BYU Professor: Explosives Used To Bring Down WTC

[Donnie B.]

Sorry I'm jumping in here so late, but...

There's one thing about this particular CT that totally baffles me.

There is indisputable visual evidence (indisputable to me, at least) that both WTC1 and 2 collapses began on the floors that were damaged by the aircraft impacts (plus or minus a few floors).

So how is this possible in a "controlled demolition" scenario?

Possibility 1: the towers were "mined" on the impact floors only. But for this to be true, the perpetrators would have to know in advance precisely where the planes would hit the building; furthermore, the explosives would have to NOT go off on impact, but rather be entirely undamaged (along with their wiring) so that they could be detonated nearly (or over) an hour later. [I assume here that there were no demolition engineers clambering around the damage area AFTER the impacts, setting and wiring up the charges on the burning floors!]

Possibility 2: the towers were "mined" throughout, from (say) floor 50 up. Then the planes hit the towers without setting off these charges, and someone figured out which floor to blow when the time came.

Possibility 3: As above, but only every fifth or tenth floor was wired, and the closest floor was selected.

Leaving aside the difficulty of getting those charges in place in advance without anyone noticing, of maintaining the integrity of the demolition charges and wiring through a ruttin' airplane impact and fire, and of coming up with an even remotely plausible motive for such actions...

How is any of the three possibilities feasible?

And why, if this were true, would the perpetrators not set off the charges upon impact? Why wait an hour? The calamity would have been far greater if the buildings had come down immediately rather than standing long enough for many occupants to escape.

The whole scenario just seems insane to me...

[twinstead]

Sorry
The whole scenario just seems insane to me...

LOL. Welcome to the club

[Peter B]

Okay Turbonium, I see your point, and I'm sorry for going off at a bit of a tangent. Nevertheless, there are a couple of points relevant to your statement.

Firstly, as Gillianren said, Romero never says how much explosives would constitute a "relatively small amount." Any statements which are based on this must necessarily be purely speculative.

Secondly, any such theory needs to explain how the explosives were placed, how they came to be placed in the right location, and how they survived the plane impact.

[Faultline]

Okay Turbonium, I see your point, and I'm sorry for going off at a bit of a tangent. Nevertheless, there are a couple of points relevant to your statement.

Firstly, as Gillianren said, Romero never says how much explosives would constitute a "relatively small amount." Any statements which are based on this must necessarily be purely speculative.

Secondly, any such theory needs to explain how the explosives were placed, how they came to be placed in the right location, and how they survived the plane impact.

And if anyone wants an explanation of the "secondary explosions" that were heard by firefighters and such, tell them that many things can explode in a burning building, especially one as complex as the WTC.

Air conditioner units, sprinkler system tanks, fire extinguishers, methamphetamine labs (whoops! none of those in there], anything pressurized could explode.

[JayUtah]

But there is no reason to suppose the noises they heard must have been explosions. A steel beam or column snapping sounds very much like an explosion, and it is not within the normal person's experience to have heard one snap.

Yes, many of the eyewitnesses say they heard "bombs" or "we knew it was a bomb." But evaluating eyewitness testimony involves separating observation from interpretation. The eyewitnesses themselves are not always good at doing that because it is human nature to try to categorize an observation on the spot. A skilled interviewer can get past what the eyewitness thought caused the observation and arrive at what the eyewitness actually saw or heard.

None of the eyewitnesses actually saw or heard a bomb -- that is, made an observation that clearly distinguished the cause as an explosive device or substance. They heard loud, concussive noises. The myriad possible sources of such noises in the WTC scenario generally lie outside the normal person's experience, so a lay person won't necessarily be able to distinguish a pressure wave from the release of mechanical strain energy from a C-4 explosion.

Firsthand witnesses are obviously the authority on what they saw or heard, but they are not necessarily authorities on what caused the thing they saw or heard.

[akirabakabaka]

Please re-read the discussion that deals with localized temperatures. You seem to believe that there were vast portions of one or more floors that were consistently at very high temperatures. That is not the claim, and that is not what is necessary to fail the structure.

Is that discussion part of this thread? That's exactly what I was asking, what is the explanation for the apparently contained yet intense fires?

The no-melted-steel group has largely ignored this report, which found evidence of liquified steel.

Hardly. The conspiracy crowd staunchly argued that no evidence whatsoever of melted steel in any form had been found, thus the structure couldn't have softened and deformed as believed.

I'm not sure where else you discuss these things, but I don't beleive that claim was ever made on this thread. (EDIT: I mean by the conspiracists, this has only been claimed by the debunkers)

Then one of my colleagues -- not the conspiracists -- came up with this citation. Now all the conspiracists use it to try to prove there was additional explosives or fuel other than what had been accounted for in the accident. No matter what the evidence, the conspiracists argue for some deliberate conspiracy in all cases!

The "no-melted-steel" group, so-called, disputes the claim that significant amounts of melted or molten steel were discovered in the WTC 1 and 2 basements, evidence they say of large-scale use of something like thermite. This has little to do with eutectic mixtures.

The argument has been skewed between the molten metal, which was witnessed as "steel" by many people supposedly, yet none of them had any way to know if it was steel or even just alluminum. But the WPI claims about the WTC7 steel still supports the argument that steel melted somewhere at some time on 9-11, which has been under debate:

C.3 Summary for Sample 1: "Heating of the steel into a hot corrosive environment approaching 1,000 °C (1,800 °F) results in the formation of a eutectic mixture of iron, oxygen, and sulfur that liquefied the steel."

...since most of the evidence was destroyed, they have to verify their models using visual evidence.

Why is this improper? Why is "visual evidence" not empirical?

How many investigations have you personally directed?

I appreciate your zealous defense, but you've been tending to be confrontational about claims I've never made. I made the simple statement that they had to verify their models with the visual evidence, which you have previously agreed with. Nobody ever said it was "improper" or "not empirical", you're just being paranoid.

6.6.3 explains how these global reference models weren't even used for the impact simulations. "the model had to “fit” on a state-of-the-art computer cluster and to run within weeks rather than months." (p.92) -- why such a limited time restraint after spending years on this investigation?

Because the computers themselves don't stay running for more than two weeks or so without something going wrong. If the computer breaks down during the run, most of the data are lost and the model must be re-run from the beginning. I design, build, and sell supercomputers for a living, which are then used by my customers, with my assistance, to solve these certain kinds of engineering problems. You're talking about my bread and butter here.

Whoa, just to interject, but what kind of supercomputer can only run for two weeks and then loses all of its data?

A computer does not exist in the unclassified world that can contain an ANSYS model of the entire WTC structure at the resolution necessary to provide as detailed a model for the entire building as was done for the affected floors. And my consultation with the ANSYS people -- with whom I do business -- has suggested that there are additional software limitations.

