Gaffney takes on the 9/11 Commission

[mhgaffney]

Former 9/11 Commissioner says WTC was "fragile at core"

In his 2009 book THE GROUND TRUTH, former 9/11 commissioner John Farmer implies that the World Trade Center collapsed because the structure was defective. On page 28 of his book Farmer writes that the WTC was "imposing from the outside" but "fragile at its core."

Farmer's statement is hogwash. The man is an attorney -- not an engineer. He served as legal counsel on the commission, and apparently knows nothing about the reserve capacity of the WTC. Which is typical of the panel as a whole. The members were mostly lawyers and politicians. Not surprisingly, the key issue of the reserve capacity of the WTC core was never once discussed in the 2004 9/11 Commission Report.

Yet, there is no excuse for Farmer's recent statement, i.e., his continuing ignorance. Why? Because the numbers about the WTC core's reserve capacity have been public knowledge since the release of the NIST Report in 2005. The numbers are in the NIST Report -- and they tell the tale. I will discuss them in a moment. The Catch-22 here is that the numbers are so deeply buried in the 10,000-page report that a person could search for weeks, indeed, for months, without ever finding them.

No doubt, the numbers were intentionally buried for this reason. They are certainly not mentioned in NIST's 50-page Executive Summary Report, in which NIST summed up its findings and presented its official WTC collapse model. The brief executive summary is the only part of the NIST Report that most people read, if they read anything.

This shows how easy it is to conceal the truth from the American people. As Allen Dulles reportedly said to other members of the Warren Commission who were worried that the public might see through the Warren Report: "Don't worry -- Americans do not read reports."

NIST's reluctance to discuss the WTC's reserve capacity in its executive summary is just one of many reasons why the NIST Report is a gloss -- and a sham. If the numbers about the WTC's reserve capacity had become more widely known, NIST's favored collapse model would have been exposed for what it is: ridiculous. So, it's no surprise that John Farmer never heard of this data.

I first presented the numbers regarding the WTC reserve capacity on this board in December 2006 in a footnoted paper -- and I have presented them several times, since. The reaction here was mostly ridicule. Nonetheless, the numbers are correct. They were correct then, and they are just as correct today.

I have in my possession a letter proving this. The letter was sent to me in December 2006 by the NIST scientific team -- set up to answer questions from the public about the 2005 NIST Report. With the help of the scientific team, I located the critical information about the WTC reserve capacity. Many of the scientists at NIST are honest. The question remains how the honest ones would allow the administrators who run NIST to package a sham report. But that would be a separate discussion.

The letter is below. I will explain it in the next post.

[mhgaffney]

The key numbers are the demand-capacity ratios for each of the 47 core columns in WTC 1. In the second page (below) the letter mentions that the numbers are to be found in NIST NCSTAR 1-6 (p. 233). I will post a link later for those who want to look.

But the key part of the NIST letter is the third paragraph from the bottom on page two (below). In the last sentence NIST states "The values reported ranged between 0.36 and 0.63, which correspond to reserve capacities ranging between 1.6 and 2.8 (not inconsistent with the value that you cited of 2.25)."

The number 2.25 is the average factor of safety of the 47 core columns. Factor of safety is derived from the demand-capacity ratios, and is another way of expressing the same data. I will explain its significance in a moment.

Actually, the number 2.25 did not come from me but from Wayne Trumpman, who posted one of the first critical analyses of the NIST Report on the Internet. (here)
http://portland.indymedia.org/en/2005/09/324507.shtml

Trunmpman started me thinking about the WTC reserve capacity and its factor of safety -- and so, I went to the NIST scientific team trying to prove or disprove Trumpman's figure. Based on the demand-capacity ratios I found in the NIST Report, however, I calculated that the average is actually 2.1. But Trumpman was close.

Here is what the number 2.1 means. The factor of safety of 2.1 means that an average core column could support more than two times the anticipated design load before incurring any structural damage. This means you could literally cut half the core columns and the WTC would continue to stand, no problem. You could actually cut more than half, for reasons I will explain in a later post.

Folks, 2.1 is a whopping number -- and it clearly shows that the official WTC collapse model is absurd. This is true even if you buy into the theory that the fires weakened the columns. Because remember -- at least half of the core columns were outside the impact zone, hence can have suffered no significant loss of insulation due to the plane impact. Therefore, at least half of the core columns were totally protected from the fires and could not have been weakened, even by the worst case fire scenario. With half the core columns intact - no way you can generate a collapse.

