NIST's Pellets

[rwguinn]

Gravy do you not think that the other sides, and the central cores would have to at least be heated above 250+ for a global collapse as fast as those to happen? One side is enough?

He finally got it!
We do NOT think that you have to heat the whole building--or "other sides, and the central cores".
Well done.

 

[jaydeehess]

Gravy do you not think that the other sides, and the central cores would have to at least be heated above 250+ for a global collapse as fast as those to happen? One side is enough?

Where do we see that only one side was heated?

I vote no, the insulation need not be removed from the entire structural member. then again you asked Gravy.(assuming he can decipher your questioning)

 

[Horatius]

For the two of you: We agree the NIST primarily blames the fire for weakening the steel, and initiating a global collapse due to bending trusses pulling the exterior columns inwards, don't we?

Seems mostly correct.

Do you agree that the fireproofing would have to be at least 50% dislodged throughout the floors at the impact zone, and throughout at least 5 floors above, for it to support a global collapse initiation thesis?

On this, I have no idea, and neither do you. What I do know is the experts who studied the question used what they considered to be a lower bound on the amount of lost insulation in their analysis. Do you know what a lower bound is? It's the best estimate they have of the absolutely smallest amount of lost insulation there would have been, based on knowing for sure that some was lost. Any errors or omissions in their analysis would therefore tend to work against the collapse initiation under these conditions, and so collapse would be more likely in reality.

They made very conservative assumptions, based on solid evidence and analysis, and still came to the conclusion that the fires were capable of starting a collapse.

Feel free to reject their numbers, analysis and conclusions, but until you can demonstrate that your numbers, analysis and conclusions are better than theirs, you're not going to convince anyone here.

 

[Yurebiz]

He finally got it!
We do NOT think that you have to heat the whole building--or "other sides, and the central cores".
Well done.

I never said the whole building. I'm trying my best to stay within the crash floors and floors above.

Seems mostly correct.




On this, I have no idea, and neither do you. What I do know is the experts who studied the question used what they considered to be a lower bound on the amount of lost insulation in their analysis. Do you know what a lower bound is? It's the best estimate they have of the absolutely smallest amount of lost insulation there would have been, based on knowing for sure that some was lost. Any errors or omissions in their analysis would therefore tend to work against the collapse initiation under these conditions, and so collapse would be more likely in reality.

They made very conservative assumptions, based on solid evidence and analysis, and still came to the conclusion that the fires were capable of starting a collapse.

Feel free to reject their numbers, analysis and conclusions, but until you can demonstrate that your numbers, analysis and conclusions are better than theirs, you're not going to convince anyone here.

Yes I agree I'm debating this on layman therms. What I meant with that question is, that for the collapse initiation to begin, roughly the majority of the trusses throught about 5 floors would have to bow in and pull the columns together, so the crushing wave can come from above and destroy everything as we saw it. The problem with that, as I see it, is because, although the floors were on fire as they claim it, I don't see how could the insulation be taken out sufficiently, so that the fires would heat up the steel along these floors so as to weaken, and start the collapse.

My view is, the NIST blames the fire; prove the fire can weaken non-insulated steel (while the insulated steel does not even lose 20% of it's strenght over about one hour, in a 1000C fire), but fail to account for how was it roughly removed from the trusses.

May I also point out that I'm not an expert to tell whether "one side is enough". I'm merely pointing out a discrepancy (as I see it) that has not been throughly debated here before.

 

[Horatius]

Gravy do you not think that the other sides, and the central cores would have to at least be heated above 250+ for a global collapse as fast as those to happen? One side is enough?

How would they be damaged, had the insulation not been dislodged? If it's only due to progressive load transfer, then stop blaming the fires then. The plane made a Huge gapping hole on roughly one whole side of the towers, plus a few core columns. That was probably enough to knock them down, then.

Here we have the fundamental problem. You can't discuss the impact damage and the fire damage individually. They both contributed to the collapse, and any attempt to separate their effects is both misguided and ultimately doomed to failure.

