# Use of Scale Model or Full Sized models for investigating 9/11 collapses

#### Mick West

Staff member
Violent destruction is not dis-assembly. The event was chaotic. How many models of chaotic events are modeled with any reliability?

All you need to determine is a rough range of models in which rapid progressive collapse occurs. It's obviously impossible to have every piece of steel end up in the same place. But it seem reasonable that a representative computer model building would fall down rapidly.

I'm sure it would be quite easy to get wrong though. I've had vast amount of experience of messing up simple physical modeling in games. Simple models introduce situations that don't exist in the physical world. It's a constant trade-off of accuracy against processor resources.

#### psikeyhackr

##### Member
All you need to determine is a rough range of models in which rapid progressive collapse occurs.

That means starting with the ASSUMPTION that the "collapse" could occur.

What we KNOW is that the structure could support itself against gravity. What we do not know is how much weight each level had to be strong enough to support. So the model must be vertical at the very least.

psik

#### jaydeehess

##### Senior Member.
Psikey, you need to decide if you are asking for simple demonstration of concept models or accurate modeling of the WTC tower collapses using accurate data such as the mass of components.

#### jaydeehess

##### Senior Member.
That means starting with the ASSUMPTION that the "collapse" could occur.

What we KNOW is that the structure could support itself against gravity. What we do not know is how much weight each level had to be strong enough to support. So the model must be vertical at the very least.

psik
Each "level" needed to support its own floor mass.

What you mean to ask is what load the column system at each vertical location along their length was capable of supporting.

As explained time and again, column failure was not the primary driver of collapse progression.

#### Keith Beachy

##### Senior Member
Violent destruction is not dis-assembly. The event was chaotic. How many models of chaotic events are modeled with any reliability?
Lots of them. Why would anyone model the WTC towers? What is the need?
One need is a clear zone if a building is compromised; and the FDNY knows when WTC 7 was not stable, they correctly cleared the area, and no one was killed or injured.
The WTC tower collapse has been modeled with math, the stucture of the WTC is known, and is easy to model (as in easy, for those who can and want to). A lot of people don't do math - and that would also be required for building a scale model.
Models of chaotic events.
http://www.avalanche.org/moonstone/zoning/avalanche dynamics.htm
http://large.stanford.edu/courses/2007/ph210/silverstein1/
http://www.pmmh.espci.fr/fr/morphodynamique/papers/A12_CRPhysique.pdf
http://www.physics.emory.edu/faculty/boettcher/Publications/papers/pre54_1082.pdf
Some chaotic events can be understood with scale models in a sense; in parts. Read the models for some ideas.

#### Jeffrey Orling

##### Senior Member
Beachy,
Interesting collection of papers... above my pay grade. I don't see scale models as much as these authors dealing with avalanche dynamics and how avalanches behave. Ironically I used the term vertical avalanche to describe what I saw in the twin tower collapse. I don't see this as applicable if the support of a structure is kicked out and it crushed apart on crashing with terra firma. Structures don't suspend themselves in mid air. The NIST 7wtc model is more of an avalanche than how I conceptualize what happened... I think that modeling the twin tower collapse is largely of no interest because once the tops of 10' of thousands of tons began to drop... no one doubts that every floor would be overwhelmed and any columns not broken apart in the collapse would fall from Euler instability. So there is hardly anything to model in the collapse phase.

The perhaps there is a need to understand the pre collapse phase with a model applying the energy inputs to the structure over time and see if that energy leads to disintegration of the tops. Do we need to model how heat would fail a steel frame and release the slabs and even parts of the frame from an integrated structural matrix? Maybe. It seems that engineers have understood how vulnerable steel is to heat and hence the fire protection and sprinkler systems to not only suppress fire but to cool the frame and prevent warping and runway failure of joints and destruction of integrity of the composites such as slabs and beams. Any rational person can see this wasn't fires of papers in trash bins burning on those floors.

I conclude there is little use in scale models to investigate the destruction of the towers... but perhaps study of the performance of isolated nodes within them... and those studies at full scale.

#### Jeffrey Orling

##### Senior Member
Each "level" needed to support its own floor mass.

What you mean to ask is what load the column system at each vertical location along their length was capable of supporting.

As explained time and again, column failure was not the primary driver of collapse progression.

Columns didn't participate in the collapse... they were the victims of it. In the twins for sure their failure at the top was part of the tops drop... but even those failures may likely have been from being pushed out of alignment (from expanding braces) and unable to do their thing.