Then you are correct, these are state-of-the-art models, but I was also correct that they are inaccurate and incomplete.

From what I can tell they only ran the impact simulation a single time.

Read again.

Done, it still looks like they ran the impact simulation a single time.

"The combined tower and aircraft model of more than two million elements, at time steps of just under a microsecond, took approximately two weeks of computer time" (p.92)

Why do you believe that run did not include multiple parameter sets?

Where is this stated in the report?

The fires all took place in the same area near the point of impact.

No, they didn't.

Between floors 92 through 100 on WTC1 and floors 77 through 85 on WTC2. This isn't near the impact?

Because there's pictures of a woman standing near this area where supposedly there are 1000C fires raging.

No. Those occurred at a different time and place. The report is fairly clear.

So the fires lasted 15-20 minutes then the building slowly collapsed on itself as it cooled down?

I'm surprised about how confident everyone is in these simulations as undeniable proof of that claim.

I'm surprised at your continued willingness to cast aspersion on something you clearly know little about. You ride in cars and airplanes whose designs were validated as safe using nothing but these computer models. You already trust your life to these algorithms, which have been tested and refined over 25 years; you just don't realize it.

You are simply desperate to disbelieve the models. Why?

I've been explaining why, they are incomplete. But really, nothing but computer models? They don't ever stress test materials? Ever?

It appears that it was decided how the collapse occurred, and the investigators set out to prove that scenario.

No, they set out to disprove it. That's basic scientific method. My job frequently involves forensic and failure-analysis engineering. I do this for a living. What investigations have you personally directed? Why is your intuition on how to study something to be considered more authoritative and correct than those, including me, who have been trained to do this?

This is what irritates me about conspiracy theorists. They ignorantly presume that what little they happen to know about some subject is as much as anyone knows, even qualified experts.

I know it's frustrating when everyone else isn't as smart and experienced as you, but thats why it's an open discussion. I'll respond to some more when I've got a chance, gotta run to class

[dinAlt]

Okay, how about this? What would convince you?

I am neither here to prove nor disprove the hypothesis of controlled demolition. This would be outside the bounds of my personal expertise and resources. My primary interest is in raising the quality of debate. Most proponents of both sides of this debate do not appear to comprehend the arguments of their opponents, nor do they appear to understand the strengths and weaknesses of their own arguments, as they merely take the word of others or go with their gut feelings. To be an effective debater, one must understand the arguments of his opponent at least as well as his own, if not better. The claim of your opponent may be wrong, but what good is it to hold the belief he is wrong, without understanding why?

Let's start with a short lesson in logic and reasoning. An argument consists of a number of premises, which are assumed to be true, for the sake of the argument. From these premises, logical inferences are drawn to reach a conclusion. The easiest way to invalidate an argument is to demonstrate one or more of the inferences is not logically valid. If a logical fallacy has been committed, then there is no need to examine the premises. If the inferences are sound, then one must falsify one or more of the premises.

Falsifiability is an important concept to the philosophy of science. For a proposition to be falsifiable, it must be possible, at least in principle, for an observation to be made, which would show the proposition to be false. This is directly applicable to invalidating the premises of an argument, where a premise becomes a proposition to be falsified. If a premise is falsifiable, then it is within the domain of scientific inquiry.

The formal method of the falsification of theories is through Modus Tollens. Given theory T, which implies observation O:
T -> O
If observation O is not made,
~O
then by Modus Tollens, the theory has been falsified.
~T

To answer your question:

1. Argument: Asymmetric fire damage to the WTC towers could not have resulted in symmetric collapse, therefore the collapse must have had an origin other than the fires.

The inference is logically valid, therefore we can not invalidate it through fallacy. We must next consider the premise, which is commonly dismissed via the fallacious argument: The WTC towers did experience symmetric collapse, therefore asymmetric fire damage must have caused the symmetric collapse. This is an example of 'begging the question' or circular reasoning, as it presupposes the fires caused the symmetric collapse.

If we consider the premise to be a proposition, is it a falsifiable? This theory is falsifiable, as conceptually it should be possible, by means of computer modeling, to demonstrate symmetric collapse caused by asymmetric damage of the type believed to have occurred. To date, this analysis has not been performed. If such an analysis were to be performed in a scientific, peer reviewed study, and it concludes the buildings should have experience symmetric collapse from the fires, I will be convinced.

2. The hypothesis of controlled demolition implies the observation of residue from the explosives. Through forensic analysis, it should be possible to establish the presence or absence of such residue. I don't believe such a analysis has been undertaken, as it has been assumed the buildings were destroyed by the fires. If it can be conclusively shown there was no residue, then I will convinced.

----
I'm not a real conspiracy theorist, I just play one on TV.

[akirabakabaka]

1. Argument: Asymmetric fire damage to the WTC towers could not have resulted in symmetric collapse, therefore the collapse must have had an origin other than the fires.

The inference is logically valid, therefore we can not invalidate it through fallacy.

Wasn't this the question; whether or not this is a logical argument? I think dougreed rebutted it nicely.

We must next consider the premise, which is commonly dismissed via the fallacious argument: The WTC towers did experience symmetric collapse, therefore asymmetric fire damage must have caused the symmetric collapse. This is an example of 'begging the question' or circular reasoning, as it presupposes the fires caused the symmetric collapse.

I think this is what JayUtah has been addressing from the 2005 NIST report; the fires initiated a quick progressive collapse. In WTC1 apparently the fire was concentrated on the center core beams, not sure about WTC2. From the videos, WTC2 (the south tower) was almost missed by the plane which went through the corner; the collapse of WTC2 is mostly to one side initially, the other side falls a bit slower. I'm still going through the 2005 NIST report to see how they handled all of this in the simulations.

2. The hypothesis of controlled demolition implies the observation of residue from the explosives. Through forensic analysis, it should be possible to establish the presence or absence of such residue. I don't believe such a analysis has been undertaken, as it has been assumed the buildings were destroyed by the fires. If it can be conclusively shown there was no residue, then I will convinced.

I've discussed this also, only the impact/fire scenario was really investigated. There might be some clues from the WPI metallurgical examinations, but most of the evidence was destroyed. I'm starting to lean toward the conclusion that the WPI evidence does not support explosive devices, and that it might support the official explanation instead (although their data has not been integrated into the official explanation AFAIK)

[akirabakabaka]

Sorry I'm jumping in here so late, but...

There's one thing about this particular CT that totally baffles me.

There is indisputable visual evidence (indisputable to me, at least) that both WTC1 and 2 collapses began on the floors that were damaged by the aircraft impacts (plus or minus a few floors).