I've said it before and I'll say it again: This event was complicated. Attempts to "simplify" it are less than useful. There's a reason they used highly trained and experienced people to study it. If you're not one of those people, you'll be hard pressed to find any actual errors in their work. Most "problems" people will find will be a function of their own misunderstandings, and not errors in the report.

 

[Gravy]

Gravy do you not think that the other sides, and the central cores would have to at least be heated above 250+ for a global collapse as fast as those to happen?

I do not, because the engineers who studied these issues do not. Your arguments, like those of so many 9/11 CTs, are founded on personal incredulity. You haven't read the relevant material, but you don't believe that the collapses should have happened as they did, so you invent improbable scenarios to satisfy your lack of specific knowledge.

Please read the reports. Your imagination is not a substitute for engineering studies.

 

[Horatius]

Yes I agree I'm debating this on layman therms. What I meant with that question is, that for the collapse initiation to begin, roughly the majority of the trusses throught about 5 floors would have to bow in and pull the columns together, so the crushing wave can come from above and destroy everything as we saw it. The problem with that, as I see it, is because, although the floors were on fire as they claim it, I don't see how could the insulation be taken out sufficiently, so that the fires would heat up the steel along these floors so as to weaken, and start the collapse.

Where are you getting these numbers? If it's from your own assumptions, then that's the problem right there. Does NIST require the bowing across 5 floors? I've never seen anyone claim this.

And would the bowing have to be uniform across the entire floor? If you think so, you need to explain why.

 

[CurtC]

Do you agree that the fireproofing would have to be at least 50% dislodged throughout the floors at the impact zone, and throughout at least 5 floors above, for it to support a global collapse initiation thesis?

NIST did not agree with this. You quoted yourself, in your first post in this thread, that they explicitly do not make that assumption: "NIST
made the conservative assumption that insulation was removed only where direct debris impact occurred..."

Where did you pull the 5 floors above figure from?

 

[hellaeon]

My input is pretty weak but I would like to know what yurebiz thinks it would take to knock off the amount of fireproofing NIST claim is needed to handle enough fire to provide a grounds for collapse (and thats with LOWER BOUNDS).

Yurebiz why cant you accept what the experts say? Do you have any other reason then you dont understand? what makes you think this? any particular thing? You do know that debree was forcefully ejected threough the other side of the building, so why couldn't similar debree have enough force to remove fireproofing?

 

[Gravy]

May I also point out that I'm not an expert to tell whether "one side is enough". I'm merely pointing out a discrepancy (as I see it) that has not been throughly debated here before.

When you say "one side is enough," you're ignoring the fact that the buildings were damaged on more than one side, and in the center. The load that the damaged areas cannot carry must be taken up by other structural elements. That puts extra stress on areas that are badly weakened by fire, as in the photos of the south tower below.

ETA: I'm going to stop posting in this thread. It's a technical issue, and Yurebiz needs to read the reports rather than jumping to unfounded conclusions.
​

 

[DavidJames]

IYes I agree I'm debating this on layman therms.

I understand why you would want to keep the debate at the "laymen" level. CTist (not saying you are) want to keep it at that level because they are not qualified elevate it beyond that (but sadly that doesn't prevent them from reaching conclusions).

Does it seem odd to you that you've never read a detailed, thorough analysis refuting the NIST reports by a professional structural engineer, or have you? Now I've read CT documents about NIST, but they were not written by professional structural engineers and are not so much as refuting the details, as claiming NIST ignored what they believe are important details.

 

[jaydeehess]

That puts extra stress on areas that are badly weakened by fire, as in the photos of the south tower below.

[qimg]http://www.internationalskeptics.com/forums/imagehosting/thum_8790459973129bf48.jpg[/qimg]

ETA: I'm going to stop posting in this thread. It's a technical issue, and Yurebiz needs to read the reports rather than jumping to unfounded conclusions.
​

One can also note that the inward bowing observed in the north tower was on the opposite side from the impact. That is indeed where the fires were the worst in the north tower. So you have inward bowing and consequent loss of load carrying ability on one side and on the directly opposite side of the building you have severed perimeter columns and consequent lack of load bearing ability there as well. Added to this are a few severed and impact damaged core columns and fire further weakening the core columns that are still carrying any load.