This shows that the impacts and fires could not have brought down the WTC -- even under the worst fire scenario you can imagine. No fire could weaken protected steel columns in a mere 1-2 hours.

[mhgaffney]

Here is a more detailed explanation of reserve capacity and factor of safety. The following appeared in my 2008 book. No one has shown any errors in this discussion.

The Issue of Reserve Capacity

As the NIST report states,

“both towers had considerable reserve capacity. This was confirmed by analysis of the post-impact vibration of WTC-2, the more severely damaged building, where the damaged tower oscillated at a period nearly equal to the first mode period calculated for the undamaged structure.” [my emphasis]61

The above passage informs us that WTC-2 gave no sign of instability after the impact of Flight 175. Unfortunately, although NIST’s summary report provides a wealth of information about how the World Trade Center was constructed it fails to clarify the matter of the WTC’s “considerable reserve capacity.” At any rate, I scoured the report in vain for a clear discussion of this important issue. In frustration, I finally called NIST for assistance and was guided to several of the project reports and supplementary documents. I also consulted with Gary Nichols, an expert at the International Code Council (ICC), and with Ron Hamburger, a leading structural engineer. These conversations were an education. I learned that estimating the overall reserve capacity of a steel structure is by no means a simple matter. Numerous factors are involved. Moreover, there are different ways to approach the problem.

Perhaps the simplest measure of reserve capacity are the standards for the material components of a building. In the late 1960s when the WTC was constructed the applicable standard was the New York City Building Code, which required a builder to execute computations for the various structural members to show they met the specified requirements. However, the code also allowed for actual testing of members in the event that computations were impractical. The testing standards applicable in 1968 give a reasonable idea of the required level of reserve strength in the steel columns and other materials used in the WTC. For example, in the most stringent test a steel member had to withstand 250% of the design load, plus half again its own weight, for a period of a week, without collapse.62

Factor of Safety

Another widely used measure of reserve capacity is the so called “factor of safety.” This varies for different structural elements, but for steel columns and beams typically ranges from 1.75 - 2.0.63 The NIST report actually breaks down this more general figure into two separate and slightly different measurements for stress: yielding strength (1.67) and buckling (1.92).64 For our purposes, however, the more general figure is adequate. So, for example, a steel column with a factor of safety of 1.75 must support 1.75 times the anticipated design load before it begins to incur damage. While this value is typical of steel beams in general, the actual reserve strength of the steel columns in the WTC was higher. When NIST scientists crunched the numbers for the 47 core columns of WTC-1 (in the impact zone, between the 93rd and 98th floors) they calculated that the factor of safety ranged from 1.6 to 2.8, the mean value being 2.1.65 This means that the average core column in the impact zone of WTC-1 could support more than twice its design load before reaching the yield strength, i.e., the point where damage may begin to occur. My grateful thanks to the NIST investigative team for helping me locate these numbers, which were buried in the report.

It is important to realize that the factor of safety is not a threshold for collapse, but a value beyond which permanent damage may begin to occur. As the NIST report admits, even “after reaching the yield strength, structural steel components continue to possess considerable reserve capacity.”66 This is why steel beams and columns typically do not fail in sudden fashion. The loss of strength is gradual. No doubt, this helps to explain why, although fires have ravaged many steel frame buildings over history, none had ever collapsed–––until 9/11–––nor has any since. What all of this means, of course, is that even in the most improbable worst case, in which many or all WTC core columns lost half of their strength, there was still sufficient reserve capacity to support the building.

The Perimeter Wall

With regard to the WTC’s perimeter columns, the factor of safety fluctuated from day to day and even from hour to hour, because, in addition to supporting 47% of the WTC’s gravity load, the perimeter wall also had to withstand the lateral force of the wind, which is highly variable given the whims of Mother Nature. A single face of the WTC presented an enormous “sail” to the elements, for which reason John Skilling vastly overbuilt this part of the structure. According to the NIST report, the outer wall’s factor of safety against wind shear on September 11, 2001 was extraordinary, i.e., in the 10-11 range.67 Why so high? The answer is simple: On the day of the attack there was essentially no wind, only a slight breeze.68 For this same reason nearly all of the perimeter wall’s design capacity was available to help support the gravity load. As the NIST report states, “On September 11, 2001 the wind loads were minimal, thus providing significantly more reserve for the exterior walls.”69 When NIST crunched the numbers for a representative perimeter column in WTC-1 (column 151, between the 93rd and 98th floors), they arrived at a factor of safety of 5.7.70 Assuming this average figure is a typical value we arrive at a reasonable estimate of the perimeter wall’s amazing reserve capacity. Even if we subtract those columns severed/damaged by the impact of Flight 175, and the lost capacity due to the alleged (but unproven) buckling along the eastern perimeter wall, there was still a wide margin of safety, more than enough by several times over to support the outer wall’s share of the gravity load, with plenty to spare.71 I must emphasize: These are not my numbers. They are NIST’s own figures.