That's really the whole difference to many people's views of how the towers collapsed. Some people see an orderly planned explosion, others see nothing but chaos.

[Cl1mh4224rd]

I've been explaining why, they are incomplete. But really, nothing but computer models? They don't ever stress test materials? Ever?

Uhh... You can't be serious. I'm sure the properties of steel beams and whatnot were already well-known. Or are you suggesting that they re-test materials for each incident?

[PhantomWolf]

Whoa, just to interject, but what kind of supercomputer can only run for two weeks and then loses all of its data?

One that catches fire, ah Jay. However being serious, few programmers write their program to continuously write the data of a continuing program to the HDD, especially when you may be using several million variables, the download and upload time just makes the act totally unfesible. Instead you keep the data in memory and only write the results to the HDD after the system has finished. Of course this introduces the risk of losing all that data should the computer over heat have a power supply failure, or simply crash, which even super cmputers do, in fact they are prbably more likely to do it because of the software they run, and the conditions they run under.

[PhantomWolf]

Between floors 92 through 100 on WTC1 and floors 77 through 85 on WTC2. This isn't near the impact?

I think that what Jay was getting at was that the fuel etc was moving at the time of impact and hence continued into the building sweeping withit any combustable materials. As such there was nothing left to burn at the site of the impact itself and so wasn't any major fire there, the fires were where there was a fuel load of combustables, deeper into the cetre of the Tower.

So the fires lasted 15-20 minutes then the building slowly collapsed on itself as it cooled down?

Actually this phase can often be more dangerous that the heating phase. Metal that has been heated will expand and then softened and then deform. Then once the heat load is removed and it starts to cool it regains its strength and contracts, but because it has deformed it no longer fits and so it applies forces to the rest of the structure, shearing bolts and pulling columns out of alignment.

I've been explaining why, they are incomplete. But really, nothing but computer models? They don't ever stress test materials? Ever?

I don't think you really understand the FEA models. All materials on the planet can be represented with a bunch of numbers. They have a number to represent their heat transfer, their melting point, their tensile strength. These things are determined empirically, by bending them, heating them, melting them, shattering them, etc, but once you have them you don't need to do it again. If I have a specific piece of aluminium and I want to know the amount of heat it will tranfer at 25°C, I don't have to do that empirically, I can look it up on a table. If I want to learn the stress a piece of steel beam will take, I don't have to test it emprically, I can look it up. These numbers are what the FEA modelling deal with. If a sheet of aluminim has been tested previously and has a rating that tells me that it can resist a certain amount of flexing before it forms cracks and fractures, I can model an aircraft wing made from that metal and test it to destruction, the model producing an extremely accurate result. I don't have to make the wing and get the Samoan Rubgy team to jump up and down on it for the next two weeks to stress test it. The physics and the numbers are well know and that allows the models to operate extremely accurately. Even the collapse of the towers themselves could in theory be modelled using a computer, the trouble is that you'd need one capable of dealing with trillions of variables to represent every particle in the Tower, and as of yet we just don't have a machine that can hold that sort of data. The software to do it however isn't overly hard.

[turbonium]

I wrote...

I meant to emphasize that FEA is at best a method of analysis for which even at it's optimal employment still can only achieve approximate, not definitive, results and conclusions.

And you say this from your vast experience in finite-element analysis and engineering test and development?

You have no clue what you're talking about

Below are links and excerpts which you might want to look at....

"FEA is Approximate. The first issue to understand in Finite Element Analysis is that it is fundamentally an approximation. The underlying mathematical model may be an approximation of the real physical system (for example, the Euler-Bernoulli beam ignoring shear deformation). .....The result of an analysis contains the accumulated errors due to all of the contributing approximations"

http://www3.sympatico.ca/peter_budge...ng_issues.html


"FEA is widely accepted in almost all engineering disciplines. The technique is based on the premise that an approximate solution to any complex engineering problem can be reached by subdividing the structure/component into smaller more manageable (finite) elements."

http://www.hera.org.nz/PDF%20Files/FEA%20Brochure.PDF

I said it from looking at these and other sources of information on FEA.

[dinAlt]

For "no evidence," let's start with no evidence that anyone ever acquired enough explosives to do a controlled demolition. (I'm not expert, but it would take a lot, if a jetliner full of fuel crashing into the building wouldn't bring it down.) Let's continue with no evidence that anyone ever saw the preparations, despite how many people were in and out of all three buildings all the time. How 'bout no evidence that it would even require explosives to bring the building down?

How much explosives would it take? That's an interesting question and is well within the bounds of what can be determined with a little googling, at least for a first order approximation.

Field Manual: Explosives and Demolitions by U.S. Army, 1971

b. FORMULAS FOR PLASTIC OR SHEET EXPLOSIVE CHARGES. When using plastic explosives (M5A1 or M112) charges or sheet explosive (M118 or M186) charges, which may be cut to fit the target and attached to the surface of the target with little or no air gap, the following formulas, based upon optimum charge configuration and optimum contact with the target, may be used. The following charge calculations are based upon the dimensions of the target, and with some practice these charges may be calculated, prepared, and placed in less time than the charges calculated by the formulas listed above. These charges may also be prepared in advance for transportation to the site by wrapping them in aluminum foil or heavy paper. The wrapper should be removed when the charge is attached to the target. When preparing these charges the explosive should be cut to the proper dimensions, not molded, as molding the explosive will reduce its density thereby decreasing its effectiveness. (1) RIBBON CHARGE METHOD. The charge, if properly calculated and placed, cuts steel with considerably less explosive than standard charges. It is effective on non circular steel targets up to 3 inches thick (fig 3-7). Although this charge is based upon the use of C4 plastic explosive, sheet explosive may be used provided the 1/4- by 3 by 12-inch sheets of flexible explosive are used intact and complete charges are at least 1/2 inch thick. (a) CALCULATION. The effectiveness of the explosive depends upon the width and thickness of the explosive. The thickness of the charge is one half the thickness of the steel. The width of the charge is three times the thickness of the charge. The length of the charge should be equal to the length of the desired cut.

The smaller and more numerous core columns near the middle of the tower are estimated to have been 36 x 12 inches around the perimeter and about 2 inches thick; the corners had larger columns. Applying the formula from the above reference, this would suggest a strip of C4 about 1 inch thick, 3 inches wide, and 96 inches long, for a total volume of 288 inches^3 or 4700 cubic centimeters.