Now if a core column is severed on one floor the load above that floor that that column was carrying is now distributed to other core columns, mostly to the columns most proximate to the severed one. Those columns in turn have had their SFRM abraded and thus are subject to weakening by heating BUT this need not be on the same floor that the column was severed. Fires on different floors affected different columns. In the north tower the loss of columns due to impact on one side and the inward bowing due to pull in of perimeter columns by sagging floor trusses caused the load usually carried by the perimeter to be largely transferred to the core via the hat truss. Essentially the perimeter was hanging from the hat truss. This added more and more load to the core as the perimeter columns were pulled inward and at the same time at least some core columns were being heated which meant that they would buckle putting more load on as yet unaffected columns. This continued until loads could no longer get distributed and a quick chain reaction of column failures resulted in the building collapseing

Now one can argue as much as one wants about whether or not fire could cause this sagging of the floor trusses. FACT is that there was inward bowing of the perimeter columns observed which became slowly more pronounced as time went on. This certainly could not have been accomplished by any fast acting method of causing a loss of structural strength such as explosives or thermite.

 

[WildCat]

That is from.. Page 80, final report 1-1
I don't know why the text didn't come out as well. Damn converter.

Perhaps that's why you failed to note that the time in those graphs is in seconds?

 

[gumboot]

I just want to point out that it was only the floor trusses inside the impact zone that have relevence in the impact-stripped steel-heat-collapse sequence.

We have photographic evidence of very poor insulation on the floor trusses.

It was these floor trusses that sagged due to heat and caused the collapse. Not the core columns. Not the exterior columns. Not any "beams". The spindly poorly insulated floor trusses. That's all.

-Gumboot

 

[Dave_46]

Sorry I missed this last night. I was watching my local football team (on television) get beaten in the semi-final of the league cup, and when I logged in afterwards my connection to the forum was a bit flaky, so I didn't reply then.

You all seem to have managed Ok, and I agree with the comment Gumboot made sbove.

I have assembled a general overview on Fire-Resistance testing, see below.

Dave

 

[Dave_46]

Some general comments regarding Fire-Resistance testing - I hope they are of use.

Assumption - I am going to be commenting on British practice. I assume American is similar.

In a fire resistance test, the test is conducted to a standard temperature/time curve. A standard fire is used to enable manufacturers to supply a product in the marketplace, and have a comparitive assessment of its performance. A "real" fire can be more or less severe than the standard fire. The nominal temperature of the standard fire in the UK test is given by

T = 20 + 345 (log(base 10) 8t + 1)

Where
T is temperature (deg C)
t is the time in minutes.

This gives a curve which passes through the following points.
Time Temperature
0 min - 20
5 min - 576
10 min - 678
30 min - 841
1 hour - 945
2 hour - 1049
4 hour - 1152

With regard to the quality of the applied coating, I would not expect that the site applied fire protection would have the same quality as the tested protection. When preparing specimens for test the manufacturer will ensure that it is applied as well as possible. When applied on site, by a contractor, not the manufacturer in all probability, it will be done to a price, so it is possible corners will be cut. This would not be a problem in practice, as the performance is going to be good enough that the protection doesn't fail too early in practice. The requirements of building codes are based on what happens to buildings in real fires, and I asume that in general failure is not too early (note, everthing fails eventually, if the fire lasts long enough).

A "real" fire would probably, in most cases, be less severe than the test fire, so a product could be expected to last longer than acheived by test. In the case of the WTC the fire was more severe than the test fire, so protection could be expected to fail earlier than the nominal time (this with intact fire protection).

 

[Gravy]

I said I was done here for now, but I do have a bit to add.