The WTC’s tremendous reserve capacity was no secret. In 1964, four years before the start of construction, an article about the planned WTC appeared in the Engineering News-Record. The article declared that “live loads on these [perimeter] columns can be increased more than 2,000 percent before failure occurs.”72 A careful reading of the piece also gives insight into why the plane impacts were not fatal to the integrity of the outer wall. The reason is simple: the perimeter columns were designed to function together as an enormous truss, specifically, a Vierendeel truss. The wall was inherently stable. After the plane impacts it behaved like an arch, simply transferring the load to the surrounding columns. As the 1964 article states,

“the WTC towers will have an inherent capacity to resist unforeseen calamities. This capacity stems from its Vierendeel wall system and is enhanced through the use of high-strength steels.”73

In short, NIST’s own data fails to support its conclusions about the cause of the WTC collapse. The official theory requires the fatal weakening of both sets of columns, and NIST came up short on both counts due to insufficient evidence. Indeed, I would call it woefully insufficient.

Notes:

61 NIST NCSTAR 1, Full Summary Report, WTC Investigation p. 144.

62 In the code his was sub-article 1002.0, adequacy of the structural design. See NIST NCSTAR 1-1A, WTC Investigation, p. 32.

63 Conversation with Ron Hamburger, structural engineer, Dec 7, 2006.

64 NIST NCSTAR 1-2, WTC Investigation, p. 66.

65 In the NIST report the reserve capacity data is expressed in the form of demand/capacity ratios, which is simply another way of expressing the factor of safety. I use the latter because I feel it’s more comprehensible to the average lay person. Personal communication, December 14, 2006. See NIST NCSTAR WTC Investigation 1-6, Figure 8-9, p. 233.

66 NIST NCSTAR 1-2, WTC Investigation, p. 66.

67 NIST NCSTAR 1-2, WTC Investigation, p. cxii; also see NIST NCSTAR 1-2, WTC Investigation, p. 84. 

68 The NIST report states: “on the day of the attack the towers were subjected to in-service live loads (a fraction of the design live loads) and minimal wind loads.” NIST NCSTAR 1-2 WTC Investigation, p. liv.

69 NIST NCSTAR 1-2, WTC Investigation, p. 66.

70 I received clarification about this from the NIST WTC Investigation Team. Personal communication, December 14, 2006. The number 5.7 is derived from values presented in Figure 4-35, NIST NCSTAR 1-6, WTC Investigation, p. 101. 

71 NIST NCSTAR 1-2, WTC Investigation, p. 66.

72 “How Columns Will Be Designed for 110-Story Buildings,” Engineering News-Record, April 2, 1964.

73 Ibid.

[mhgaffney]

The demand capacity ratios can be found here -- on page 233
http://wtc.nist.gov/pubs/NISTNCSTAR1-6Draft.pdf

From this data, anyone with average math ability can confirm that the 2.1 number is the correct average factor of safety for the WTC core columns.

[mhgaffney]

With regard to the insulation on the core columns - NIST assumed that 100% of the insulation was lost due to the plane impact. Anything LESS than 100% and you can't get a collapse. Even a partially insulated steel column has enough protection to withstand a fire lasting only 1-2 hours.

NIST never showed that 100% of the insulation was lost, in any event. This was yet another assumption by NIST.

[Rohirrim]

Have you seen the recently released NYPD aerial views of the collapse of the towers? Certainly no evidence of explosives there. Very clearly it is structure collapse.

[W*GS]

Thanks for wasting the time of honest people with your dishonest lying filth.

[mhgaffney]

The usual non response.

Again, the numbers do not lie. I already gave the link. But today I will scan and post the page from the NIST Report with the demand capacity ratios --

As I stated -- anyone can crunch the numbers. The math is simple. Any eighth grader can calculate the mean or average.