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#### psikeyhackr

##### Member
Each "level" needed to support its own floor mass.

And you are implying what? Are you saying level 10 did not support levels 11 through 110?

What you mean to ask is what load the column system at each vertical location along their length was capable of supporting.

As explained time and again, column failure was not the primary driver of collapse progression.

You can CLAIM to have explained whatever you want. But the purpose of models is to determine what really happened.

psik

#### Mick West

Staff member
And you are implying what? Are you saying level 10 did not support levels 11 through 110?

The floors did not support the floors above them. The columns did.

Each floor could only support it's own static weight, plus a safety factor, and small dynamic loading.

So when a floor was hit with a big weight, it failed, stripping it away from the columns, leaving them unsupported sideways.

#### jaydeehess

##### Senior Member.
And you are implying what? Are you saying level 10 did not support levels 11 through 110?
I am pointing out that your wording is very nonspecific. When you press an elevator button to go to level 99 do you consider yourself as going to a specic location along the vertical supports of the structure, or are you going to the floor at that location?
Moreover I said "What you mean to ask is what load the column system at each vertical location along their length was capable of supporting.".
So my intent was quite clear.

In addition the load capability of a column at any specific location along its length is rather an odd thing to ask for. The core columns were made up of segments a max of 30 feet long ( that was the longest piece of steel that could be trucked into the construction site in the 70s) so columns spanned several floor heights. What the could support at the bolted connection to the next lower column would be their max load. However. The floors connected to it actually allow greater capacity by supplying lateral bracing as well as contributing to the load on the column by virtue of having their mass supported by the connections to the column.

If a column is braced and loaded and you simply take away the brace while still under the same load, the column will have a lesser capacity. Do the enough in a tall structure and the column will fail.
You can CLAIM to have explained whatever you want. But the purpose of models is to determine what really happened.

psik
So let's ignore all the questions of applicability and scaling and look at two models put forth already.
Well we have your column crush model then. It seems to demonstrate that column crush propagation would arrest.
Then we have Mick's model apparently demonstrating a floor connection failure will progress the entire height of a structure and the columns will fail as a consequence of that.
By that metric , floor collapse explains the progression of collapse since you apparently show column crush was not the mode of collapse.

In fact although you complain that there is no empirical evidence of floor collapse driven progression ( an incorrect assumption but let's give you that for the moment anyway), you have no empirical evidence to support the notion of column crush, or column failure by other direct means, dominated progression of collapse either.

Furthermore we do know that a sophisticated full scale computerized model of collapse initiation was performed that shows at the end of its simulated time period, massive overload of the floor/truss/connections was inevitable.
AND
There is no equivalently detailed model showing a progressive collapse accomplished by a column failure dominated mechanism. For instance , just as an example, no computer simulated model showing progressive column failure mechanism by use of explosive charges.

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#### Jeffrey Orling

##### Senior Member
JDH,
Some minor corrections to you excellent post. The columns were 36' length except all the corners were 24' or at the mech floor I think 28'... I am bit foggy about how the larger profile sections of the core fit to the smaller 36' sections below and above.

The column capacity I believe is not increased by bracing... but slender unbraced columns are weaker than than braced ones. The erection was designed for the connections to be above the floor level.. I think it was 3' which enabled workers to easily do the columns to column connections. The braces both held them in place laterally and supported the metal pans and the concrete which made up the floors inside the core. All local floor loads were applied to the SIDE of the columns via the bracing/beams... all loads... floor and columns themselves were applied axially. The collapse was the floors being ripped off and destroyed with little effect on the columns... and so column capacity in the collapse phase did not matter. Floor capacity did and the floors simply could not carry the excessive loads falling on them and the shattered and or the connections to the columns failed. All floors were the same so theoretically the height was immaterial... once the collapse of the floors started it would end when there were no more floors to crash / crush / shatter. There were virtually no slabs intact because the forces on them were like what happens when I grind a pill up in a mortar an pestle... the applied force of the pestle is more than the strength of the matrix of the "glue" (portland cement) which binds the pill or in the case of the concrete... the sand together.

You do not need to create a scale model for this... strength of concrete is well know.

As we saw the core survive and the facade fall away... the collapse is not mysterious at all. The core fell / toppled from (Euler) instability... excessive slenderness ratio... and the facade from the same.

Nothing to model... it's all settled engineering and physics...

"Building structures or large nonbuilding structures (such as dams and bridges) are rarely subjected to destructive testing due to the prohibitive cost of constructing a building, or a scale model of a building, just to destroy it."

