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WTC7 and the girder walk-off between column 79 and 44

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gerrycan said:
This is absolute worse case scenario in terms of tolerances. In reality 2.5" would be closer, if not less. There is also another plate under the 12" seat which is wider onto which the girder would fall even if it could walk this far, which it can't.
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Was column 79 moved at all from it's original position? How about the effective length of the beam (I can't remember the number) that was pushing on it.

You seem to believe all these members remained in "as built" condition as the fires and expansion occurred.

I was in a building once that had a reasonable large fire. The building was deemed safe to enter but, after finding sheared off bolts on the floor we discovered that major floor beams were actually shortened by 4" due to being restrained when heated.

Your theory seems to be short sighted on the big picture.
 
gerrycan said:
So you are saying that a 'layman' should contact the people who have been described on this very page as being the best in the US, to point out their mistakes? aye ok.
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Yes, if in fact you believe yourself correct, you most certainly should.

It doesn't matter who you are, it matters what you say. If what you say is correct, and it is something that they have indeed missed, they will most likely revisit the issue with fresh eyes.

Anecdotal, but an engineer friend and I wrote a white paper a few years ago on the connection between arson and roof collapses, and made a calculation wrong. It was a pretty big mistake that changed the overall outcome of my conclusions.

One of my students found this mistake, and corrected me on it. I went back, wrote an addendum to my paper, and re-published it with the correction.

gerrycan said:
Which of these elements do you think would have not been present in the 'as built' drawings, and why?
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Well, the size of the flange could have been different for 100 different reasons. What they could be, I could only speculate.

Why don't you take these questions to the NIST, whom wrote the paper, and ask for their input?
 
gerrycan said:
Depends, how hot did it get? And NIST say that these beams were heated uniformly in their analysis, so their expansion would be proportional to their length. I know it's a crazy idea to think that these beams could all go to 600 deg in a few seconds and uniformly at that, but hey, that's NIST for ya.
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Actually it's not. Unless of course you can show me where NIST said this was the real world case. That's just how you have to build models.

You knew that though.

:rolleyes:
 
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gerrycan said:
Yes, foreknowledge is an issue, i agree.
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Foreknowledge of the collapse? You do realize that the firefighters at the scene made that call well before it collapsed, correct?

Would you like to expand on this at all?

gerrycan said:
Fire doesnt bring buildings like this down,
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Please show me the math supporting this. Fire has been causing the failure of steel for many years now. It's not a new concept.

gerrycan said:
and certainly not predictably, or to a countdown.
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Wait, what? Elaborate please.....
 
gerrycan said:
I'm just saying that the reason for the collapse is not the one that NIST claim because it is physically impossible,
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Please provide the math for that. I'll wait.

Show you work, and list any assumptions.

gerrycan said:
it follows then that this should be reinvestigated, in order to establish what could have caused this. Would it be reasonable for example, to expect NIST to test for explosives/residue, even if it were only to rule this out as a possible cause?
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Well, NIST could. However, this was already done by members of the NYPD, FBI, ATF, and many other local, state, and national police orginizations.

There is no evidence that anyone found physically at the scene, nor is there any video/audio evidence of any kind of explosive capable of cutting any of the core columns going off during the day.


gerrycan said:
After all, explosives have brought down way more steel buildings than fire ever has.
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Please back up this assertion with numbers and evidence. I'll wait....
 
gerrycan said:
We researched and produced the videos mentioned in this thread at the beginning. We will happily debate anyone who feels so compelled, real time, in an open forum, providing they are genuinley trying to get to the truth about this. There is more than just a 12" seat under this girder, even if it were possible, the girder would have to walk way more than 6" to get to a point where the bottom of it were unsupported, and also there has been no mention of the sideplates, which NIST also failed to take into account in their analysis. Further,look again at plate 'pg' it is underneath the 12" 'pf' plate and increases the required walk off almost by a factor of 2. I could go on and on......and maybe i will.
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I'm not following you. Can you explain why the sideplates and the pg plate underneath would force the girder "to walk way more than 6"" or "increase the required walk off almost by a factor of 2?"
 