[W*GS]

How many of the honest engineers and scientists at NIST would endorse your whacked-out crap, gaff-o?

Quit using their verification of your arithmetic as some sort of approval of your BS.

[mhgaffney]

I've scanned the pertinent page from the NIST Report. I gave the link above. Here are the demand-capacity ratios for all of the 47 core columns in WTC-1.

This data also gives the factor of safety for each column. Anyone who knows how to divide can do this.

The numbers prove that the core of the WTC was anything but "fragile."

[The Lone Bolt]

Why present this to us? Take it to the architects and engineers at JREF and see what they think.

[bpc]

Maybe if you offer a blow job to Van Jones, he'll put you on and give you a public forum to discuss your trash? Just a thought.

BTW, your kind is what truly makes America so great. Land of the free... land of free speech. Gotta love it.

[The Lone Bolt]

I posted your argument at JREF. Here's a simple and reasonable countreargument:

Originally Posted by ElMondoHummus

But waitaminute... How's any calculated capacity supposed to matter when the presumption is an intact structure? If he's discussing the WTC columns, then he's disucssing a system where the vertical columns are meant to only handle pure vertical loads, and loads during the collapse were eccentric. Furthermore, the WTC columns had no capacity whatsoever when the floor assemblies were torn away, and that's really the key to understanding 9/11: Most of the falling debris severed the floors, and when those went, the load capacity of the columns became a moot point since they couldn't stay in place on their own without the floors to hold them up.

Sounds like a good point that even a neophyte like me can understand. Basically, when the structures were damaged the vertical columns were subjected to non-vertical loads that they weren't designed for. Furthermore the floor assemblies were keeping the vertical columns in place and when they went the columns were unsupported and thus collapsed as well.

[W*GS]

Gee, imagine if gaff-o knew anything about architecture, engineering, or structural design. He might make less of an ass of himself.

[The Lone Bolt]

For anyone who wants to read more counterarguments, here's the link: http://forums.randi.org/showthread.php?t=167191

I think these guys demolish Gaff's argument.

[mhgaffney]

Garbage. Your expert is already presuming a collapse in progress.

But how did the collapse even begin? Given the videos and photos from 9/11 -- each of the twin towers began to fall all at once. This means every single core column failed at the same instant. But this is not possible without explosives.

Even when steel fails it does not snap. It is a gradual process. As NIST itself concedes -- even if the yield point is reached -- steel has a substantial reserve capacity. Which means that even if the yield point is exceeded -- the failure would be slow and gradual. Your expert jumps the gun.

The failure of a few floors in the impact zone is trivial to the overall structure.

[W*GS]

Originally Posted by mhgaffney

But how did the collapse even begin? Given the videos and photos from 9/11 -- each of the twin towers began to fall all at once.

No, they didn't.

You must be blind.

Originally Posted by mhgaffney

The failure of a few floors in the impact zone is trivial to the overall structure.

To the "overall structure"? Perhaps. To the floors immediately below, certainly not. One or two floors fail, and land on the floor below. Never designed to withstand that much energy, it too fails, then the floor below, and the next floor down, and so on.

Do you even get that?

[Tombstone RJ]

People need to quit attacking Gaff for this analysis. Fact is, the WTC were OVERBUILT, if anything.

The WTC towers were the first of it's kind, they were the tallest buildings in the world (I believe, might be wrong here) at the time they were built. The guy who designed the buildings anticipated an aiplane crash and built the WTC towers to withstand just such a tragic event.

There's only two real possibilities: 1. the man who originally designed and built the WTC did not know what he was doing and consequently did not build the WTC as tuff or as thoroughly as he thougt or 2. other forces than the planes themselves caused the towers to collapse.

Now, I'm not a conspiracy theory proponent. But, I'm not gonna blast gaf for doing some critical research on an extremely important topic.

I don't want to believe the US government had anything to do with 911. It goes against everything I believe in. However, IF there is evidence of a betrayal by the US government on the American people, then it needs to be exposed.

I still don't like what happened at the Pentagon. I think that situation is tenuous at best. There is a video somewhere that shows a plane flying into the Pentagon but for whatever reason, no one can account for that video, why?

[The Lone Bolt]

Originally Posted by mhgaffney

Garbage. Your expert is already presuming a collapse in progress.

But how did the collapse even begin? Given the videos and photos from 9/11 -- each of the twin towers began to fall all at once.

All the video evidence show the exact opposite, that the collapses begin at the point of impact of the planes. I can't believe that even you could be so deluded as to see anything else.

