NIST’s Estimate of Fire Damage to North Tower

[Kevin Fenton]

All the page references here are taken from: http://wtc.nist.gov/pubs/NISTNCSTAR1Draft.pdf
Information about NIST’s estimate of the temperatures of the fire in the North Tower can be found in Chapters 2 and 6 of the report.

Fireproofing
First of all, to assess the amount of fire damage we need to look at the extent of fireproofing that was knocked off, as “the buildings would likely not have collapsed under the combined effects of the aircraft damage and subsequent fires, if the insulation had not been widely dislodged.” (Page 149/203) NIST determined the extent of damage to fireproofing using a computer simulation and these are the results it came up with:

93rd floor “The light debris did minimal damage … to the thermal insulation on the trusses of the composite floor system supporting the 94th floor.” (Page 20/74)

94th floor “The insulation applied to the floor trusses above and the columns was scraped off by shrapnel-like aircraft debris and building wall fragments over a wedge almost 100 ft wide at the north face of the tower and 50 ft wide at the south end of the building core.” (Page 20/74)

NIST do not comment on the loss of fireproofing on the 95th floor.

96th floor “The insulation was knocked off nearly all the core columns and over a 40ft width of floor trusses from the south end of the core to the south face of the tower.” (Page 21/75)
Whether the fireproofing was knocked of here is particularly significant, as NIST thinks the collapse was initiated on the south side due to floor failure.

97th floor. “The debris cut a path through the west and center array of trusses and core columns, stripping the insulation over a 90ft wide path. The insulation was stripped from a 50 ft wide path on the south side of the floor space.” (Page 22/76)
That so much insulation was lost on this floor, especially on the other side of the core, is remarkable, as it was hit neither by the fuselage nor one of the engines, merely by a section of the aluminium wing.

98th and 99th floors. “The debris cut a shallow path through the west and center array of trusses, damaging the insulation up to the north wall of the building core.” (Page 22/76)

The total result of this was “Insulation stripped from trusses covering 60,000 ft2 of floor area.” (Page 23/77)
Perhaps surprisingly, this was far less insulation than NIST thinks was stripped from the South Tower.
Whilst the pieces of aircraft debris quite clearly retained the ability to damage insulation after penetrating the perimeter, one might think that the figure of 60,000 ft2 of floor area (plus 43 of the 47 core columns) is a little on the high side, at the very least. In particular I doubt that the debris would have retained the momentum to strip insulation from a 50 ft wide area on the south side of the core.

How did NIST arrive at this figure of 60,000 ft?
“The dislodgement of thermal insulation from structural members could have occurred as a result of direct impact by debris … In interpreting the output of the aircraft impact simulations, NIST assumed that the debris impact dislodged insulation if the debris force was strong enough to break a gypsum board partition immediately in front of the structural component. Experiments at NIST confirmed that an array of 0.3 inch diameter pellets travelling at 350 mph stripped the insulation from steel bars like those used in the WTC trusses.” (117/171)
So, if the fireproofing on a component was hit by an array of 0.3-inch pellets, the component was bereft of fireproofing for the purposes of the computer simulation.

On what is NIST’s estimate of the fire temperatures based?
Some steel sections were recovered from the fire-damaged floors. Specifically, NIST obtained 26 exterior panels from the North Tower, along with eight core column parts from WTC 1. (Page 85/139) 16 of these panels were from the fire-affected areas. They were tested to find what temperature they had reached and NIST found that “Of the more than 170 areas examined on 16 perimeter column panels, only three columns had evidence that the steel reached temperatures above 250 degrees C: east face, floor 98, inner web; east face, floor 92, inner web; and north face, floor 98, floor truss connector. Only two core column specimens had sufficient paint remaining to make such an analyses, and their temperatures did not reach 250 degrees C.” Page 88/142
Well, that’s not much to go on, but I’m sure it helped them model the fires.
“NIST did not generalise these results, since the examined columns represented only 3 percent of the perimeter columns and 1 percent of the core columns from the fire floors.” Page 88/142
So they ignored the only direct evidence they had then?
“Nonetheless, these analyses indicated some zones within the WTC 1 where the computer simulations should not, and did not predict highly elevated steel temperatures.” Page 89/143
Meaning that they at least tweaked the software before beginning to ignore them.

If the steel samples were not used to predict how hot the fires were, what was?
The starting point for NIST’s estimates was provided by photos and videos, but in a section entitled “Need for Simulation” on page 118/172 they say, “… the cameras could only see the periphery of the building interior. The steep viewing angles of nearly all of the photographs and videos further limited the depth of the building interior for which fire information could be obtained. NIST could not locate any photographic evidence regarding the fire exposure of the building core or the floor assemblies.
“The simulations of the fires were the second computational step in the identification of the probable sequences leading to the collapses of the towers.”
So, instead of consulting actual evidence, they used a computer. How very modern of them.

