How could the interior collapse in WTC7 Move West Without More Visible Exterior Damage

Floor/perimeter connections would have to carry diagonal and horizontal loads lost by perimeter frame vertical breach
So the floors unzip from the breach?

So the point of a vertical breach is to cause many floors to unzip?

Besides, how do we even know that the floors separated - except in the NE quadrant? We know that when the perimeter frame fell, the west penthouse was still visible.

know the east half of the structure was leaning to the north because the first move of the perimeter frame was for the east half to fall north, with no down motion.
No we dont. A collapse in the NE may cause southward seat due to the shift of CG.

What does it have to do with the gash anyway?
 
(how we know there was a vertical breach?)
1. The perimeter frame fell over in two opposing directions.
2. There was no reaction in the SW corner to the NE corner motion; not at onset and not later in collapse.
I think this is one of those "right for the wrong reason" cases.

There was a gash - it was photographed. But the non-coupling of the NE and SW horizontal motion cannot be soundly attributed to the gash - yet. The more obvious explanation to me is that it was because there was a void adjacent to the NE corner, because as is well known, the floors were gone.
 
If the lack of exterior damage during the collapse plainly follows from physical principles and the structure of the building, how is it that NIST were unable to recreate it in any of their simulations? They did several different scenarios, all of which showed the exterior warping greatly as the interior collapses. It's the least pronounced in the final one with both impact and fire damage considered, but I believe this is due to that simulation cutting so early. If they just rendered more frames, I'm sure the outside walls would have flopped all over the place, just like in the other simulations. This leaves two options:

1) Their modelling was wrong. In reality, the exterior was much more rigid than in their model, which made it stand firm as the interior collapsed. But if this was the case, why didn't they just fix it?

2) Their scenario of how the building collapsed didn't happen.
 
This leaves THREE options:

1) Their modelling was wrong. In reality, the exterior was much more rigid than in their model, which made it stand firm as the interior collapsed. But if this was the case, why didn't they just fix it?

2) Their scenario of how the building collapsed didn't happen.
3) Far too many people don't understand the visual limitations of the NIST simulations.

And remember the tricks Hulsey and AE911Truth played with the false dichotomy. Just because the NIST sim doesn't "look like" the real event DOES NOT PROVE that the fraudulent Hulsey sim is correct even tho it is faked to "look like" the real event.
 
As the proximate cause was heat... it likely was widespread enough to impact multiple beams and connections. I suspect the heat acted in a way analogous to water boiling... once water reaches the boiling point its state radically changes. The structure degradation was likely reasonably local and significant enough to trigger a runaway progressive collapse with the help of the structural design. Designs are intended to relocated load paths in the case of failures. But enough loss of load paths would leave the building incapable of self support.
 
3) Far too many people don't understand the visual limitations of the NIST simulations.

And remember the tricks Hulsey and AE911Truth played with the false dichotomy. Just because the NIST sim doesn't "look like" the real event DOES NOT PROVE that the fraudulent Hulsey sim is correct even tho it is faked to "look like" the real event.
Well so, what is your understanding of why the exterior becomes so damaged in the NIST simulations, but not in reality? Like what is the problem, or "visual limitation" that makes it so they couldn't make it match?
 
The gross deformations seen in the NIST simulation are far greater than the ductility limits of the materials would allow. Therefore the sim is calibrated to show the direction of strain motions NOT their magnitude. It is an aspect of simulation similar to scale factor effects- The sim methodology is not intended to visually "look like" the real event.
If you comprehend that aspect and reason from there the other apparent issues should fall into place and resolve the confusions.

THEN - the Hulsey fraudulent simulation was premised on fooling gullible truthers. Those who do not understand the issues of "visual look alike" that apply to simulations. "Truthers" have been indoctrinated with the belief that a simulation is not valid if it doesn't "look like" the real thing. Which may be true - it is situation specific. Hence the claims are lies by partial truth.
 
The gross deformations seen in the NIST simulation are far greater than the ductility limits of the materials would allow. Therefore the sim is calibrated to show the direction of strain motions NOT their magnitude. It is an aspect of simulation similar to scale factor effects- The sim methodology is not intended to visually "look like" the real event.
So they could have just turned off that calibration, and the simulation would have looked more like the real thing? I would like to see that.
 
So they could have just turned off that calibration, and the simulation would have looked more like the real thing?
Possibly. We don't know if the simulation was accurate on all the other factors - my comment only goes to the one aspect causing confusion.
And we seem to have no clear understanding of what the purpose of these discussions is.
I would like to see that.
That's your choice. I have little interest in chasing issues that have no demonstrated relationship to a defined topic of discussion.
 
Therefore the sim is calibrated to show the direction of strain motions NOT their magnitude. It is an aspect of simulation similar to scale factor effects-
If they exaggerated the lateral deformations of the perimeter, then

Why not present a direct quote from their paper?

And why don't we see the building falling over to the south?
Screenshot_2022-04-04-16-38-39-473_com.microsoft.office.word-01.jpeg
 
@econ41 As I see it, the two gross deformations are to scale, and are the result of actual errors in the simulation. But the real question is whether these errors matter.

I would argue that the only error that matters is the one in the NE. This is where the initial failure occurred.