Originally Posted by mhgaffney

Even when steel fails it does not snap. It is a gradual process. As NIST itself concedes -- even if the yield point is reached -- steel has a substantial reserve capacity. Which means that even if the yield point is exceeded -- the failure would be slow and gradual. Your expert jumps the gun.

Feel free to go to JREF and explain it to him. I think you're wrong.

Originally Posted by mhgaffney

The failure of a few floors in the impact zone is trivial to the overall structure.

Not at all. The idea is that when one floor collapses onto the next and that floor collapses, the next floor down has to contend with the mass and momentum of two floors and then next three floors and so-on. This is what they refer to as the "snowball effect." Pretty soon the mass and momentum is unstoppable (especially with the weakening of supporting trusses due to fires on several floors).

[The Lone Bolt]

Originally Posted by Tombstone RJ

People need to quit attacking Gaff for this analysis. Fact is, the WTC were OVERBUILT, if anything.

The WTC towers were the first of it's kind, they were the tallest buildings in the world (I believe, might be wrong here) at the time they were built. The guy who designed the buildings anticipated an aiplane crash and built the WTC towers to withstand just such a tragic event.

There's only two real possibilities: 1. the man who originally designed and built the WTC did not know what he was doing and consequently did not build the WTC as tuff or as thoroughly as he thougt or 2. other forces than the planes themselves caused the towers to collapse.

Now, I'm not a conspiracy theory proponent. But, I'm not gonna blast gaf for doing some critical research on an extremely important topic.

I don't want to believe the US government had anything to do with 911. It goes against everything I believe in. However, IF there is evidence of a betrayal by the US government on the American people, then it needs to be exposed.

I still don't like what happened at the Pentagon. I think that situation is tenuous at best. There is a video somewhere that shows a plane flying into the Pentagon but for whatever reason, no one can account for that video, why?

Gaff simply doesn't have a case. That's why we are questioning his reasoning and evidence.

And I don't follow you about the Pentagon plane. Video shows what appears to be a large passenger jet flying into the Pentagon, exactly as per the widely accepted version of events. What's your point?

[mhgaffney]

Lone Bolt,

FYI, NIST concedes in its report that the impact did not cause the collapse. According to NIST the twin towers would have stood indefinitely -- after the impacts. This confirms what I said above: A few collapsed floors from the impact was trivial.

You appear to be unfamiliar with NIST's collapse theory. They claimed the impacts jarred loose 100% of the insulation from the steel columns -- which made them vulnerable to the fires. The steel columns weakened due to the heat -- then failed.

But there are many problems with NIST's collapse theory. Here are a couple:

1. NIST recovered two core columns from the impact zone of WTC 2. Yet, NIST found zero evidence on those columns of any deformations, slumping, bowing, sagging that you would expect if fire had weakened the columns. I repeat: zero evidence.

In fact, NIST produced no evidence that any of the core or perimeter columns failed due to heat. If someone knows of some evidence, please show me because I have yet to see it.

2. NIST's claim that 100% of the insulation was knocked loose is contradicted by photos in the NIST Report -- which show that a considerable part of the insulation on the perimeter columns remained intact after the impact. We will never know the actual percentage of insulation lost -- but it was considerably less than 100%. NIST contradicts itself regarding the loss of insulation.

Yet NIST's collapse model assumes 100% loss of insulation, And given the way NIST had to tweak its computer model again and again -- the 100% figure was certainly a requirement. THis is the problem you find again and again. The assumptions in the official story turn out to be wrong. Garbage in garbage out. The conclusions are also wrong -- or very at least unsupported.

[The Lone Bolt]

Originally Posted by mhgaffney

Lone Bolt,

FYI, NIST concedes in its report that the impact did not cause the collapse. According to NIST the twin towers would have stood indefinitely -- after the impacts. This confirms what I said above: A few collapsed floors from the impact was trivial.

You appear to be unfamiliar with NIST's collapse theory. They claimed the impacts jarred loose 100% of the insulation from the steel columns -- which made them vulnerable to the fires. The steel columns weakened due to the heat -- then failed.