"In destructive testing, or (Destructive Physical Analysis DPA) tests are carried out to the specimen's failure, in order to understand a specimen's structural performance or material behaviour under different loads. These tests are generally much easier to carry out, yield more information, and are easier to interpret than nondestructive testing. [1] Destructive testing is most suitable, and economic, for objects which will be mass-produced, as the cost of destroying a small number of specimens is negligible. It is usually not economical to do destructive testing where only one or very few items are to be produced (for example, in the case of a building). Analyzing and documenting the destructive failure mode is often accomplished using a high-speed camera recording continuously (movie-loop) until the failure is detected. Detecting the failure can be accomplish using a sound detector or stress gauge which produces a signal to trigger the high-speed camera. These high-speed cameras have advanced recording modes to capture almost any type of destructive failure.[2] After the failure the high-speed camera will stop recording. The capture images can be played back in slow motion showing precisely what happen before, during and after the destructive event, image by image."

" Destructive Testing

To find out how strong, resilient, flexible, or long-lived a material is often requires the ultimate sacrifice: the destruction of the sample by equipment and instruments designed to precisely measure its performance in the face of an overwhelming force.

Whether a sample is slowly pulled by tensile testing or subjected to sudden catastrophic impact, destructive tests can be the most economical and decisive ways to predict a material's capabilities and lifespan."

It's been done

#### psikeyhackr

##### Member
Psikey, you need to decide if you are asking for simple demonstration of concept models or accurate modeling of the WTC tower collapses using accurate data such as the mass of components.

When did you get appointed to telling me what I had to do?

I could drill holes in my washers to give the structure the exact same mass distribution as the north tower.

But in order to do that I would have to have the data. It is impossible to be accurate if one does not have the information to conform to.

So it is all the people who don't demand that information who are the problem.

The better the model the more informative it will be. But using tape as "floor connections" for two separate sticks that are supposed to demonstrate the effects of a single solid floor is hysterical.

psik

#### jaydeehess

##### Senior Member.
JDH,
Some minor corrections to you excellent post. The columns were 36' length except all the corners were 24' or at the mech floor I think 28'... I am bit foggy about how the larger profile sections of the core fit to the smaller 36' sections below and above.

The column capacity I believe is not increased by bracing... but slender unbraced columns are weaker than than braced ones. The erection was designed for the connections to be above the floor level..

I stand corrected on the length. If I'd written "~30 foot" it would have been better. My point was that it sometimes seems psikey believes the floors sat on top of column sections with the next column section on top of that floor and so on.
As for bracing, yes its a bit difficult for a non engineer/architect such as myself to express it properly. However I understand that all bracing does is prevent slender column buckling. I understand that these 36 foot long columns would probably not last long if simply raised into place and bolted down. The bolted connection would soon fail if the column were simply swaying alone. In essence the column would not be able to support any practical load. If you bolted three of these column sections together and put it vertical, even if the foundation connection is made infinetly strong, the column will not be able to survive its own mass load and will buckle.

However erect each of several columns and set temporary braces in place then connect them with floors and you can take a way the temp braces and continue moving up.
IN an ordered and well designed progression of construction.
Even single level wood frame houses go up one wall at a time with diagonal braces in place until the roof goes on to connect the walls together, then the diagonal braces can come off.
,,,,and that's a wall of studs, essentially a plane structure that is braced across the plane. It still requires the braces in the third dimension. If I make myself clearer than mud!

I think it was 3' which enabled workers to easily do the columns to column connections. The braces both held them in place laterally and supported the metal pans and the concrete which made up the floors inside the core. All local floor loads were applied to the SIDE of the columns via the bracing/beams... all loads... floor and columns themselves were applied axially. .........
It's been done
All good. I fully understand all of that, I and others have said it all along as have you. Its psikeyhacker that cannot seem to accept much of that.

#### jaydeehess

##### Senior Member.
When did you get appointed to telling me what I had to do?
So sorry ol' chap. Go right ahead continuing to conflate the issue of proper scale modeling of a specific structure with unscaled models that in no way resemble the structure you are trying to study.
Please allow me to reword the passage to:

Psikey, may I suggest that you decide whether you are asking for simple demonstration of concept models, or accurate modeling of the WTC tower collapses using accurate data such as the mass of components.
I could drill holes in my washers to give the structure the exact same mass distribution as the north tower
No, as pointed out, even if you had the same mass distribution, same percentage of mass between column and floors, same decrease in mass of column as height increases, you will not have a scale model since gravity and time don't scale down linearly.
But in order to do that I would have to have the data. It is impossible to be accurate if one does not have the information to conform to.
If you were to try to scale your model better you do not require exact data. Being precise in stitching will not help make a sow's ear a silk purse. If you want a silk purse then you need to precisely stitch silk.
I hope metaphor doesn't confuse you.

