collapse.
OK. Let me explain the real answers without waiting to see if any other members are bold enough to take the challenge.

"Question #1. What column(s) now carry the 200,000 that was held by "A" and "B"??"
Answer: All the other columns will carry different loads. It depends partly on how stiff the "Top Beam" is BUT the left end of the Top Beam is now cantilevered out past "C". The 200,000 from that part is trying to pull the left end of the beam downwards. So it is pivoting over "C". And that means it is trying to lift off all the columns right of "C".

Question #2: How much of the 200,000 re-distributes to column "C"
Answer: "C" will carry much more than 200,000. Exactly how much more depends on the stiffness of Top Beam. (It would take specific details plus calculation to work out exactly. Preferably by FEA.) Remember there is still 100,000 "hanging" at "A" so it is a lever pivoting over the fulcrum of "C".

Let's simplify the layout for purposes of explanation. IF the Top Beam only went as far as "D" the force resulting on "C" from missing "A" would be an additional 300,000. Purely due to "leverage" Similarly, the force on "C" resulting from the removal of "B" would be 200,000. Net total on "C" 600,000 (300 plus 200 plus the original 100) And that overload is more than enough to dispose of a 5 times FoS "reserve capacity. BUT remember I've simplified the structure by shortening the Top Beam. Reality would not be so extreme.

AND
Question #3: What happens to the load on "D" (Hint: does it increase or decrease?)
Answer: The load on "D" will reduce dramatically - it will probably even go into tension. IF we stay with the shortened top beam ending at "D" and if my 80+yo brain doesn't make a silly error.. the load on "D" will "reduce" from the initial 100,000 to -200,000 i.e. tension or uplift on "D". THEN is we restore all of the Top Beam the effect on "D" will be far less dramatic but impossible to guess without a full FEA analysis of the statically indeterminate structure. The "flexibility" of the Top Beam AND the elasticity of the columns and all the lower structure comes into play. It gets very complicated.

So provided I haven't made any silly old-farts errors - those are the figures. And even if I've got one or two numbers wrong - the principle is correct. So, bottom line, load redistribution WAS the driving feature of Twin Towers collapse initiation stage. And it can easily overload columns whether they have 50% reserve capacity - your version @Jeffrey - to a full 5 times FoS - my version - which is probably more realistic.
 

Jeffrey Orling

Senior Member
@econ....
The columns at least in the core carried different loads. You can tell from their cross sectional area... which can be seen in my earlier sketch.
In real world the "structure above" failed columns I suspect was quite rigid and acted effectively to redistribute the loads to all columns... Your diagram is more like 2WTC than one because of the asymmetry. And then there was the exterior tube... which really acted like a tube and not rows of columns.
 

econ41

Senior Member
@econ....
The columns at least in the core carried different loads. You can tell from their cross sectional area... which can be seen in my earlier sketch.
In real world the "structure above" failed columns I suspect was quite rigid and acted effectively to redistribute the loads to all columns... Your diagram is more like 2WTC than one because of the asymmetry. And then there was the exterior tube... which really acted like a tube and not rows of columns.
My example correctly explains the relevant principles. And it should be easily understood by any member who wants to debate the physics of WTC collapses OR to simulate the collapses which depended on the same applied physics.

Breaking complex things down into separate building blocks is a sound, proven teaching technique. I'm aware that it may not suit some members. If other members also show no interest in comprehending the physics which is the foundation of the OP proposed simulation - I won't press the matter further.
 

dylbie

New Member
@dylbie

1) The Top Block, as it started to drop, was still structurally intact. It didn't break up until after it started dropping. Your first draft sim shows break up starting with the Top Block before it fell. The initial break up was, in the real event, confined to the impact andfire damaged zones.

2) Both "Top Blocks" tilted, WTC2 far more than WTC1. Most truthers watching the sim would expect some reference to it. You could model in a tilt of about 10 degrees - a compromise between the two real tilts where WTC2 was about 22 degrees IIRC and WTC1 was less.

3) The "progression" stage saw various medium to very large "sheets" of perimeter columns peel off and topple away. Can the software incorporate some pre-determined mix of sheet sizes OR actually use randomising?

So - just two questions:
(a) Do you agree that the sim should closely resemble the visual features actually seen on 9/11?
AND
(b) What are your thoughts on the 2-3 examples I suggested?

a) Yes of course. If it doesn't look like the
event, then the simulation isn't doing it's job properly. I have seen plenty of 'simulations' on YouTube which don't match reality. Granted they aren't on software fit for purpose - things like Teardown, Detonate or even the Hulsey/Fairbanks simulations which I actually don't consider to be a simulation. This is why I posted my video of Besiege here. I know it's far, far away from being close to reality, but for a £15 game it's a long way ahead of anything else out there.

b) I'll address these comments individually, but they are all valid points and perhaps highlight the most significant flaws in this software...

1) I completely agree, this is a flaw with Besiege. As far as I can tell, there's no way to connect the blocks to create the structure. This means as soon as there's any lateral movement the structure seems to break up. Not ideal. I'm still trying to hack into the code of the game, but so far the only thing I can find which might hold it together a bit better is a 'friction' parameter. If I can hack this value above what the in game settings allow, I might be able to create a better result here. But I agree, the software fails here.

2) Again this is a problem which is related to the above point, I can tilt the whole upper section of the structure manually, but the stability starts to break down. I am however going to try and to do a rough replication of the actual impact and column damage. From what I have done so far it's clear to me that WTC2 had less initial failure points in the initiation stage than WTC1. This (I think) explains the apparent pivot and subsequent tilt in WTC2. I haven't tested different percentages of failed columns yet, but that will be next on my list of things to try.
A sub point here is that my opinion is there were maybe 50-80% initial core column failure on WTC2, with the rest (on the west side) maybe holding out for a split second before they were completely overloaded by the tilt. WTC1 seems to be a much more uniform collapse, suggesting a much higher percentage of of simultaneous column failures. I have seen some videos suggesting a slight tilt to the South, so maybe some held out until they were overcome by the failure of the rest. This is just me thinking out loud here, I'm not sure if this has been discussed in this forum, but I'd be surprised if it hasn't.