Assumption - I am going to be commenting on British practice. I assume American is similar.

Aside from the obvious fact that Dave is a Tory shill, he's made several instructive posts here about fire resistance testing and how CTs misuse the results of various tests.

In the case of the WTC the fire was more severe than the test fire, so protection could be expected to fail earlier than the nominal time (this with intact fire protection).

This quote from NIST's Shyam Sunder appears to support that statement.
[FONT=Arial, Helvetica, sans-serif][SIZE=-1]
[/SIZE][/FONT]

[SIZE=-1]The four laboratory tests provide only a means for evaluating the relative fire resistance rating of the floor systems under standard fire conditions and according to accepted test procedures. Shyam Sunder, lead investigator of the NIST WTC investigation, cautions, [/SIZE][FONT=Arial, Helvetica, sans-serif][SIZE=-1]“These tests alone cannot be used to determine the actual performance of the floor systems in the collapse of the WTC towers. However, they are already providing valuable insight into the role that the floors may have played in causing the inward bowing of the perimeter columns minutes before both buildings collapsed.”

[/SIZE][/FONT] [SIZE=-1]“The fire conditions in the towers on 9-11 were far more extreme than those to which floor systems in standard U.S. fire rating tests are subjected,” Sunder says.[/SIZE] (emphasis mine)

However, that comment was made in 2004, before the NIST investigation was complete. I don't believe the final report supports the claim that the tower fires themselves were more severe than the fires in the four floor assembly tests.

However, I can think of some major differences between the test assemblies and the actual floors in the collapse zones:

1) The test assemblies were undamaged.

2) The test assemblies had new, intact fire insulation applied to a uniform thickness.

3) The test assemblies were subjected to a constant, relatively even heat with even ventilation, rather than to a spreading fire with uneven ventilation that causes uneven heating and cooling of the steel.

4) The test spans were 17 feet and 35 feet, as opposed to the 60-foot spans in the areas of collapse initiation (South side of WTC 1 and east side of WTC 2). This was an area of concern, as Sunder notes:

One question raised by the data from the four tests is whether or not a fire rating based on the ASTM E119 performance of a 5-meter floor system is “scalable” to a larger floor system—such as the WTC towers assemblies that were 11-meter (35-feet) and 18-meter (60-feet) lengths. This was identified when one of the larger-scale tests in Canada had a lower fire resistance rating than the smaller-scale test in Illinois.

 

[Arkan_Wolfshade]

Some general comments regarding Fire-Resistance testing - I hope they are of use.

Assumption - I am going to be commenting on British practice. I assume American is similar.

In a fire resistance test, the test is conducted to a standard temperature/time curve. A standard fire is used to enable manufacturers to supply a product in the marketplace, and have a comparitive assessment of its performance. A "real" fire can be more or less severe than the standard fire. The nominal temperature of the standard fire in the UK test is given by

T = 20 + 345 (log(base 10) 8t + 1)

Where
T is temperature (deg C)
t is the time in minutes.

This gives a curve which passes through the following points.
Time Temperature
0 min - 20
5 min - 576
10 min - 678
30 min - 841
1 hour - 945
2 hour - 1049
4 hour - 1152

With regard to the quality of the applied coating, I would not expect that the site applied fire protection would have the same quality as the tested protection. When preparing specimens for test the manufacturer will ensure that it is applied as well as possible. When applied on site, by a contractor, not the manufacturer in all probability, it will be done to a price, so it is possible corners will be cut. This would not be a problem in practice, as the performance is going to be good enough that the protection doesn't fail too early in practice. The requirements of building codes are based on what happens to buildings in real fires, and I asume that in general failure is not too early (note, everthing fails eventually, if the fire lasts long enough).

A "real" fire would probably, in most cases, be less severe than the test fire, so a product could be expected to last longer than acheived by test. In the case of the WTC the fire was more severe than the test fire, so protection could be expected to fail earlier than the nominal time (this with intact fire protection).

Thanks much Dave_46! Input greatly appreciated!