So it is all the people who don't demand that information who are the problem.
If someone wants to gather together a qualified group of respected engineers and re-run the same programs that NIST ran, and request the data set that NIST used, I would support that. If that group also wanted to review the data set and make recommendations on changes, I would support that IF they also then followed through by re-running the programs with said changes to see if it better matches observed events and thus is justifies accepting the changes.

But that's not what you are, nor is that what you are planning on doing.

The better the model the more informative it will be. But using tape as "floor connections" for two separate sticks that are supposed to demonstrate the effects of a single solid floor is hysterical.

psik
The hysterics seems to come mainly from you in this thread.
Your model is no better or worse a representation of the towers than ius Mick's model. Your complaining about the difference between his model and the towers while seemingly touting your model as demonstrating a concept in play in the towers is quite ironic. Almost enough to drive me into hysterical laughter.

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#### Jeffrey Orling

##### Senior Member
There is nothing to model that is already not settled engineering.

Who disputes that tens of thousands of tons of material cannot be supported by a twin tower floor slab? No one. If any truthers want to stand below a replica of a wtc OSS floor while it is loaded up with tens of thousands of tons... be my guest. You'll be crushed thinner than a crepe.

Who dispute that a steel column standing 600 feet tall made of 36' section one atop the other decreasing in size from 22x52 to 20x48 with 1/2" welded plates as splices will stand without toppling... 300 feet tall? Anyone who thinks these assemblies are stable can have a picnic next to one and also find themselves witness to thousands of tons falling down on them...

pskey wanna volunteer?

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#### Mick West

Staff member
The better the model the more informative it will be. But using tape as "floor connections" for two separate sticks that are supposed to demonstrate the effects of a single solid floor is hysterical.

But necessary in the absence of a 3D model, and in the absence of a model floor material that will break under the same scaled load.

Perhaps you could make the floors out of a thin layer of royal icing or something.

The tape is actually a reasonable approximation here, as it's strong enough to support a few times the mass of the floor - which is all that is asked of the floor supports in the actual towers.

##### Member
You'll be crushed thinner than a crepe.
But not blasted into tiny pieces that were found great distances from the site. However, that would be off topic.

I am not surprised that there is such a chorus of agreement here that the mechanic of the collapse event is so self explanatory that there is no need to demonstrate how it happened through modelling. Only Mick seems to admit the possibility, if not its necessity, although the reality is it has never been successfully done.

The rest of you seem terrified by the opportunity to have your certainties experimentally examined, and are busy finding objections to a project I think you should in principle welcome by filling your posts with appeals to authority and popularity.

Speaking for myself I would love to see a model -- verifiable by the likes of psikey as an acceptable simplification, of course -- that demonstrates how a structure such as the Towers could collapse so swiftly and totally. It would certainly serve as a useful piece of work to show those who are becoming persuaded by the work of David Chandler and others.

But it seems many here are scared by the dim possibility that the world may not be as flat as they think it is, and so would prefer to insist that big spheres can't possibly be on the horizon.

#### Mick West

Staff member
But it seems many here are scared by the dim possibility that the world may not be as flat as they think it is, and so would prefer to insist that big spheres can't possibly be on the horizon.

Nobody is scared, that's a silly characterization. I think it's more that they don't see a justification for doing it themselves. And why would they?

If, like most people, you don't find the collapse at all suspicious, then trying to verify this seems akin to setting up a camera in a fairy grotto to verify that there are no fairies. Of course it's still a useful exercise if you want to help people understand their reasons for suspicion are groundless, but it has little merit otherwise.

#### NoParty

##### Senior Member.
The rest of you seem terrified by the opportunity to have your certainties experimentally examined, and are busy finding objections to a project I think you should in principle welcome by filling your posts with appeals to authority and popularity.
I don't sense that anyone here is "scared" to see a thoroughly realistic and relevant model re-enact the collapse.

Personally, I'd love to watch it.

On someone else's dime, of course.

I don't find the actual collapse confounding, unresolved, sinister, or even surprising, circa 2014, but if anyone does
--and feels strongly enough to spend a lot of money on a re-creation, please invite me! I want front row seats.

p.s. You did not really type "...verifiable by the likes of psikey..." did you?