3) This is another problem related to the above points. The software is rudimentary in that you can't create complex shapes. The only thing as I've mentioned above is the 'friction' parameter. This might be able to be used to 'attach' blocks together. With that said, as the blocks are technically indestructible and don't bend and deform the way steel does, so it's probably not going to be possible to replicate the 'peeling' of large sections as was seen in the real event.

As I've mentioned many times, this is far from perfect. However, for a consumer grade 'game' that only costs a few quid it does a pretty good job. I don't know of any other games that can process over 22,000 objects in this way.

At the end of the day though, it's not professional grade software, so it's not going to prove much, but it's all I have and I'm enjoying messing around with it.

I also mess around with some racing/motorsport simulators. In the same way that the ones I use are not multi million pound professional grade Formula 1 simulators, I can still have fun with them and get some interesting and realistic results which are impressive for an entry level user.
 
Last edited:

econ41

Senior Member
Thank you @dylbie - that post is a good overview of the barriers to presenting an accurate simulation. Especially when using modest level software. Just a couple of comments at this stage:
a) .... even the Hulsey/Fairbanks simulations which I actually don't consider to be a simulation.
The Hulsey "simulation" is based on true simulation but faked by cheating to force the outcome to meet the AE911 (T Szamboti) required outcome of "looking like" the real event. The NIST WTC7 sim doesn't "look like" the real event because the strains and deformations are exaggerated. A legitimate form of engineering sim BUT AE911 and other TM leaders have for years insisted that the NIST sim is wrong because it does not "look like" the real event. It actually does IF you understand engineering modelling but... So Hulsey was expected to produce a "looks like" simulation. Which he did by cheating. The topic has been extensively discussed in other threads on this forum if you want more details.
This is why I posted my video of Besiege here. I know it's far, far away from being close to reality, but for a £15 game it's a long way ahead of anything else out there.
Understood and agreed.
b) I'll address these comments individually, but they are all valid points and perhaps highlight the most significant flaws in this software...

1) ......I agree, the software fails here.
Also understood.
2) ....From what I have done so far it's clear to me that WTC2 had less initial failure points in the initiation stage than WTC1. This (I think) explains the apparent pivot and subsequent tilt in WTC2. I haven't tested different percentages of failed columns yet, but that will be next on my list of things to try.
That approach may help you to get better results out of the limitations of the software. It is not directly relevant to understanding the real event collapses. I may be able to help you improve your understanding of the real collapse mechanisms. It is easier to comprehend if you come from a broad brush big picture overview. The percentage of columns is not as directly relevant as your intuition seems to be suggesting.
A sub point here is that my opinion is there were maybe 50-80% initial core column failure on WTC2, with the rest (on the west side) maybe holding out for a split second before they were completely overloaded by the tilt. WTC1 seems to be a much more uniform collapse, suggesting a much higher percentage of of simultaneous column failures. I have seen some videos suggesting a slight tilt to the South, so maybe some held out until they were overcome by the failure of the rest. This is just me thinking out loud here, I'm not sure if this has been discussed in this forum, but I'd be surprised if it hasn't.
Good to see that you are trying to comprehend. Take care with any assumptions that core columns or perimeter columns somehow dominated the collapse and sort of acted as individual groups. Also take care with assumptions of "simultaneous collapse". The dominant part of the initiation mechanism was - without a doubt - a cascading failure - a sequential failure - of columns failing to support vertical axial loads. That process driven by load redistribution. (See the challenge posted at post #72 >> If you comprehend how load redistribution can multiply the load on a column to cause failure you will have one of the big "keys" to understanding.) (It could help to discuss that issue in more depth.)

3) This is another problem related to the above points. The software is rudimentary in that you can't create complex shapes. The only thing as I've mentioned above is the 'friction' parameter. This might be able to be used to 'attach' blocks together. With that said, as the blocks are technically indestructible and don't bend and deform the way steel does, so it's probably not going to be possible to replicate the 'peeling' of large sections as was seen in the real event.

As I've mentioned many times, this is far from perfect. However, for a consumer grade 'game' that only costs a few quid it does a pretty good job. I don't know of any other games that can process over 22,000 objects in this way.
Understood. BTW you don't need 22,000 objects to comprehend the real event. Sub-set the tower into a handful of sub-systems. maybe a dozen parts in a sub-system to illustrate principles. The reality of 22,000 objects is actually one of the main reasons FEA analysis of the whole system is impractical.

At the end of the day though, it's not professional grade software, so it's not going to prove much, but it's all I have and I'm enjoying messing around with it.

I also mess around with some racing/motorsport simulators. In the same way that the ones I use are not multi million pound professional grade Formula 1 simulators, I can still have fun with them and get some interesting and realistic results which are impressive for an entry level user.
Believe it or not I fully comprehend "messing around" with computers and software. Turn back the clock to 1965-6-7-8 and I was one of the leading computer hackers of that era in my organisation. 80 column punched cards. The "mainframe" had fully expanded core memory. 16K - yes "K". And yes - literally "core" - magnetic doughnuts threaded on a matrix of wire. And it was 16 decimal "K" - BCD addressing - and those bits of info will tell any other 80plus old farts what model the IBM computer was. ;) ;) So, by all means enjoy making the most out of the least capabilities of the software. I won't bore you with some of the tricks I played those 53 or so years back in a very different IT era.
 
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