The M112 demolition charge (C4) has the dimensions of 1/4 * 3 * 12 = 9 inches ^3 (147 cc) and a weight of .5 lbs (227 g). This gives a density of 1.55 g/cm^3. This would give our charge a mass of: 4700 cm^3 * 1.55 g/cm^3 = 7.3 kg (16 lbs). For simplicity sake (and lack of blueprints), we will assume all 47 columns are the same. This gives a total mass of 340 kg (750 lbs) of C4 to cut all the columns on a single floor. If we were to set charges on every 4th floor from floor 50 to the top (14 floors), we would need 4.7e3 kg of explosives.

Having charges on every fourth floor from floor 50 to the top, to ensure we could cleanly cut the core near the point of impact, we would need to set 47 * 14 = 658 charges. As the charges could be prepared ahead of time, I will assume it would take about 10 minutes to set each charge, for a total of about 110 man hours to setup the demolition. A four man team could complete this task in about 28 hours.

When could have this taken place? Here is a report by “Scott Forbes,” an IT worker, in the south tower.

http://www.serendipity.li/wot/forbes01.htm

On the weekend of 9/8,9/9 there was a 'power down' condition in WTC tower 2, the south tower. This power down condition meant there was no electrical
supply for approx 36hrs from floor 50 up. I am aware of this situation since
I work in IT and had to work with many others that weekend to ensure that
all systems were cleanly shutdown beforehand ... and then brought back up
afterwards. The reason given by the WTC for the power down was that cabling
in the tower was being upgraded ... Of course without power there were no
security cameras, no security locks on doors and many, many 'engineers'
coming in and out of the tower. I was at home on the morning of 9/11 on the
shore of Jersey City, right opposite the Towers, and watching events unfold
I was convinced immediately that something was happening related to the
weekend work ...

This would certainly afford the opportunity for a four man team to plant the 4700 kg of explosives. I don't trust the reliability of this statement, but with a real investigation, it could be verified or discounted. I would also think this would leave a tremendous amount of explosive residue from the RDX in the C4, which could be verified by a forensics lab.
----
I'm not a real conspiracy theorist, I just play one on TV.

[turbonium]

Yes. You made up a fanciful story that speaks to a supposed motive that you already believe for other reasons. You have no evidence that this actually happened. There are innumerable posssibilities, including the one that an army of invisible elves toppled the towers. Why haven't you considered that "possible" scenario too?

That's nonsense. Obviously I don't have evidence, nor did I claim or even imply that this actually happened. It was written as a theoretical possibility. The scenario I described could indeed have taken place, under the guidelines NIST set up for the steel recovery task, and that is the reason I put it forth - to illustrate and underscore my point. Why is it such an impossible stretch for you to consider that the core columns from the floors "relevant to the collapse" may have actually never reached temperatures high enough to initiate the collapses? No physical evidence was found to support your belief and NIST's conclusions.

NIST, as with all such investigating agencies, knew it would not be possible or practical to recover and identify a significant percentage of WTC steel, nor necessarily possible to locate and recover the steel that had been at the hottest points in the structure. Therefore they knew going into the investigation that some sort of CSD model would be the primary investigative tool. With that in mind, you don't have to recover specific elements of steel, only sufficiently diverse pieces to validate the model. That is a broader set of criteria that have to be met, and therefore one more likely to be met from convenience samples.

You seem to argue that this is somehow a scientific foul, or that it introduced too many degrees of freedom for the model to be predictive. That is simply ignorant; that's not how FEA models work.

You have missed my point - NIST never considered steel unaffected by fire and/or plane impact from the affected floors to be relevant to their investigation. As I said, that is because this steel does not and would not support the NIST report in several areas, among them: working hypothesis, introductory abstract, description of initial collapses (such as WTC 1 and 2 Structural Response to Elevated Temperatures http://wtc.nist.gov/oct05NCSTAR1-6index.htm (pgs.243 and 260) and in their summary conclusion.

It is usually not possible to recover all the physical evidence, and often less revealing in the long run. Let's say you find a bent girder in a pile of rubble. How do you know that girder was bent in the chain of events that led to the collapse, or was instead bent after the collapse had already begun and was thus unstoppable?

Your example does not hold for comparison with the WTC steel sampling and working hypothesis. You are implying that there is a danger of actually recovering too much physical evidence, because it will often lead to confusion and flaw an investigation. But remember, the WTC steel was identified as to the area it was located within the structure. As NIST stated, much of the steel was indeed able to be identified during recovery. So if, for example, Core Columns 1000 through 1025 were able to be identified as coming from Floor 96 of WTC 1, they could (and should) have been recovered for analysis. Metallurgical tests could then be conducted for exposure to fire. The results may show exposure to temperatures above 250C for almost every core column. That data can be input for FEA model analysis. But, if the results show exposure to temperatures was in fact below 250C for every core column, that data must also be included in the FEA models. And those numbers would throw the proverbial wrench into the works.......

You're saying the investigation was done wrong because it relied on modeling rather than inspection of recovered steel, and you're trying to say that NIST looked in the wrong place for the samples they did recover. But your objection is simply based on your personal notion of how to conduct a forensic engineering analysis and investigation.

No, I said it was wrong to prefer to rely on modeling rather than analysis of physical evidence, when the option existed to recover much more of the steel relevant to the collapses. As I said earlier, that includes all the steel from these floors, whatever condition it is in. NIST excluded any steel from these floors unless they had impact damage and / or exposure to fire.

Are you contending that none the core column steel from the affected floors (92 through 100 on WTC 1 and 77 through 85 on WTC 2) is not relevant to the investigation unless it has damage from impact and/or exposure to fire?

Now you're trying to apply criterion B to objective A....
Part of NIST's mandate was to investigate the structural response of the building to the impacts alone, irrespective of the fire.

One of NIST's main objectives was also to show how fire and plane impact were the causes of initial collapse in both towers. Their criteria were also limited to locating and analyzing steel samples which had evidence of fire and/or plane impact. Your "criterion B" is your ID for what I described as "all the steel from these floors". But "criterion B" did not exist in the NIST steel "shopping list".

[ZappBrannigan]

What a long, strange trip it's been. I just feel the need to jump in with a couple of questions of my own, one general, one to the CTers.

1. I get the impression that the CT point of view is that the planes were supposed to hit the towers, and then an hour later the conspirators were to blow them up. I have not read a huge amount of material on the hijacker's motives (outside of the virgin obsession,) but I would assume, since they were flying at maximum speed, and hit "high," that they intended to knock the towers over with the impacts of the planes. That would cause far more damage, for one thing. Lots more city blocks taken out, and in an instant. Has anyone ever seen any sort of "mind of the terrorist" paper that dissected their intent?