#### econ41

##### Senior Member
But not blasted into tiny pieces that were found great distances from the site. However, that would be off topic.
It is a different topic to what is being discussed here - but by all means raise it in an appropriate thread and I will discuss it with you.
I am not surprised that there is such a chorus of agreement here that the mechanic of the collapse event is so self explanatory that there is no need to demonstrate how it happened through modelling. Only Mick seems to admit the possibility, if not its necessity, although the reality is it has never been successfully done.
Your are misunderstanding or misrepresenting the situation with the collapse events and status of recent discussion.
There is no chorus of agreement that "...the collapse event is...self explanatory..". You are conflating two different stages of event and two different target audiences. Only the mechanism of "progression" stage could be self explanatory. And that only to persons possessed of the appropriate skills at physics - what I identified as the "professional audience". Both Mick and I agree that models of the progression stage could be useful to persons who do not have those skills - those who I identified as the "lay audience". (Others may agree but most have not explicitly either agreed or disagreed.)

Nor is there any chorus of agreement "that there is no need to demonstrate how it happened through modelling". The only option where there is simply "no need' is with the progression stage where there is IMO no need for professional audiences to have a quantifiable model. There could be a valid need for a visual demonstration model - "qualified" but not "quantified" - for lay audiences.

The area where Mick and I are still at some difference - so far in this discussion - is that he sees the potential for more powerful computers to provide more detailed and more precise results. I don't dispute that aspect and have not commented on it so far. BUT I hold two reservations.
• First I doubt that the engineering is achievable irrespective of computer power for the collapse stage where such details could be of value to professionals. The more precise data is simply not available to improve accuracy of details. Two extra limits are subsumed there but I'll step over them for now.
• Second is that the extra precision would be at the level of WTC specific details where I hold that those details are of little value for designers of future buildings. AKA the valid need of the engineering profession.

I hold no doubt that current iT graphical technology and skills could produce dynamic visual models suitable for lay persons. (and possibly of interest to professionals.) BUT these could not be numeric quantifying models.

The rest of you seem terrified by the opportunity to have your certainties experimentally examined, and are busy finding objections to a project I think you should in principle welcome by filling your posts with appeals to authority and popularity.
I have zero fear or "terror". I have stated my professional engineering opinions explicitly. They do not go to - do not need to go to - "[having my] certainties experimentally examined". Yes I have made claims based on appeals to my personal authority as an engineer. I stand by those claims and will defend them if properly challenged. Step one for such a challenge from yourself would be when you desist from conflating those incompatible aspects which I have already explicitly distinguished. THEN state your objection to my appeal to my own authority and I will respond.
Speaking for myself I would love to see a model -- verifiable by the likes of psikey as an acceptable simplification, of course -- that demonstrates how a structure such as the Towers could collapse so swiftly and totally. It would certainly serve as a useful piece of work to show those who are becoming persuaded by the work of David Chandler and others.
Three separate aspects viz:
• You qualify as a lay person benefactor of the visual explanatory models I have agreed have a need;
• psikey has been declining challenges to his claims since 2007 (My own personal experience) AND conflation of "models of a different mechanism" with "implied claims about real event" has been a consistent feature of his claims. Confirmation of the aspects you refer to by psikey is unlikely.
• You refer to "collapse so swiftly and totally". That refers to the progression stage where I have now repeatedly stated that a visual model could be of some value for lay audiences AND would be of no value - unnecessary - for professional audiences. By all means feel free to identify a legitimate professional need that I have either overlooked or not explained already;
• Take care with yet another conflation (change of focus) The work of Chandler relates to initiation stage NOT "progression".
But it seems many here are scared by the dim possibility that the world may not be as flat as they think it is, and so would prefer to insist that big spheres can't possibly be on the horizon.
Evasive hyperbole. My position is clear and I can defend it. Ball in your court if you wish to disagree with what I have actually claimed.

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#### Mick West

Staff member
The area where Mick and I are still at some difference - so far in this discussion - is that he sees the potential for more powerful computers to provide more detailed and more precise results. I don't dispute that aspect and have not commented on it so far. BUT I hold two reservations.
• First I doubt that the engineering is achievable irrespective of computer power for the collapse stage where such details could be of value to professionals. The more precise data is simply not available to improve accuracy of details. Two extra limits are subsumed there but I'll step over them for now.
• Second is that the extra precision would be at the level of WTC specific details where I hold that those details are of little value for designers of future buildings.

Yes, there are limits on how accurately the input data can conform to the conditions on the day. However, I don't think that's there's a simulation that has reached those limits yet. You've just got to look at the WTC7 simulation, where connections were modeled as simple constraints and limits, rather than high resolution FEM models of the girders, beams, plates, and nuts and bolts - not to mention the concrete, and then the air, with it's entrained dust.