 

[aggle-rithm]

If it didn't pierce through, and it then has only dislodged parts of the exterior columns of roughly one side of the tower, barely including any core clomuns at all, then how can it become a global collapse?

A global collapse as opposed to -- what? Did you think that only one half of the building should have collapsed, or do you think the moving portion should have toppled off instead of going straight down?

How were the fires which spread across the floors any relevant at all, if the many other steel beams did not have time to heat up above 250C?

If the intact steel beams were sufficient to hold up the upper section of the tower, then it wouldn't have collapsed. If they were not, then there is nothing to stop it from collapsing globally.

Why do I make this claim? Think about it: There are a number of columns that cannot support the weight of the upper portion of the towers because of damage, and a number of others that can. If the building is going to collapse, then there will be a point in time when the set of columns that were previously able to hold up the building are no longer able to do this. This is where the collapse would begin, NOT where the columns have already been compromised.

 

[Yurebiz]

Fine. My scenario is 100% wrong. I’ll take it. It wasn’t necessary for at least 5 floors to be at least 50% dislodged.

I promise I will read over key points of the NIST and quote them back here so we can all agree on a scenario, and debate the plausibility of it, OK? We know the NIST says the plane crash was the main factor at disabling fireproofing at the towers. So they must have an official scenario, right?

I was naïve enough to think that, had I assumed an erroneous scenario, you guys would come up and tell me exactly just what the heck is the NIST talking about, then. I was foolish to expect you to spoon-feed my rebuttal against you. I would do the same if I was on your side. I would say, “Go read the NIST”; which you’re right: I should read it thoroughly before making such a big accusation. I was hasty because this haven’t been opened as a thread before. I merely wanted to set things on a table before actually reading what you guys say about it, and what points might I have to look at the NIST. I’m sorry for having such a lousy approach.

I sort of expected you to lay back and refute, not my point, but my scenario (especially when I had read over it again, right after posting the 5 floors thing), and I’m sorry for failing you, but the point still stands

Fire may spread easily over many floors, but plane debris may not. While the NIST blames the fire for weakening and causing the bowing in of the trusses, it does not account for what dislodged the fireproofing out of it. Had fireproofing not been dislodged, the fires wouldn’t weaken the steel enough so that it would have significant loss of strength, above about 20%, in the given period of time.

All that is left, is for us to agree on what extend did the NIST assumed fires were, and where does it assume the insulation-dislodged steel frames were. Had they been far away from the plane crash, then there might be a problem there.

If we are able to agree on “how far is far away”, and “how dislodged is enough to heat it up”, and still come with an acceptable explanation for the scenario, we will then have successfully debunked this. Sounds hard, at least for me; And time consuming. I don’t get it how can you all put up with this sort of thing every day, you all must have motivations built in with reinforced concrete or something.

For now, I’ll just review what we agreed on so far; please point out if i have something wrong:

-The trusses at both Twin Towers most likely already had uneven SFRM spread across the trusses, and even missing insulation in a few, relatively short spots

-The trusses at both Twin Towers most likely did not suffer fires as strong and constant as in the tests.

-The NIST only assumed SFRM dislodgement where such claims can be proven by observation or analysis.

-There was enough energy in the plane crash alone to dislodge enough SFRM from trusses as to cause collapse. However, the amount of energy needed to get the plane debris (aka. pellets ) to reach the trusses in such a way to dislodge it. Many variables are contained within this factor, and some will probably remain unknown unless there's some piece of text within the NIST which successfully analyzes all this. this will remain unset until someone posts something, or I get to work and search for it myself.

-How much dislodgement, and where, was it necessary to support the Towers's global collapse, (as explained by bending of trusses due to fires+dislodgement, pulling in perimeter columns) is still not set. This is the crucial information in which I screwed up in speculating earlier, but it is still not set. I'll probably have to do this on my own, I suppose.

Feel free to contest all the above. I probably won't answer today if it involves deep thinking, as I had enough thinking, for now.