NIST WTC7 computer animation question
- Thread starter Edx
- Start date
Quick answer, because simulating this kind of thing is incredibly difficult.
If you were to reassemble WTC 7 a hundred times, start exactly the same fires in it each time, and then wait for it to burn out, you would not get the same collapse each time.
Should be no surprise. Suppose you drop a bottle on the concrete. Sometimes it breaks. Sometimes it doesn't. Sometimes it just cracks, and sometimes it shatters completely. This is true even if you repeat the conditions as perfectly as you can. The collapse of a large, complex, damaged building is many millions of times more complicated.
This kind of system follows a science called deterministic chaos. Even very small changes in behavior, early on, can lead to visible and seemingly large changes later. Say a weld hangs on for half a second longer than it did last time. Suppose these four bolts don't all let go at the same time. Suppose a column fragment just happens to get wedged between two large pieces and absorbs energy as it flexes, instead of just spearing through the debris.
You can see this effect clearly in the Purdue study of WTC 1 and WTC 2. They ran their simulations dozens of times, making tiny variations in the impact damage, the failure strain of materials, and so on, and found there are quite a few differences between runs. Nobody has bothered to do the same for WTC 7 that I know of, but it certainly could be done. I'd recommend anyone interested contact Dr. Irfanoglu at Purdue and start working on an NSF grant.
Now, having said that, the varying WTC 1 and WTC 2 results do have some features in common -- like the fact that virtually all of them do lead to a collapse. That's what these simulations are for. They aren't intended to make things look exactly right. They're intended to provide some insight into the mechanisms of failure, and to determine whether a given hypothesis is plausible.
And that's all NIST does with WTC 7. Their result did not depend on the exterior collapse simulation. Had this happened in the 1990's, the simulation itself would have been impossible! We wouldn't have simply thrown up our hands and said, "gee, we don't have a fast enough computer, guess we'll never know. Could have been fire, and could have been aliens." Indeed, you could remove that entire chapter of the WTC 7 report and lose almost nothing.
What they did, instead, was to set up two trials with different conditions, and see which one was a better fit to what actually happened. This was a quick way to estimate whether the impact damage had any effect on the collapse. And the answer is, yes, it does -- although they also found it's not likely the collapse would have happened any sooner as a result of that damage. But neither case is a perfect match, nor does it need to be.
Truthers whining about how it "looks different" are following the call to perfection logical fallacy. They arbitrarily decide how perfectly they want things to fit, and then complain when their threshold isn't met. You will note that there is no professional complaint about the fidelity of the WTC 7 simulations. Those who understand the report, and why the sim was run in the first place, also understand that a perfect visual match is not expected nor necessary.
Truthers use "call to perfection" all the time -- show us aircraft debris with serial numbers, they say. Show us a video of the Pentagon impact. Show us the total mass of recovered debris near Shanksville. Well, you don't get to make those demands. If we applied them to the Truthers, they'd be silent forever. To wit: Show us your hypothesis. Show me that you aren't Paul Doherty. Show me that you actually believe the crazy things you're typing on the Internet. Can't do it, can you?
If you were to reassemble WTC 7 a hundred times, start exactly the same fires in it each time, and then wait for it to burn out, you would not get the same collapse each time.
Should be no surprise. Suppose you drop a bottle on the concrete. Sometimes it breaks. Sometimes it doesn't. Sometimes it just cracks, and sometimes it shatters completely. This is true even if you repeat the conditions as perfectly as you can. The collapse of a large, complex, damaged building is many millions of times more complicated.
This kind of system follows a science called deterministic chaos. Even very small changes in behavior, early on, can lead to visible and seemingly large changes later. Say a weld hangs on for half a second longer than it did last time. Suppose these four bolts don't all let go at the same time. Suppose a column fragment just happens to get wedged between two large pieces and absorbs energy as it flexes, instead of just spearing through the debris.
You can see this effect clearly in the Purdue study of WTC 1 and WTC 2. They ran their simulations dozens of times, making tiny variations in the impact damage, the failure strain of materials, and so on, and found there are quite a few differences between runs. Nobody has bothered to do the same for WTC 7 that I know of, but it certainly could be done. I'd recommend anyone interested contact Dr. Irfanoglu at Purdue and start working on an NSF grant.