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DGM said:
Actually it's not. Unless of course you can show me where NIST said this was the real world case. That's just how you have to build models.

You knew that though.

:rolleyes:
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ANSYS does allow for conductivity though doesnt it?
 
BasqueArch said:
I'm not following you. Can you explain why the sideplates and the pg plate underneath would force the girder "to walk way more than 6"" or "increase the required walk off almost by a factor of 2?"
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yes, it would make the distance reqiured more like 9.4". you can see it on frenkel 1091 on the bill of materials. The sideplates are a different issue.
 
gerrycan said:
yes, it would make the distance reqiured more like 9.4". you can see it on frenkel 1091 on the bill of materials. The sideplates are a different issue.
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Can you explain how the girder would have to be pushed 9.4" before it fell off? What pushes against what, etc. Can you take the push off step by step.
 
gerrycan said:
Yes, foreknowledge is an issue, i agree. Fire doesnt bring buildings like this down, and certainly not predictably, or to a countdown.
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Firefighters and the Red Cross are in on it.
 
BasqueArch said:
Can you explain how the girder would have to be pushed 9.4" before it fell off? What pushes against what, etc. Can you take the push off step by step.
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NIST say that the expansion of beams to the east of the girder caused the girder to walk off its seat. They thought the seat was 11" but it was 12". They did not account for the plate under the seat which was wider.
 
gerrycan said:
NIST say that the expansion of beams to the east of the girder caused the girder to walk off its seat. They thought the seat was 11" but it was 12". They did not account for the plate under the seat which was wider.
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Why does the plate under the seat matter for the extra "walk off distance" - of how many inches 9.4"?
 
BasqueArch said:
Why does the plate under the seat matter for the extra "walk off distance" - of how many inches 9.4"?
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maybe you should look at the drawing for yourself, and then say why you think it would or wouldnt change the walk off required.
 
gerrycan said:
maybe you should look at the drawing for yourself, and then say why you think it would or wouldnt change the walk off required.
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I know what the drawing looks like. You haven't explained your claim that this support plate would require the girder to be pushed 9.4" before falling off . Will you do so now.
 
gerrycan said:
This is absolute worse case scenario in terms of tolerances. In reality 2.5" would be closer, if not less. There is also another plate under the 12" seat which is wider onto which the girder would fall even if it could walk this far, which it can't.
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I don't see how you derived that tolerance stackup. NIST says the plate was 12", so the movement was 6". You say it's actually 5.5". Just using NIST, assuming they are wrong, the error is 0.5". So the expansion has 0.5" more to push the column. What is the tolerance stackup in the beam impacting the column, including the other end of the beam and it's attachment point? What if the column is deformed, will it still hold with only 0.5" left to go, and how close is that to the tolerance stack up, with the deformity?

You need to create a comprehensive model.

Before you do that, though, answer: What is the alternative to heat expansion to fire causing the collapse? Where is the model for that? Can you simulate it?
 
LSSBB said:
I don't see how you derived that tolerance stackup. NIST says the plate was 12", so the movement was 6". You say it's actually 5.5". Just using NIST, assuming they are wrong, the error is 0.5". So the expansion has 0.5" more to push the column. What is the tolerance stackup in the beam impacting the column, including the other end of the beam and it's attachment point? What if the column is deformed, will it still hold with only 0.5" left to go, and how close is that to the tolerance stack up, with the deformity?

You need to create a comprehensive model.

Before you do that, though, answer: What is the alternative to heat expansion to fire causing the collapse? Where is the model for that? Can you simulate it?
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I am concentrating on NISTs explanation here. I do agree that a better FEA model should be used though. As for the beam impacting the column, i dont understand where that is coming from. The beams are attached to the girder, not the column, and no one is claiming that the beams impacted the column at all. Are you confusing the girder with the beams? Also, you have things kind of the wrong way round. NIST said the plate was 11". Its a confusing topic, and easy to get the wrong way round.
 
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