What other factors affected the fires?
Combustibles
“NIST estimated the fuel loading on these floors to have been about 4 lb/ft2 (20 kg/m2), or about 60 tons per floor. This was somewhat lower than found in prior surveys of office spaces. The small number of interior walls, and thus the minimal amount of combustible interior finish, and the limited bookshelf space account for much of the differences.” (Page 76/130)

Ceiling
Had a 1.2m soffit remained after the aircraft impact, this “would maintain a hot upper layer on each floor.” And would produce “A fire of longer duration near the core columns and the attached floor membranes.” Page 124/178
Did such ceiling remain?
“The University of Buffalo, under contract to NIST, conducted tests of WTC-like ceiling tile systems using their shake table (Figure 6-29) and impulses related to those induced by the aircraft impact on the towers. The data indicated that accelerations of approximately 5g would most likely result in substantial displacement of ceiling tiles. Given the estimated impact accelerations of approximately 100g, NIST assumed that the ceiling tiles in the impact and fire zones were fully dislodged. This was consistent with the multiple reports of severely damaged ceilings.”

So NIST thought the amount of combustibles was 4 lb/ft2 and that the soffits were dislodged and these are the values it used to determine whether/how (delete as applicable) the building collapsed after 102 minutes, right?
Wrong. If you look at Table 6-10 Comparison of Global Structural Model Predictions and Observations for WTC 1, Case B on page 148/202, you can see from the table’s name that NIST used “Case B” here, which was the case throughout the document. NIST used various cases (A, B, C and D) to estimate the damage to the towers (and whether it should cause them to fall over). Cases A and B apply to the North Tower, whereas Cases C and D apply to the South Tower. Cases A and C reflect NIST’s best estimates of the various variables affecting the towers’ performance, whereas Cases B and D are the best estimates usually increased by between 5% and 25%, to make the damage worse. If you look at Table 6-6 Values of WTC Fire Simulation Variables on page 124/178, you can see that the tenant fuel load for Case B is 5 lb/ft2 (not 4 lb/ft2) and that the soffit remained in place. If NIST thinks there are incorrect values, why is it using them?

Since, according to NIST, the North Tower collapsed primarily due to the fire damage, the extent of such damage is the key factor in this tower.

[JackRiddler]

1. as far as I can see...

Note that the 400-degrees C temp everyone here claims is "all you need" to weaken steel is reached only in a couple of spots in the simulation, not on any of the pieces you say they have.

Where do you get that they have that many real pieces?

The following graphic from the executive summary suggests they have only one core-column piece from the WTC 1 impact zone. Correct me if I'm misreading it:

[Kevin Fenton]

7. NIST Report

I got the bit about eight core column parts from page 85/139. However, they say that only two of them had enough paint for an analysis of the fire temperature - that's on page 88/142.

I don't know whether the piece in the picture (core 603) was one of the ones that had paint on it (and whose temperature was therefore determined) or not. Maybe the other WTC 1 core pieces weren't from the impact zone, so they're not shown in the photo.

What's wrong with the 911 truth website? That seemed a model of reasonableness to me.

[JackRiddler]

11. right, so it's true

One piece of core column (Core 603) is all they have from the impact zone (where the collapse initiates), plus presumably seven from the fire zones above that.

Any data on WTC 2? I know they have ZERO pieces from WTC 7, of any kind.

And on these slivers, plus a high-octane computer simulation that ends immediately on collapse initiation (since "gravity does the rest,") they pretend they're conducting a complete forensic examination.

---
Nothing's wrong with the 911Truth.org site. You're asking the wrong guy, I never called it a conspiracy site (with the usual connotation of "conspiracy," anyway).

[Kevin Fenton]

12. South Tower

Whereas NIST claims that the main factor in the North Tower was the fires, it claims the main factor in the South Tower was the impact damage (the different factors are supposed to be why the "wrong tower fell first"). You can find my post about the South Tower core damage here:
http://www.democraticunderground.com/discuss/duboard.php?az=view_all&address=125x53264

On page 85/139 it says that it recovered 16 exterior panels from the South Tower (against 26 from the North Tower), along with 4 core column sections (8 in the North Tower). Apparently "None of the nine recovered panels from within the fire floors of WTC 2 were directly exposed to fire."

I don't know how good the programming of the computer simulation is, but it obviously depends on the numbers they feed into it (i.e. how much insulation is stripped, how fast the plane is going, etc.). To me it looks like they took high-end estimates and bumped them up a bit, for example they say that 82 of the 94 core columns were stripped of insulation, some of them on multiple floors. I can see that some damage would be caused to core column fireproofing, but so much...