Now, having said that, the varying WTC 1 and WTC 2 results do have some features in common -- like the fact that virtually all of them do lead to a collapse. That's what these simulations are for. They aren't intended to make things look exactly right. They're intended to provide some insight into the mechanisms of failure, and to determine whether a given hypothesis is plausible.
And that's all NIST does with WTC 7. Their result did not depend on the exterior collapse simulation. Had this happened in the 1990's, the simulation itself would have been impossible! We wouldn't have simply thrown up our hands and said, "gee, we don't have a fast enough computer, guess we'll never know. Could have been fire, and could have been aliens." Indeed, you could remove that entire chapter of the WTC 7 report and lose almost nothing.
What they did, instead, was to set up two trials with different conditions, and see which one was a better fit to what actually happened. This was a quick way to estimate whether the impact damage had any effect on the collapse. And the answer is, yes, it does -- although they also found it's not likely the collapse would have happened any sooner as a result of that damage. But neither case is a perfect match, nor does it need to be.
Truthers whining about how it "looks different" are following the call to perfection logical fallacy. They arbitrarily decide how perfectly they want things to fit, and then complain when their threshold isn't met. You will note that there is no professional complaint about the fidelity of the WTC 7 simulations. Those who understand the report, and why the sim was run in the first place, also understand that a perfect visual match is not expected nor necessary.
Truthers use "call to perfection" all the time -- show us aircraft debris with serial numbers, they say. Show us a video of the Pentagon impact. Show us the total mass of recovered debris near Shanksville. Well, you don't get to make those demands. If we applied them to the Truthers, they'd be silent forever. To wit: Show us your hypothesis. Show me that you aren't Paul Doherty. Show me that you actually believe the crazy things you're typing on the Internet. Can't do it, can you?
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alienentity
Illuminator
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'NCSTAR 1-9 Vol 2,
'Once simulation of the global collapse of WTC 7 was underway, there was a great increase in the uncertainty in the progression of the collapse sequence, due to the random nature of the interaction, break up, disintegration, and falling of the debris. the uncertainties deriving from these random processes increasingly influenced the deterministic physics-based collapse process, and the details of the progression of the horizontal failure and final global collapse were increasingly less precise.'
'Once simulation of the global collapse of WTC 7 was underway, there was a great increase in the uncertainty in the progression of the collapse sequence, due to the random nature of the interaction, break up, disintegration, and falling of the debris. the uncertainties deriving from these random processes increasingly influenced the deterministic physics-based collapse process, and the details of the progression of the horizontal failure and final global collapse were increasingly less precise.'
alienentity
Illuminator
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Uhm, that question was just answered.
Ironically, if the NIST had just faked it, they would've been able to superficially mimic the actual collapse. Truthers don't seem to get irony..
RedIbis
Philosopher
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More like an opinion was offered.
TheRedWorm
I AM the Red Worm!
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What does it matter?
Edx
Philosopher
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I just watched a video from a truther claiming they were totally different but in reality only a small part of it was different, I don't know why you claim it looks "nothing" like it.
As alien said why, if it was fake, did they not make it look like just like the collapse? Again we have to believe in incompetent conspiracists
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ConspiRaider
Writer of Nothingnesses
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Very nice post, R. Mackey.
I remember poring through the NIST report and somewhere in there was mentioned that WTC-1 almost didn't collapse; that a non-collapse was plausible because of the position of the jet strike and the fact that it was struck much higher than WTC-2. For WTC-2, the equivalent of a 30-story building had to remain intact above the point of that strike. WTC-1 was about half that, if I recall.
Just that very very simple fact - that WTC-2 was struck later, but fell first - is an enormous blow to any fantasy of a pre-planned, non-aircraft-causation for collapse.
I used to work at Beaudry Center in downtown LA, and that is a 30-story building. You look up at that thing from bottom to top and actually can be amazed that a similar structure managed to remain aloft as long as it did above the point of impact on WTC-2.