Based on this comprehensive investigation, NIST concluded that the WTC towers collapsed because: (1) the impact of the planes severed and damaged support columns, dislodged fireproofing insulation coating the steel floor trusses and steel columns, and widely dispersed jet fuel over multiple floors; and (2) the subsequent unusually large jet-fuel ignited multi-floor fires (which reached temperatures as high as 1,000 degrees Celsius) significantly weakened the floors and columns with dislodged fireproofing to the point where floors sagged and pulled inward on the perimeter columns. This led to the inward bowing of the perimeter columns and failure of the south face of WTC 1 and the east face of WTC 2, initiating the collapse of each of the towers. Both photographic and video evidence—as well as accounts from the New York Police Department aviation unit during a half-hour period prior to collapse—support this sequence for each tower.

http://wtc.nist.gov/pubs/factsheets/faqs_8_2006.htm

Where does it say that "the impacts jarred loose 100% of the insulation from the steel columns", or that such complete removal of the insulation was needed?

And you overlooked the trusses which held up the floors, as well as the effects of the sagging floors on the columns.

In any event it doesn't look like NIST's position is that "the twin towers would have stood indefinitely -- after the impacts" or that the plane crashes did not lead to the collapses of WTC 1&2.

But there are many problems with NIST's collapse theory. Here are a couple:

1. NIST recovered two core columns from the impact zone of WTC 2. Yet, NIST found zero evidence on those columns of any deformations, slumping, bowing, sagging that you would expect if fire had weakened the columns. I repeat: zero evidence.

In fact, NIST produced no evidence that any of the core or perimeter columns failed due to heat. If someone knows of some evidence, please show me because I have yet to see it.

Funny you should bring this up. The JREFers also have a response:

Originally Posted by ElMondoHummus

NIST found no evidence on these columns of any deformations, sagging, bowing, slumping on these columns"?? Forget NCSTAR 1-6D, did he read 1-3C at all? Even I know where to find that, and I've never read the entire report!

Good grief... it's one thing to make an argument, it's a whole other thing entirely to try and state something refutable by a simple search. NCSTAR 1-3C specifically exists to list these sorts of distortions of the steel columns; that's why the subreport's name is "Damage and Failure Modes of Structural Steel Components"! I mean, my God, it's even got pictures! I'm serious! There is actual photography of representative steel elements, including core columns, perimeter columns and panels, trusses, spandrel plates, and all sorts of other steel assemblies that had been present in the towers. That report's name makes its contents obvious, but yet he tries to say that?

Lone Bolt: Gaffney seems to be good "ignore list" material on whatever forum you're seeing him post on. He's stated a pair of outright falsehoods that are easily refutable by going to the source material and looking for one's self, like I did. He's wrong about NIST not finding any evidence of "deformations..." etc., and he's dead wrong about their report not mentioning creep. He sounds like a guy willing to retail lies about the topic, and combating every single falsehood will turn you into nothing other than a data aggregator and collator. I'd just point out a couple of outright lies as representative - such as these, since you already have the material refuting you in front of you - and then tell him "bye bye". He seems to be the sort of person too lazy to drown people in accurate detail, so therfore makes things up and tries to sound authoritative about it. He's not worth interacting with. Not when he pitches out easily hittable softballs like these.

[SoCalBronco]

[mhgaffney]

Bolt,

Sure, the WTC ruin was a pile of twisted and deformed steel. There was huge deformation during the collapse.

But if the fires caused the steel to fail you would expect to find evidence for this. NIST recovered two core columns from the impact zone of WTC 2 -- where the fire was hottest and where the collapse began. Yet, NIST found no evidence the columns had even been exposed to high temperatures! This is astounding.

A steel column weakened by fire will slump and sag in a characteristic way -- yet again NIST produced no such evidence.

Here's the source:
http://wtc.nist.gov/pubs/NISTNCSTAR1-3Draft.pdf

I suggest you read from page 94 through 95.

Out of 170 steel samples tested by NIST, only three had been exposed to temperatures above 250 C. Not even one steel sample had been exposed to temperatures higher than than 625 C.

This is astonishing. If the fires were so intense -- there should be evidence. But NIST found none.

[mhgaffney]

Bolt

NIST did assume that 100% of the insulation was lost as a result of the plane impact. Here is the verbatim passage. SFRM = insulation:

Prior to aircraft impact, the SFRM was assumed to be consistent with the as-built condition and
characterized by a uniform equivalent thickness. If a structural element was found to be in the
path of a debris field of sufficient intensity, all the insulation (SFRM and gypsum board) was
deemed to have been removed.

source -- scroll to page xliv
http://wtc.nist.gov/pubs/NCSTAR1-5ExecutiveSummary.pdf