Did you get any reasons the 911truth website was banned, there wasn't even much about removal men there?

[pox americana]

2. More sleeping medicine for dopey Bushbots.

Of course it makes no sense whatsoever. The whole "insulation blown off by the plane crash" theory is laughable.

How exactly are airplane parts supposed to strip sprayed-on fibers off a steel truss, especially on the floors that had been redone? That stuff was over an inch thick. It was also protected by dropped ceilings on one side and a 4" concrete slab and steel floorplates on the other.

If anything blew the insulation off it was the thermite or nitro or whatever the hell they used to blow the buildings apart.

[Make7]

6. May I ask you a question or two?

Have you ever scraped the sprayed-on fire insulation off of any steel?

How exactly does a drop ceiling provide protection?

-Make7

[pox americana]

8. 1) Yes, it's like very thick paint,

and 2) whatever is supposed to have scraped it all off (flying barf bags?) would have hit the ceiling first, or the slab.

[Make7]

17. one hypothetical, one not

1. Did it seem difficult to scrape off the fire-proofing to you?
   
2. How far would you walk across a typical drop ceiling if you knew there was a two hundred foot drop directly below it?

[pox americana]

18. Fireproofing is basically insulation fibers suspended in glue.

I don't know exactly what compound the WTC used but yes, the stuff I've seen is very difficult to remove.

[Make7]

19. Interesting...

...I've removed some types of spray-on fireproofing with nothing more than a regular screwdriver and some of them were not difficult at all. (Although some of them were tough.)

-Make7

[Kevin Fenton]

21. The question is

NIST said fireproofing was stripped from trusses covering 140,000 square feet of floor area - 60,000 ft2 in the North Tower and 80,000 ft2 in the South Tower (the equivalent of 3.5 whole floors). Do you agree or disagree with this estimate?

[spooked911]

3. Good analysis, and not surprisingly, they are just making shit up

They were paid to prove airplane damage and fires led to global collapse, and dammit they tried their best to show just that.

What a joke.

[philb]

4. NIST stuff is hypothetical; this is factual

Gas fires were short lived. And its clear the area where plane hit wasn't very hot a little while after the crash.

http://www.democraticunderground.com/discuss/duboard.php?az=show_mesg&forum=125&topic_id=45004&mesg_id=45133

Simiarly, survivors and firemen in WTC2 said the fires there were fairly isolated and dying down.

http://thememoryhole.org/911/firefighter-tape-excerpts.htm
see 9:52

[philb]

5. Lots of the planes seemed to end up outside the buildings: so what got thr

ough? The heavy parts that would have penetrated don't seem to have had much coverage area. Maybe lower fuselage and engines. but the South Tower hit was in a corner and not directed at the core; and the fires were never major. Most of the gas seems to have exploded outside the building.


CAPTAIN MICHAEL DONOVAN FDNY WTC2 2nd plane hits

We were actually still on Church Street. We heard the plane briefly, the earth shook, the buildings shook, a tremendous fireball overhead.
I thought there was a bomb or an explosion. A tremendous fireball, flaming debris, pieces of the airplane, fuselage, landing gear, pieces of the building.

DEPUTY COMMISSIONER THOMAS FlTZPATRlCK FDNY

Various pieces of the plane were falling on the street. As we went down the street you could see parts of aircraft with stencil numbers on it and things like that. There was a wheel, or like a wheel housing or something else there in the street.

FIRE PATROLMAN PAUL CURRAN fuselage of plane on Vessey St


I parked the rig on Church right at Fulton, directly in front of the World Trade north plaza. My officer told us we're going to go into the north tower lobby. We proceeded down to Vesey. Walking down Vesey, we noticed large pieces of what looked like possibly the fuselage from the
plane. There was a caravan of motorcycle police coming up. We stopped them and we cleared the path of big O rings and pieces of fuselage of
the plane. We threw it to the side, and we told the guys to go on. They went up towards Church

BATTALION CHIEF BRIAN DIXON FDNY piece of a plane
I continued down Liberty, just west of 10 and 10. As I got down a little farther, there was what looked to be a piece of the cabin of the airplane, I guess. It looked like a piece of it about maybe six foot long. It looked like the windows.
WTC2 a boom, then blast of air, then black
I got just a little ways back and it was just like -- you hear the noise, a boom, and then a blast of air. It just kind of threw
me against the wall. That's where I decided to stay. Since it blew me there.