I remember poring through the NIST report and somewhere in there was mentioned that WTC-1 almost didn't collapse; that a non-collapse was plausible because of the position of the jet strike and the fact that it was struck much higher than WTC-2. For WTC-2, the equivalent of a 30-story building had to remain intact above the point of that strike. WTC-1 was about half that, if I recall.
Just that very very simple fact - that WTC-2 was struck later, but fell first - is an enormous blow to any fantasy of a pre-planned, non-aircraft-causation for collapse.
I used to work at Beaudry Center in downtown LA, and that is a 30-story building. You look up at that thing from bottom to top and actually can be amazed that a similar structure managed to remain aloft as long as it did above the point of impact on WTC-2.
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DGM
Skeptic not Atheist
Because NIST did not model elements of the exterior face. I thought you knew this?
Actually NIST stated that under the minimum impact damage case they studied (treat it as a one-sigma lower bound on damage), the fires would have been expected to burn out and leave the structure standing. Under best-guess and higher damage cases, they predict collapse.
This, of course, assumes those fires didn't continue on higher floors and eventually trigger a minor collapse, one whose kinetics could have finally overcome the remaining strength on the impact floors.
Also, note that NIST is the only serious study that led to this conclusion. As I've noted many times, NIST's is the most optimistic study around. All of the other investigations disagree and think collapse was practically certain, even with less or (speaking to Purdue in particular) with no impact structural damage.
Obviously anything can happen in a crash, and if you tried it enough times eventually you would get a case that didn't collapse, but there's no question that the crash + fire led to the collapse, and that it would be expected to do so. Scientific consensus on these two points is total.
rwguinn
Penultimate Amazing
Modeling non-structural elements is, primarily, a waste of time and effort. You simply include the mass effects of non-structural elements, and concentrate your modeling efforts on the important parts.Mackey didn't mention that, any more information on this any why they didn't? I'm sure thats in the report but I'm busy and not a truther claiming its all fake
ConspiRaider
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Ten-roger, Mack. You wish to living hell it had gone that way - managing to remain standing, for at least two reasons:
1. Many many lives would have been saved.
2. All of us - including the truthers - would have seen an actual controlled demolition bring down the Tower. As deeply damaged as WTC-1 was, I doubt there'd have been any choice other than a CD. Had it somehow withstood the jet strike.
ElMondoHummus
0.25 short of being half-witted
Small addition (that Ryan already knows about, so he can sleep through this post
): University of Edinburgh researcher A.S. Usmani and some colleagues also believe this. Their computer modelings were run without taking into account jet impact damage, and they still managed to demonstrate a collapse just on thermal effects alone. In fact, the only "assumption" made was the failure of the fire suppressive system to either control the fires or even function at all. I also saw a reference to an Arup spokesperson coming out and saying much the same thing (although the close ties between Arup and U of Edinburgh's engineering school would of course lead them to state the same things; Architect can detail what those ties are if he feels like it).
I'm guessing that, given the emphasis on thermal effects with truss SFRM intact, that James Quintiere would also hold this opinion. I do admit, though, that this is just a guess.
ElMondoHummus
0.25 short of being half-witted
I need to read the NIST report segments on egress/evacuation, but: I think there were some sets of victims in that building who simply had no way to get out given the fires, and were also being overcome by the smoke/combustion gasses. So while your wish would've indeed led to more victims surviving, I fear that there still would've been a death count above and beyond the ones directly from the impacts, and also caught directly in the fires.
The part that chills me is the fact that there were a number of people who jumped; had the tower not collapsed, how many would've chosen that path? I can't tell. And I don't really dwell on that, since the actual tragedy was bad enough to encourage me not to think of other ways it could've been tragic.
Of course, anyone knowing more about the egress/evacuations can correct me on that.
ConspiRaider
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Yeahp. We're parallel-thinking on this, ElMondo, because it was the folks who went up top I was thinking about too, initially. I haven't looked at the figures awhile either on the estimate of those others who probably survived the impact and fires - but were trapped somewhere in the building just prior to collapse; stairwells, elevators, damaged rooms or offices without exit, others knocked unconscious and so forth.
Dave Rogers
Bandaged ice that stampedes inexpensively through
No, the question was answered very clearly. It's not Mackey's problem that you don't understand the answer.
Dave