Of course the abstractions are generally good enough for a representative model - certainly enough to determine the safety of a building. But there's near infinite room for more detail.

##### Member
I'd just like to see the collective effort of this thread directed towards what would really be required to make such a model. Again, is all the information required fully in the public domain? Jeffrey, you seem to think not: as Mick asks, what is it that cannot be done without the missing information? Can an acceptable model be made without the structural drawings? Is there some way that they might be obtained?

And yes, I do think a standard of verification that can be agreed by all "sides" of the debate is important. Again, that is the point of an open source model. The Towers were finite structures so there must be points of agreement on the nature of their construction that can be achieved in discussions of this nature. It's just a matter of the availability and provenance of data, isn't it?

Mick, people once thought electricity was magic when it appeared in the form of lightning, but eventually the phenomenon was reproduced and controlled under laboratory conditions. Comparing skepticism about the mechanic of the Towers' collapse to a belief in fairies is simply not good enough as long as all attempts to reproduce and demonstrate the dominant theory have failed.

#### Mick West

Staff member
Mick, people once thought electricity was magic when it appeared in the form of lightning, but eventually the phenomenon was reproduced and controlled under laboratory conditions. Comparing skepticism about the mechanic of the Towers' collapse to a belief in fairies is simply not good enough as long as all attempts to reproduce and demonstrate the dominant theory have failed.

I disagree. Again it comes down to the need to reproduce what we saw. It's very much like asking someone who does not believe in fairies why they don't spend more time trying to disprove fairies, when all other attempts to disprove fairies have failed.

What is needed here is a good reason to suspect something. Which is why the onus here is on the truther community to do something.

There's simply no pressing perceived need from non-truthers. So y'all telling us repeatedly we need to prove something is a little bemusing. It's YOU who need to prove something.

##### Member
In my view -- within the context of this thread -- the onus is shared equally between the two groups (although I do not recognise a binary opposition in this question). You may believe the mechanic of collapse is self evident, but you cannot demonstrate or reproduce it, or at least have failed so far to do so. Others may think it is impossible, but again the model has not been attempted.

It seems to me that it is in the interests of both parties to demonstrate their ideas, but the weight of experimental evidence most certainly does not rest on your "side" any more than it rests on the "side" of the "truther community".

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#### Mick West

Staff member
In my view -- within the context of this thread -- the onus is shared equally between the two groups (although I do not recognise a binary opposition in this question). You may believe the mechanic of collapse is self evident, but you cannot demonstrate or reproduce it, or at least have failed so far to do so. Others may think it is impossible, but again the model has not been attempted.

It seems to me that it is in the interests of both parties to demonstrate their ideas, but the weight of experimental evidence most certainly does not rest on your "side".

But since the non-truther side is not going to do anything about making a model, then where does that leave you?

##### Member
It leaves me curious as to whether or not a credible model of the most catastrophic structural failures in history can be made -- and of the view that such a project should not be an impossibility, given time.

#### econ41

##### Senior Member
Yes, there are limits on how accurately the input data can conform to the conditions on the day. However, I don't think that's there's a simulation that has reached those limits yet. You've just got to look at the WTC7 simulation, where connections were modeled as simple constraints and limits, rather than high resolution FEM models of the girders, beams, plates, and nuts and bolts - not to mention the concrete, and then the air, with it's entrained dust.
Fully agreed. The issue I raise is not the possibility of doing it. Rather whether or not it serves any purpose other than showing it can be done.

We are a long way from IBM1620 days and the IBM1401 - its commercial peer in time. I learned "hacking" on the 1401 before the term became common use (1967-8) - I could still write "machine language code" on paper if tried.

Was offered a 1620 about 25 years back - "Come and take it and it is yours". Didn't have a spare garage and already had a PC, table top size and several times more powerful.

Of course the abstractions are generally good enough for a representative model - certainly enough to determine the safety of a building. But there's near infinite room for more detail.
Agreed on all three points. I don't see a need for more detail. Especially within the scope of this OP - 9/11 WTC investigation. Professional inquisitiveness is a different matter. And - for the engineering aspects - deciding what you want to understand better comes before asking if a model would help. I still suspect "no".

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#### Mick West

Staff member
Agreed on all three points. Don't see a need for more detail. Especially within the scope of this OP - 9/11 WTC investigation.

The "need" is in convincing those who say the model is not detailed enough. Not a pressing need.