2. For the CTers: If the conspirators were going to blow up the buildings, why did they need planes at all? A few guys with a van almost(?) blew up a tower back in the early '90's. Why not just set it up to look like a terrorist group finished the job? Immediate impact. Far greater catastrophe. Hmmm. Maybe they wanted to make sure the whole world was watching when it happened, thus the planes hit first to ensure a global audience for the collapse. Okay, blow one tower. Wait 40 minutes blow the other. You still don't need any planes. Why the needless complication? Is Jerry Bruckheimer the real brains behind this Rube Goldberg-esque plan? I don't like him. I'm willing to believe it.

Just had to throw those out there. And I really am interested in the answers.

[turbonium]

Firstly, as Gillianren said, Romero never says how much explosives would constitute a "relatively small amount." Any statements which are based on this must necessarily be purely speculative.

Secondly, any such theory needs to explain how the explosives were placed, how they came to be placed in the right location, and how they survived the plane impact.

Of course, the actual amount of explosives was not detailed by Romero. That would depend on what type or types of explosives were used, where they were placed, etc. I only pointed it out as a general rebuttal to the claim that an "enormous" amount would be needed.

The other details you mention require a new, comprehensive investigation into many elements the official investigation either ignored or did not proceed with beyond a brief skimming over. One can speculate on these points within a theory, but proof for it will only come from digging into the muck and clearing out many obfuscations which have grossly impaired the public release of relevant information. The question also arises over whether enough evidence still exists to provide support for investigating possible use of explosives. For example, was any of the molten metal recovered for analysis? Not to my knowledge.

[turbonium]

If the conspirators were going to blow up the buildings, why did they need planes at all? A few guys with a van almost(?) blew up a tower back in the early '90's. Why not just set it up to look like a terrorist group finished the job? Immediate impact. Far greater catastrophe. Hmmm. Maybe they wanted to make sure the whole world was watching when it happened, thus the planes hit first to ensure a global audience for the collapse. Okay, blow one tower. Wait 40 minutes blow the other. You still don't need any planes. Why the needless complication? Is Jerry Bruckheimer the real brains behind this Rube Goldberg-esque plan? I don't like him. I'm willing to believe it.

You have mentioned a reason I believe planes were used..."Maybe they wanted to make sure the whole world was watching when it happened, thus the planes hit first to ensure a global audience for the collapse."

But, although I agree you don't need to use planes to accomplish the goal of collapsing the buildings, they do have advantages over using vans with bombs in the basements, as in 1993. First, the 1993 bombing did not come anywhere near to collapsing the tower. They would need to explain how it could then be successful for both towers on 9/11, but not in 1993. Second, they could not use the excuse that "nobody could have ever predicted terrorists would do this", because it had indeed already been attempted. And since 1993, they implemented security measures to prevent a repeat of that event. Third, the pyrotechnic display of the airplane impact live on TV before tens of millions of people provided the ultimate "shock" to the emotions. A basement explosion would not be nearly as "spectacular" a display of savage destruction and mass murder.

[dinAlt]

Sure; it's easy. First, the WTC 7 collapse was not "symmetric". Second, there's no presumption in structural mechanics that assymmetric loading or localized failure must produce an "asymmetric" response in the structure.

You have to realize that homespun expectations and ad hoc analysis methods are not really going to arrive at a defensible conclusion, or even poke substantial holes in someone else's conclusion.

Thank you for addressing my question. Your posts are the most intelligent I have seen on this board and they have added considerable insight to my understanding on a number of issues.

You are correct in identifying the professor's analysis of the collapse as ad hoc. This is why I would like to see an analysis of the collapse made by qualified personnel. We had three building fall into their own footprint from non-uniform damage on the same day. I would like to be able to say, with confidence, this is what we should have expected. I currently have to admit that I don't know. We are dealing with a complex system, where intuition and common sense do not necessarily apply. Do you know if software currently exists to model this type of dynamic system? Confirming the observed behavior to be the expected behavior would add additional credibility to the official story.

Thanks.

[dinAlt]

I have been wondering, if it was a conspiracy, why did the "bombers" bring the buildings straight down? Wouldn't it have raised fewer eyebrows if they had just haphazardly knocked it over?

If we assume the premise of controlled demolition is true, which is a big if, then I would propose the following conjecture: The objective of the operation was to create a spectacle. The mere crashing of the planes into the towers, without collapse, would not be sufficiently dramatic to sell the war. To ensure the destruction of the towers, explosives were planted on core columns on a number of floors within the likely range of impact. While the goal was not specifically intended to cause symmetric collapse, this was the side effect of simultaneously severing the core columns.

Arguing against the controlled demolition hypothesis on the basis of lack of means or motive is pointless. We can argue about this all day long and not make any progress because such propositions are not falsifiable. I do find this type of speculation amusing, so please excuse my indulgence in this behavior, but don't read too much into it.

The purpose of my conspiratorial posts are merely to illustrate how pointless this type of discussion is. For any objection to the lack of means or motive, I can invent a coherent explanation, which is entirely unfalsifiable. Don't let conspiracy theorists drag you into this type of argument, as neither side will ever convince the other of anything. Try to stick to claims, which can be falsified.

If I may make one further observation: many members of this forum have no imagination and some have far too much. Try working towards a happy median.
---
I'm not a real conspiracy theorist, I just play one on TV.

[dinAlt]

Asymmetric fire damage to the WTC towers could not have resulted in symmetric collapse, therefore the collapse must have had an origin other than the fires.

The inference is logically valid, therefore we can not invalidate it through fallacy.

Wasn't this the question; whether or not this is a logical argument? I think dougreed rebutted it nicely.

I'm confused by this statement. This is the formal argument:
A: asymmetric fire damage
B: symmetric collapse

If A, then not B (A -> ~B)
B is true (B)
Therefore, A is false (~A)

The premises are disputable, but I don't believe the logic is. Did dougreed repeal Modus Tollens?

[Donnie B.]

That's really the whole difference to many people's views of how the towers collapsed. Some people see an orderly planned explosion, others see nothing but chaos.

I don't understand what you're trying to say here. For one thing, you're falsely excluding the middle (a chaotic collision/fire can certainly lead to structural failure that looks somewhat "orderly" -- though the resulting debris pile was anything but orderly).

What's more, your response doesn't really address the main point. Do you dispute that the WTC1 and 2 collapses began at or near the impact floors? If you deny this, I say you're ignoring the clear evidence in the films made that day.

On the other hand, if you accept the evidence and agree that the collapses began at the impact floors, you need to address the three possible scenarios for how the demolition was done. Do you seriously think any of them is feasible? Which one? If not, what alternative scenario do you propose?

[Faultline]

If the conspirators were going to blow up the buildings, why did they need planes at all? A few guys with a van almost(?) blew up a tower back in the early '90's. Why not just set it up to look like a terrorist group finished the job? Immediate impact. Far greater catastrophe. Hmmm. Maybe they wanted to make sure the whole world was watching when it happened, thus the planes hit first to ensure a global audience for the collapse. Okay, blow one tower. Wait 40 minutes blow the other. You still don't need any planes. Why the needless complication? Is Jerry Bruckheimer the real brains behind this Rube Goldberg-esque plan? I don't like him. I'm willing to believe it.