The greater inward bowing here is not due to greater pull in forces, but due to these forces being applied for longer. This in turn is due to the overestimated extent of the floor collapse. In reslity, only columns 79 and 80 failed. The shorter levee arm, aling with the much more rigid restraint in the south, caused pull in forces to increase to failure at a smaller displacement - before the columns had been bent to buckling.

This is indeed Nordenson's version.
Screenshot_2023-01-17-08-36-23-576_com.microsoft.office.word-01.jpeg
 
Possibly. We don't know if the simulation was accurate on all the other factors - my comment only goes to the one aspect causing confusion.
And we seem to have no clear understanding of what the purpose of these discussions is.
I just don't think this makes much sense at all... That they could have rather simply made a simulation that more accurately replicated the lack of deformation in the exterior, but chose not to for some vague, science-y reasons. Do you agree with these two points:

1) Their model of the building accurately replicates the structure of WTC 7.
2) Their simulation software accurately simulates reality.

If those two points are true, I don't understand why it would be unreasonable to want to see the simulation match the real event. Your idea that they would deliberately exaggerate the motions of the exterior so it no longer matches is nonsensical to me.
 
I just don't think this makes much sense at all... That they could have rather simply made a simulation that more accurately replicated the lack of deformation in the exterior, but chose not to for some vague, science-y reasons. Do you agree with these two points:

1) Their model of the building accurately replicates the structure of WTC 7.
2) Their simulation software accurately simulates reality.

If those two points are true, I don't understand why it would be unreasonable to want to see the simulation match the real event. Your idea that they would deliberately exaggerate the motions of the exterior so it no longer matches is nonsensical to me.
This has been covered. Your personal incredulity is not the standard.
 
As for discussing the details of how, in the NIST simulations, the WTC7 perimeter is distorted: Be cautious.

We cannot hope to ever simulate the real collapse to an arbitrarily fine level of detail without knowing far better than we possibly can the starting conditions.
And this is the best reason why NIST should not even have tried to replicate the behaviour of the shell, as indeed I assume they DID not really try.

The question NIST sought to answer was NOT "can you replicate in great accuracy the collapse of the walls?"
The real question was: "Can the initial, local failures predicted by the ANSYS model result in a progressive collapse of the whole thing, as observed?" where the "as observed" part includes the major steps: 1. East core drops as a unit, 2. West core drops as a unit, 3. Perimeter drops as a unit.

(No, I do not cite NIST's objectives here; I do not even paraphrase them. This is to save me and you a bit of time. I assume we are already on the same page here, that, essentially, you all agree that this is what NIST did and did not go after. Challenge my assumption, if you must, and I can dig for the cites)

Remember that NIST published animations of two main global collapse runs: One WITH initial damage from debris impact, one WITHOUT such initial damage.
I hope you all recall that the latter resulted in a collapse with very gross deformations of the entire building's shell, while the former resulted in a "tamer" collapse with less distortion of the shell and thus much more "like" the collapse filmed in reality.
The thing here is that no one knows the exact extent of prior damage! NIST only plugged in the damage that is documented in images, in addition to damage in the lower 14 floors of the East core as results from the ANSYS simulation. But there were large parts of the building's shell that no camera ever captured after the fall of the North Tower, and there surely was also accrued structural damage from fires in the West core, and above the 16th floor, that NIST did not model.
And so even the simulation WITH impact damage is a WRONG model because it starts out with TOO LITTLE damage.
But seeing how wildly different the "with" and "without" impact damage animations are, it stands to reason that correcting the model "with" damage, albeit too little and perhaps some wrong damage, with a model run that has all the right (alas unknowable) damage would look quite different still, and would, or would perhaps not, resemble the real collapse even better.

In any case, the point remains: Because it makes, obviously, a significant difference for the LS-DYNA model whether and what initial damage you put in, and because we cannot and do not know the actual amount and nature of initial (and accrued) damage, we MUST expect the LS-DYNA simulaton to be visibly different from the real collapse - and so there being a difference is not a legitimate ground to dismiss the NIST animation wholesale.
NIST got the main features right.

(And since the Hulsey study has been brought up as a reference, a quick reminder of the main difference between NIST's and Hulsey's animations:
  • In the NIST report, the individual failures, their timing and the eventual collapse animation are the RESULT of an unbroken chain of causes and effects, starting with the structure as built minus impact damage plus initial fire location, through a realistic fire simulation with realistic fuel loads, through a full simulation of rising and falling temperatures in the structural materials as fires come and wane, through a detailed tallying of structral damage that accrues as a result of that heating, and how connection strength is impacted, how beams expand and contract, and sag, and through a full dynamic 47-floor model that takes all the results of the prior modelling - AND NOTHING MORE. This model in fact explains the final collapse sequence as a result of physics running its course from true starting conditions.
  • In the Hulsey model, there is the structure as built, but he models no initial damage, no fires, no heating, no accrual of connection damage - and then makes disappear, as if by magic, entire columns, many of them, at the times he needs to remove them to mimick the outer appearance of the collapse. This is an appeal to magic (or to "demolition devices" of which there is neither evidence nor even a theory) and entirely non-explanatory: The removal (failure) of columns here is not a result of the modelling, it's input to the model.
 
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