CAPTAIN RAY GOLDBACH
http://graphics8.nytimes.com/packages/pdf/nyregion/20050812_WTC_GRAPHIC/9110150.PDF
it was Dey or Cortlandt Street. We walked down
that block. It was littered with airplane parts,


ASSISTANT COMMISSIONER JAMES DRURY FDNY airplane debris

(Vessey & Church) You could see airplane parts on the ground and although I didn't realize it at the time, I later realized there were body parts, both on the concourse and on the street. (some of these might have been jumpers) I now made a left on Vesey and walked down
the street on the 7 World Trade Center side, where I could see more airplane debris

EMS CAPTAIN FRANK DAMATO

I parked my car on West Street, right around near, right about, right at the -- almost to the exit of where the Battery Tunnel empties out.
Then actually when I found my car, I found my car like later, later on in the day, but I left it there, because it was not able to be moved because it was covered. There was an airplane tire about 10 feet away from it.

FIREFIGHTER KENNETH ESCOFFRY FDNY WTC2


On the morning of September 11th about 8:45, I was relieved, and a few of us were standing in front of quarters when we noticed a plane came directly over the firehouse maybe around 8:45, somewhere around that time. One of the guys mentioned that the plane looked like it
was really low. Before we could really think of what he said, the next thing we heard an explosion. We saw smoke.


ASSISTANT COMMISSIONER STEPHEN GREGORY FDNY airplane was military type & green

I saw airplane parts on West Street. Q. How did you know they were airplane parts?
A. It looked like pieces of a plane, skin of a plane. I mean, they weren't really discernible. I couldn't say this was this part of a plane or that was that part. Just knowing a plane had hit the building and I looked and I saw it looked like the skin off a wing or a fuselage or wherever it came from. Q. Clearly not building material? A. No. The building material was sort of gray and you could see it, you know, how it differed from the plane. I was listening to the tape this morning of the people calling up and they were describing the
plane that hit the building. Actually, so many people saw it. They actually described the plane as it came in. They said it was a military-type plane and it was green and it was this. I mean, I never saw the color of the plane.
Several paragraphs blanked out

[Kevin Fenton]

20. Plane parts

(1) Not all the sections entered the building, for example the wingtips couldn't break the steel perimeter columns and some of the lighter parts would have been knocked backwards into the street in front of the entry hole.
(2) The plane exploded in the building and some parts could have been thrown backwards, out of the building, landing on the streets and buildings by the towers.
(3) One of the reasons the designers thought the towers would survive an aircraft impact was that a plane was supposed to pass through them (assuming it didn't hit the core) and come out the other side. Parts of landing gear and an engine (the starboard one from United 175) did actually travel through the towers and exit on the other side. The exit holes are visible in teh photographs.
(4) The green probably refers to the paint on the inside of the aircraft skin. I remember reading that all planes are green on the inner side of the skin or something like that - I have no idea why though.
(5) Most of the kerosene burnt up in the fires. There's a way of estimating how much fuel is present in a fireball (an equation based on the size of the fireball). 10-30% of fuel was used up in the exterior fireballs, plus another 10-15 percent in interior fireballs. That leaves more than half.

[spooked911]

9. Seriously-- is there ANY data supporting the idea that the core columns

were at a high enough temperature to significantly weaken them?

Or are they just assuming that the temperatures HAD to reach that temperature, because clearly the fires caused the collapse?

[Kevin Fenton]

10. Data

There is data supporting the idea the core columns were at a high enough temperature to significantly weaken them, although it comes from the computer simulation and is contradicted by the (few) surviving column segments. The computer simulation depends on (1) how well it was written (2) how accurate the data fed into it is. I guess the problem is with (2) - insulation stripped from 140,000 square feet of trusses (the equivalent of 3.5 whole floors) in the two towers, for example, is something of an overestimate IMHO. Also, it appears that many (if not all) of the of the other numbers NIST uses are, at least, on the high side.

[spooked911]

13. Right-- so there is no real data, only computer modeling that could

have been fudged any number of ways.

[pox americana]

14. Bingo. Welcome to the NISTle fudge factory.

This is all total baloney. First, that a plane crash would blow the insulation off of any floor trusses, and second, that it would make any difference.

[pox americana]

15. "an array of 0.3 inch diameter pellets travelling at 350 mph

stripped the insulation from steel bars like those used in the WTC trusses.” (117/171)

What makes anybody think a plane would disintegrate into "an array of 0.3 inch diameter pellets"? And how about the partitions, ceilings, furnishings and floors protecting the trusses and columns -- why aren't they part of the "experiment"?

[Kevin Fenton]

16. Experiments

It says they did experiments just before the quote you put in. I'd imagine that these experiments would be described in one of the subsidiary reports available at the website. I guess there might be some of pellets around 0.3 inches in diameter (along with other debris) after the plane exploded, but their ability to strip all the insulation from the entire east side of WTC 2, say, is open to question.