You have mentioned a reason I believe planes were used..."Maybe they wanted to make sure the whole world was watching when it happened, thus the planes hit first to ensure a global audience for the collapse."

But, although I agree you don't need to use planes to accomplish the goal of collapsing the buildings, they do have advantages over using vans with bombs in the basements, as in 1993. First, the 1993 bombing did not come anywhere near to collapsing the tower. They would need to explain how it could then be successful for both towers on 9/11, but not in 1993. Second, they could not use the excuse that "nobody could have ever predicted terrorists would do this", because it had indeed already been attempted. And since 1993, they implemented security measures to prevent a repeat of that event. Third, the pyrotechnic display of the airplane impact live on TV before tens of millions of people provided the ultimate "shock" to the emotions. A basement explosion would not be nearly as "spectacular" a display of savage destruction and mass murder.

Plus, its hard to find something else that packs the explosive and incendiary damage of 15,000 gallons of jet fuel as poorly guarded as our airliners were before 9/11.

[akirabakabaka]

I don't think you really understand the FEA models. All materials on the planet can be represented with a bunch of numbers. They have a number to represent their heat transfer, their melting point, their tensile strength. These things are determined empirically, by bending them, heating them, melting them, shattering them, etc, but once you have them you don't need to do it again.

Then why the Cardington fire tests? Why bother doing this sort of work at all if simulations are so much easier and all of the values already known? My company is forced to submit fully assembled products to be stress tested by heat, impact, vibration, etc. What's the point when we could just email our specs and have a computer do it for us? Again I think reliance on the simulations is overstated.

[gwiz]

To be brief, verification of the (computerised) design method.

[akirabakabaka]

I'm confused by this statement. This is the formal argument:
A: asymmetric fire damage
B: symmetric collapse

If A, then not B (A -> ~B)
B is true (B)
Therefore, A is false (~A)

The premises are disputable, but I don't believe the logic is. Did dougreed repeal Modus Tollens?

You're trying to make the case that asymmetric fire damage logically results in an asymmetric collapse, but others have shown this is probably not true, and that the WTC buildings had asymmetric collapses anyways. Your 'logical' relation between A and B is meaningless if the entire premise is not factual. The premise "If A, then not B" is factually wrong, even if logically consistent.

[akirabakabaka]

I don't understand what you're trying to say here. For one thing, you're falsely excluding the middle (a chaotic collision/fire can certainly lead to structural failure that looks somewhat "orderly" -- though the resulting debris pile was anything but orderly).

I was referring to the overall way people perceived it; either chaotic terrorism or orderly demolition. Even orderly demolitions aren't actually 'orderly', I think you're just nitpicking.

What's more, your response doesn't really address the main point. Do you dispute that the WTC1 and 2 collapses began at or near the impact floors? If you deny this, I say you're ignoring the clear evidence in the films made that day.

The collapses occurred at the core supports which were not visible whatsoever, so what clear video evidence do you claim supports the collapses beginning where you say?

I'd say that from the outside WTC2 appears to crumble starting at the lowest damaged floor, but I don't believe this is where the failure is said to have happened. WTC1 is inconclusive since the entire core collapses at once, seen by the drop of the communication tower, so it could have happened within a large range according to video.

Were the simulations detailed enough to pinpoint which beam, or even which floor, collapsed first?

[JayUtah]

Then why the Cardington fire tests?

To validate new models or refinements on the old models. If you read the Cardington papers, the whole point was to see whether the digital models for global structural and thermodynamics accurately predicted the outcomes.

Why bother doing this sort of work at all if simulations are so much easier and all of the values already known?

Because the simulation method has to be validated at some point. That doesn't mean you have to revalidate the method every time you use it, but at some point you have to show that it will preduct an empirically determined result at the global perspective. Then you can use it in place of empirical tests that are too costly or too impractical.

FEA breaks up a problem into generic, manageable elements. The boundary conditions between the elements are computed according to straightforward and context-agnostic constitutive relationships. The sum of the local effects produces a global effect that gradually acquires the global properties of the problem as one's perspective becomes more global.

In the example I used previously, the heat transfer and thermodynamics problem of the asymmetrically-heated beam is built up from the interactions between those small, cubic-millimeter elements. Each element interacts only with its neighbors in a way that is relatively easy to determine. Any two adjacent cubic millimeters will react to each other whether they're part of a beam or a frying pan or a jet turbine. But of course the effect of element A on element B depends on the effect of element B on A, so we have to solve that boundary condition in a simultaneous equation. As this propagates through the problem, you end up with a linear (or sometimes non-linear) system that can have tens of millions of unknowns. Solving this gargantuan linear system is what takes two weeks. The geometry of the problem is expressed in the distribution of coefficients in the matrix.

Any time you build up a global solution from small, constituent solutions, you run the risk of nonlinear behavior having a disproportionate effect on the global outcome. That is, if your individual constitutive relationships are not properly specified, that error might create a divergent effect. It may converge too, but you want to catch any divergent errors. The only way to do that is to do at least one global validation. But if the global validation succeeds, you don't have to do it every single time.

Let's say you go out and buy one of those new-fangled laser levels. You slap it on the wall and tweak it until the bubble looks right to you. But you know that any error in your reading will compound at the end of the line. Sure, the line is 60 inches off the ground where you're standing, but (assuming level ground) it might be 60.125 inches forty feet along the wall to your right because the longer the line extends, the more the error will compound. So you walk over there and take a measurement. If you get 60.03 inches, you can consider the level "good enough". If it reads 59.33 inches, then either the level is broken (but let's assume it isn't), or you need to take greater care reading that bubble.

Once you've calibrated your bubble-reading skills, you don't have to double-check it every time you use the level. And that means you can now use it confidently in contexts where it might not be possible to double-check it.

My company is forced to submit fully assembled products to be stress tested by heat, impact, vibration, etc.

What do you make?

Imagine having to submit a fully-equipped $100 million airliner for destructive testing in order to understand the behavior of the product. Not all testing is created equal. If you make cell phones, it doesn't cost that much to run off ten items to see if they will still work after you boil them or run over them with your car.

There is a difference between qualification testing and testing that is used to investigate design. My customers build $300 million satellites. Every satellite is still qualified by baking it in a vacuum chamber and shaking it. The one thing a computer model can't determine is whether you built each individual unit properly. You can have a remarkable and robust design, but if the production floor fouled up then you want to know about it before you bolt it to the top of a rocket and shoot it out tens of thousands of miles into space.