Consider the issue of the seated connection with stiffener plate in WTC7. This was modeled in the global model as an abstract connection with simple failure when walked off, and then also modeled without a stiffener plate in the more detailed local model. So both models were criticized.

There's also the possibility that a more detailed model might reveal something interesting about the collapse - perhaps some unanticipated failure mechanism of connections, or some emergent compound behavior of some system. But again, no pressing need. However it might be interesting in 20 years when computing power is cheaper and you can rapidly iterate variations. You'll probably also have some AI to help you with the modeling too.

#### econ41

##### Senior Member
It leaves me curious as to whether or not a credible model of the most catastrophic structural failures in history can be made -- and of the view that such a project should not be an impossibility, given time.
I'm confident that I understand your position. However:
1) A credible model of the total mechanism is not feasible at present.
2) Feasibility is not likely to change.
3) Whether or not it becomes possible for whom do you want it modelled? Professionals or lay persons? Implicitly it is for YOUR benefit..
4) If it is for you - apparently a lay person - then modelling outline explanations via computer graphics is plausible now. But unlikely that anyone will do it for you. So you are stuck with needing to understand what has already been explained.
5) The process would be ironic if you - hypothetically - chose to become an engineer. Once you gained the engineering expertise you would then understand why you didn't need a model of progression and why a professional level model of "initiation" is not possible.

#### econ41

##### Senior Member
The "need" is in convincing those who say the model is not detailed enough. Not a pressing need.
Yes

Consider the issue of the seated connection with stiffener plate in WTC7. This was modeled in the global model as an abstract connection with simple failure when walked off, and then also modeled without a stiffener plate in the more detailed local model. So both models were criticized.
One of those bleedingly obvious situations where in polarised debate BOTH SIDES miss false premise assumptions. In this case unproven premises. The idea that in a heat ravaged building the "offending component" should behave in certain ways measured to fractions of an inch. Whilst presuming that the adjoining columns and framing remains totally unmoved in its original locations unaffected by heat. And nobody on two other forums wants to here that - too busy enjoying arguments.

There's also the possibility that a more detailed model might reveal something interesting about the collapse - perhaps some unanticipated failure mechanism of connections, or some emergent compound behavior of some system. But again, no pressing need. However it might be interesting in 20 years when computing power is cheaper and you can rapidly iterate variations. You'll probably also have some AI to help you with the modeling too.
Yes. I think we are on the same sheets of music.

I doubt there is anything further of on topic value I can add at this stage. So let's see what emerges.

##### Member
1) A credible model of the total mechanism is not feasible at present.
A credible model of the general mechanism is feasible, as I think others on this thread agree. Beyond this is a discussion of resources.
2) Feasibility is not likely to change.
It is feasible already, as I think others on this thread agree.
3) Whether or not it becomes possible for whom do you want it modelled? Professionals or lay persons? Implicitly it is for YOUR benefit..
Everyone. The distinction is irrelevant.
4) If it is for you - apparently a lay person - then modelling outline explanations via computer graphics is plausible now. But unlikely that anyone will do it for you. So you are stuck with needing to understand what has already been explained.
You were just saying it wasn't feasible, but now you're simply guessing I don't have the capacity. Models are about demonstrating understanding and explaining phenomena experimentally. You are as much a failure in this respect as I am.
5) The process would be ironic if you - hypothetically - chose to become an engineer. Once you gained the engineering expertise you would then understand why you didn't need a model of progression and why a professional level model of "initiation" is not possible.
Patronising nonsense.

#### econ41

##### Senior Member
A credible model of the general mechanism is feasible, as I think others on this thread agree. Beyond this is a discussion of resources.

It is feasible already, as I think others on this thread agree.
Everyone. The distinction is irrelevant.
You were just saying it wasn't feasible,
You continue to rely on conflation. My points of assertion have been made AFAICS with clear distinguishing of the several factors which you persist in conflating.
Feel free to address the technical issues of topic which I actually made.

#### jaydeehess

##### Senior Member.
It leaves me curious as to whether or not a credible model of the most catastrophic structural failures in history can be made -- and of the view that such a project should not be an impossibility, given time.
If it is going to be done the most likely group to do it will be those who do not accept the explanation of the global collapse.

Picture yourself as an engineer who accepts what is sometimes refered to as ROOSD as the primary mechanism of tower collapse.

What motivates such a person to spend time and resources on new modelling?

#### psikeyhackr

##### Member
The floors did not support the floors above them. The columns did.

Each floor could only support it's own static weight, plus a safety factor, and small dynamic loading.