That doesn't mean that the designers who drew up the plans used those same methods to see whether their designs would work. They didn't put together a million-dollar prototype and then shake it to pieces to see whether their design could accept acoustic loading, then throw it out on the scrap heap and go to work on the next prototype with lessons learned. No, they ran all that stuff in the computer and adjusted their designs accordingly. That process doesn't work unless the models actually do predict what would happen in real life.

Now Boeing used to do this for airliners with very expensive and time-consuming scale models in wind-tunnels. They don't do that anymore. It costs too much money and takes too much time to build those models, and they really don't learn as much as they want to by streaming smoke around them in real-live wind tunnels.

What's the point when we could just email our specs and have a computer do it for us?

Because understanding the behavior of a design and acceptance or qualification for statutory regulation are not the same thing. Acceptance testing simply wants to answer the question, "Will this example of the product withstand these adverse effects and inputs?" It's a yes-no proposition. Design validation -- which is closer to what NIST wanted to do with WTC -- is a matter of asking lots of questions that have quantitative answers.

And it might also be the case for some people that running off a few examples of the product for destructive testing -- either for certification or as a design validate -- is less expensive. I've done that too. When I was designing injection-molded optics carriers I ran off stereolithographic copies of them for physical testing. That cost me only a few dozens of dollars and was ultimately cheaper and faster than FEA would have been. But that's not the case for large, complex, or expensive items.

Again I think reliance on the simulations is overstated.

If you can't demonstrate competence in high-stakes, big-ticket engineering, then it doesn't matter what you think. The fact remains that when talking about buildings and airliners, this type of testing is the norm.

[JayUtah]

dinAlt: You are correct in identifying the professor's analysis of the collapse as ad hoc.

A professor of physics is not automatically a structural engineer, and physics is not automatically engineering. Yes, perhaps engineering is a "crude" application of physics, but it's the right profession for this problem. When your car is broken do you take it to an automotive designer, or to a mechanic? When you are sick, do you go see a microbiologist or do you go see a doctor?

Engineering is based on physics, but it takes elementary physics farther than the typical physicist is interested.

This is why I would like to see an analysis of the collapse made by qualified personnel.

It has been; but people reject the results largely for political or ideological reasons. Oh sure, they try to offer evidentiary reasons, but they boil down simply to an unsupported unwillingness to address the results. "How can these models work?", etc. That's just FUD. They're trying to undermine credibility at all costs, regardless of whether the objection actually makes sense. It goes back to people thinking that their intuitive and simplistic understanding of something is equivalent to that applied by experts.

The other issue is the intuitive expectation that a global collapse should not have occurred. Structural engineers are not mystified in the least by this. Once collapse initiates, some degree of progressive collapse -- and perhaps even global collapse -- is inevitable. The WTC structure is simply one of the designs that was especially sensitive to failure progression. Not all steel structures are, nor are all core/tube designs.

NIST didn't put much effort toward studying the collapse progression or the global failure because there wasn't really any question that it should have occurred. To a structural engineer it's like trying to ask why a potato chip crumbled when you stepped on it.

I would like to be able to say, with confidence, this is what we should have expected. I currently have to admit that I don't know.

It doesn't surprise me at all. Down is the natural direction for things to fall. Intuition (wrongly) suggests that the underlying structure should have been stiffer or more robust in some way, and should have slowed or deflected the collapse. The notion at play here is what we call the "size effect". That is, certain materials properties and behaviors don't scale with the material.

Concrete, for example, has a fracture zone of a few centimeters. A "fracture zone" is the area around the tip of a crack that exhibits some degradation as the result of strain deriving from the crack. The mechanics of the continuation of the fracture depend in part on the geometry of the fracture zone. Basically if the size of the fracture zone is a significant percentage of the overall dimension, the fracture obeys certain properties of plasticity and elasticity. If the fracture zone size is very small proportionally, the object obeys brittle fracture mechanics. So a 5 m long concrete beam will behave elastically, while a 700 m dam will behave brittly. Why? Aren't they the same material?

That's one example of materials properties that don't scale. Fracture mechanics has little specifically to do with what I'm trying to say here, but it's an easy example. The underlying phenomenon is the size of material units. Concrete is made of fixed-size aggregates. You can use pea gravel as an aggregate when pouring a driveway, and pea gravel as an aggregate when pouring a dam. Some materials properties are functions of the aggregate size, not the size of the final product. Metal is made of crystals, and the size of the crystals determine the scale of certain properties.

But the notion of a 1,400-foot building made of steel being somehow very strong simply because it's made of steel is the wrong way to think about it. At the scale of the WTC construction and at the magnitudes of energies involved, steel can shear like paper or snap like a twig with seamingly little resistance. It's like a ten-foot high model of the building made with dry spaghetti and tissue paper. A ten-foot model made with scaled-down steel won't respond the same way as the full-sized building.

We are dealing with a complex system, where intuition and common sense do not necessarily apply.

Exactly. A person holding a PhD in physics or electrical engineering or computer programming, who does not have training in structures or the specific analytical methods associated with them, is still using intuition when he talks about things outside his training and experience. I'm well-qualified to discuss various things, but not -- for example -- corporate finance. I have relevant beliefs founded on intuition, but I can't imagine that my beliefs capture the sophistication and requirements of high finance.

Do you know if software currently exists to model this type of dynamic system?

Yes and no. ANSYS -- the current state of the art -- has collision and impact modeling, but cannot currently accommodate an appropriately detailed model of the entire structure. Increasing the subdivision results in a square of the number of constituent elements, and the computational complexity is further proportional to the square of the number of elements. I spoke with ANSYS representatives two weeks ago as part of the normal course of business, and since I have been following this discussion elsewhere for that long, I talked with them a little about the limitations. It has to do partly with the limitations built into the software -- some of them akin to the Y2K problem -- that are being addresssed now, and also with the fact that no computer exists in the unclassified world to run such a simulation.

[JayUtah]

Is that [localized temperature] discussion part of this thread?

Yes, I wrote on the topic above.

That's exactly what I was asking, what is the explanation for the apparently contained yet intense fires?

The explanation is that this is the nature of fires. You seem to be operating from a wrong assumption that temperature profiles in a fire remain fairly invariant over time and space. That is not the case. Temperatures at any point in space vary greatly over time, and temperatures at any one instant vary greatly from point to point. As I mentioned for example, air near the ceiling of a contained fire can be 1,000 C while air near the floor can be as cold as 200 C. Pointing out that the "average" temperature is 600 C is irrelevant -- only some of the environment will actually be at that temperature. And if something bad is supposed to happen at 1,000 C you want to know whether that temperature was achieved at any point, not whether it was achieved in general or over a wide area.

The WTC fires had sufficient air. The estimation of stoichiometrics based on smoke characteristics is wrong because it presumes the wrong kind of combustible. And in any case, we know that radiant properties are a greater determinant of temperature than air supply. As I said, the more air you provide, the cooler the fire burns. This may seem counterintuitive, but it's an empirically determined fact.

So in short, you want an "explanation" for a situation you claim is anomalous, but I don't see where you've shown that it's really anomalous. You simply state expectations as if they were self-evident fact. Maybe you don't know that you're making unsupportable assumptions, but that's the danger of being a layman and why none of these conspiracy theories are credible.

The argument has been skewed between the molten metal...

Well, we can pick this up later. It wasn't my intention to spend so long on the melted-steel tangent.

I appreciate your zealous defense, but you've been tending to be confrontational about claims I've never made.

I apologize if I've put words in your mouth. I dislike having them put in mine and so I really do try not to do it to others.

Regarding the zeal -- you are making erroneous and naive assertions in my field of expertise. Why should I not hold your feet to the fire on them?

I made the simple statement that they had to verify their models with the visual evidence, which you have previously agreed with. Nobody ever said it was "improper" or "not empirical", you're just being paranoid.

I'm sorry; I misunderstood the context of your statement. It sounded to me like you were arguing they should have been sifting through steel rather than looking at photographs in order to validate their computer models. If that's not what you were trying to say, then we likely agree. Photographic information of an unfolding disaster is extremely valuable. Recovered debris is often helpful, especially when it can be recovered in situ, but in that case you still have it only in a final form and you aren't always sure what story unfolded to get it in that state.

Whoa, just to interject, but what kind of supercomputer can only run for two weeks and then loses all of its data?

The kind that relies on massive parallelism, which is almost all of them. And you are exaggerating the characteristics of the danger.

Parallel processors rely on large numbers of computational elements working together in concert. Each processor is responsible for computing and storing a part of the overall solution locally. But as I explained before, the solution progresses from step to step by sharing information at each step between processors over a high-speed network. So if a processor craps out in the middle, it is unable to provide its results to those who need it, halting the whole computational process. And it is not possible to substitute another processor for the failed one, because it would need to be brought up to that point in the (collective) computation, and that requires all the prior intermediate results from other processors, which have now been forgotten in favor of storing the current intermediate result.

If you have a situation where N independent items must all work together and the MTBF of each item is H hours, then the mean time to failure for the entire system is H/N hours. We routinely supply systems with 1,000 or more processors. If the MTBF for the whole system is three weeks (500 hours) then this is really saying that the MTBF of each processor is 500,000 hours, which is pretty good for a processor. "Failure" in this case is not just hardware failure or mechanical failure, but also software failure -- anything that keeps that CPU from doing its job. We routinely have thermal, electrical, and acoustic situations that cause individual processors to fail. It's just the natures of the machine and problem.

It's not that the entire computer loses all its data every two weeks. It's simply that after two weeks, the probability of an individual failure that will ruin the results of a pending run increases to a significant value. Since you have to start over if it fails (checkpointing is prohibitive), you want to keep your problems as small as you can to avoid a high failure rate. It's better to structure your problem so as to require several small runs than a big problem requiring one big run.

Then you are correct, these are state-of-the-art models, but I was also correct that they are inaccurate and incomplete.

Immaterial. It is not possible ever to have 100% fidelity in any kind of model or reconstruction, whether digital, physical, or purely conceptual. So there's no point in saying that one modeling technique is not as good as another because it doesn't achieve 100% fidelity. FEA models properly constructed are no more "inaccurate" or "incomplete" than any physical recreation would be.

You continue to defy an entire industry -- several, in fact. As I mentioned, these state-of-the-art models, in their "inaccurate" and "incomplete" forms, have almost completely supplanted physical models for design evaluation in major engineering. They are simply better. They achieve as good or greater fidelity than physical models, and provide better insight. I'm talking about people like Northrup-Grumman (aircraft, spacecraft, ocean-going vessels), Lockheed-Martin (aircraft, spacecraft), Ford, John Deere, and Audi (automotive), and Alliant Technologies (munitions, launch vehicles) and other heavyweights in engineering. These are people who lay out billions of dollars annually in research and development, and risk all that on the fidelity of the kinds of solutions I provide.

Done, it still looks like they ran the impact simulation a single time.

No. They did an undetermined number of preliminary tests to determine the gross characteristics of the problem (Summary report, pp. 105-106).

Based on this, they identified four cases that would be studied in full, based on different estimates of speed and approach angle (p. 106; cf. also Table 6-5). Each of these were run, and each took approximately two weeks (p. 108).

So the fires lasted 15-20 minutes then the building slowly collapsed on itself as it cooled down?

Not exactly. The fire progressed from place to place within the building between impact and collapse. Fire follows fuel. We are accustomed to thinking the heat loading alone will -- or can -- cause structural problems. But the cooling cycle itself is dangerous. Fig. 6-11, p. 96 shows the geometric response of a floor truss that has been subjected to a certain degree of thermal stress. It deforms downward in the center, and this deflection imposes a certain tension at the endpoints. When the truss cools, it regains any strength that was lost during the heating, but it does not regain its shape; the center does not spring back up and render the truss horizontal again. In fact, because the truss is now contracting thermally, it adds tension to the endpoints -- something like 14 kips if memory serves. That is probably enough to buckle a perimeter column.

The cycles of heating and cooling work together to reduce the strength of structural members and/or physically pull them out of proper alignment. The entire building didn't heat up and cool down at once. There were localized zones of heating and cooling occurring at different times.

I've been explaining why, they are incomplete. But really, nothing but computer models? They don't ever stress test materials? Ever?

Oh, yes. Of course. The results of those tests are what go into the boundary conditions -- those constitutive relationships I spoke about. In the CSD code of LS-DYNA, the computational kernel of ANSYS, the boundary conditions between the various structural primitives are derived from empirical measurements. That type of measurement is actually what NIST does exceptionally well. Fig. 5-4, p. 68 of the summary report gives an example of the type of materials testing done on actual recovered steel from the site. The numbers in this data feed into the CSD model and determine the exact response of the material under the computed loads.

I know it's frustrating when everyone else isn't as smart and experienced as you, but thats why it's an open discussion.

Well, I'm not trying to be arrogant or elitist. This just happens to be one of the things I know very well. It's what I do. And yes it is annoying when people assert that their lay intuition or marginally-relevant experience should take precedent. But I'm trying not to be annoyed to the point of unpleasantness or mean-spiritedness. I'm simply pointing out where your thinking fails and asking you either to shore it up or retract it.