That is why I say LEVEL and not FLOOR.

By LEVEL I mean a 12 foot high horizontal slice through the building. From the plane defined by the surface of one floor to the plane defined by the surface of the next, including everything in the core and the perimeter columns. You are not saying anything I don't know.

But when do you explain how a floor could fall and remain perfectly horizontal? Wouldn't all of the connections have to break simultaneously? But if the floor tilts wouldn't it squeeze the core thereby creating lots of friction and slow things down? How did the north tower come down in 25 seconds?

So let's see a model that can do it.

psik

#### psikeyhackr

##### Member
No, as pointed out, even if you had the same mass distribution, same percentage of mass between column and floors, same decrease in mass of column as height increases, you will not have a scale model since gravity and time don't scale down linearly.

My model is small enough to fit into a centrifuge. But the point was to be as weak as possible. Using a centrifuge would mean having to make the loops stronger to hold the increased "weight". It tends to cancel out.

It sounds like you need to come up with excuses to not do a model. But the gravity scaling business doesn't apply to computer simulations. You don't appear to be enthusiastic about those either.

psik

#### Mick West

Staff member
But when do you explain how a floor could fall and remain perfectly horizontal?

The floors broke up and fell in pieces. There was a lot of weigh on them, it was not even.

The floors are not like your washers.

#### Oystein

##### Senior Member
if the floor tilts wouldn't it squeeze the core ...? How did the north tower come down in 25 seconds?
I don't understand what you mean "squeezing". Care to elaborate? How would floor tilt lead to more friction on the core?

##### Member
You continue to rely on conflation.
Your false dichotomy serves no apparent purpose except to allow you to expel a fetid air of superiority at fatuous length. If you are as qualified as you claim, contribute something useful to the discussion: for example, how a model could be made or what simplifications might be acceptable.
Picture yourself as an engineer who accepts what is sometimes refered to as ROOSD as the primary mechanism of tower collapse. What motivates such a person to spend time and resources on new modelling?
I picture you as an astronomer in the geocentric age. What motivated Copernicus to create the heliocentric model?

#### Oystein

##### Senior Member
...
I picture you as an astronomer in the geocentric age. What motivated Copernicus to create the heliocentric model?
False analogy.

Remember, we are here discussing models for the towers, to then observe their behaviour.
When you claim [STRIKE]econ[/STRIKE] jaydee is "in the geocentric age" and that Copernicus went ahead and came up with a more correct model, you imply that his model of the universe is wrong. If your analogy were a true analogy, then you'd further imply that his model of the towers is wrong. I don't think this is what you mean. You mean to imply that econ's (supposedly valid) tower model, if done, would behave differently than he thinks.

But you wrote this analogy in reply to "ROOSD as the primary mechanism". ROOSD is mostly a description of the actual collapse - it's a matter of observation, not of theory or model, that the actual vertical collapse progression was mostly a series of floor failures (disconnecting from columns) inside of the building perimeter, followed by wall sheets peeling off.

Conceptually, it is very easy to understand that the bulk of the falling mass, including both already acreted floor sheets and column assemblies, would impact floors, creating dynamic loads that far far exceed floor capacity. It is therefore both intuitively and analytically clear that collapse cannot be arrested once some threshold of downward "momentum" (I am using the term losely - meaning some combination of falling mass and velocity thereof, not necesscarily the product of the two) has been achieved.

Do you claim that "ROOSD" is a false model / description of the actual collapses observed on 9/11?
Or do you claim that [STRIKE]econ's[/STRIKE] jaydee's tower model is / will be false?

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#### econ41

##### Senior Member
Your false dichotomy serves no apparent purpose except to allow you to expel a fetid air of superiority at fatuous length. If you are as qualified as you claim,...
Personal comments noted. What "false dichotomy" do you refer to?
....contribute something useful to the discussion: for example, how a model could be made or what simplifications might be acceptable.
I have already contributed useful input into the discussion by clarifying the four main situations where models could be applicable. If you disagree with those as the main aspects please say:
a) Why those two aspects - four options - are inappropriate; AND
a) Provide your own suggestions as to how the different areas of application might be distinguished.

Also I have already identified at least two examples of where "a model could be made or what simplifications might be acceptable". if you disagree with those two feel free to say what your disagreement is and why. OR identify any other areas - other than the ones I have identified - where you consider modelling could be appropriate.

I have also identified examples of where and why I consider models would either not be possible or would not serve useful purposes. If you think my assessment is is wrong please say where and why.