'What about building 7'?

[pgimeno]

In your fantasy world, where that matters - how would the conclusion (Fire+Damage = Collapse) change if they reported those numbers correctly?

The point they fail to grasp is that the report's conclusions stand even if the numbers were wrong. Even CTBUH said that:

"The Council has several technical questions about details of the modeling; but we would not expect that to change the conclusions: that the floor beams failed due to fire, which led to buckling of the internal columns resulting in global failure."
​

 

[BasqueArch]

Ziggi
............The simulation showed that the floor beams could be heated to 600C, and if you plug that into NIST´s expansion equation, you end up with 5.5 inches of expansion plus change. At this point NIST had a valid input point for the computer model to report walk off, given the wrong 11 inch seat width and forgotten stiffener plates , and NIST could have clearly explained this in the report as I am asking for. ......

NIST never said the beams expanded more than 5.5" or 6.25". They said the beams pushed the girder off the seat.

 

[pgimeno]

Ziggi apparently keeps refusing to explain what his standard for "scientific proof" is, so I won't bother with him until he changes his mind, as demanding proof without saying what his standard is, when having already refused NIST's, is disingenuous. For the record, the report does satisfy my own standard.

So, in the meantime, here's a bump of message 4027 which gerrycan forgot to answer despite its crucial importance to the discussion. It basically shows that building 7 could indeed have fallen due to fire alone.

____________

The East displacement, if it did occur, happened AFTER the girder failed.

That's ridiculous. The expansion doesn't take an instant. It probably was still expanding when the girder walked off.

Anyway, are you then admitting that if it happened BEFORE, that would have enabled the girder to walk off due to displacement of the column?

Is that your position?

(To start with, you have no proof of your assertion, and yours is as good as mine that it happened BEFORE. But I want to be absolutely clear on that point.)

It's very important, because, well, let's assume for a second that you were right and that the displacement of the column started after the girder failed. In that case, the issue is just a matter of the order of things and the fire intensity at certain spots at certain times, but it would be basically proven that, regardless of whether NIST got it right or not, WTC7 could indeed collapse due to fire, and therefore your concern:

I am open to any explanation as to how wtc7 collapsed. As it stands there is not a reasonable explanation for how fire could initiate it and it remains therefore possible that it was brought down with explosives.

should no longer be a concern, and you have reasons to be happy. Also, since it wouldn't change the rest of the report in any way, NIST's conclusions would stand.

 

[Ziggi]

The title of Chapter 8 is "Initiating Event Hypothesis" so I would suggest that Chapter 8 has everything to do with "it." Specifically, section 8.8 says: "A finite element analysis of the northeast corner floor system was conducted to evaluate its response to elevated temperatures and to confirm which failure modes needed to be accounted for in the 16-story ANSYS model." Clearly, that would include girder walk-off, and clearly the description of walk-off at column 79 in this chapter is more detailed than the one in Chapter 11. I would suggest that it was the analysis in this section that provides the justification for the Chapter 11 general walk-off criterion of a beam or girder web being pushed to the edge of its seat plate. That would simply bring us back to the contention that the stiffener plates should have prevented web failure -- a supposition that has yet to be demonstrated.



Page 346 says: "The boundary conditions and the temperatures were selected to create maximum shear forces on the stud connectors and the beam and girder connections." That is consistent with the stated purpose of this particular model: to confirm which failure modes needed to be accounted for in the 16-story model, with respect to beam and girder connections. And in the 16-story model, no such boundary conditions or unheated slab were assumed, but it was found that the studs failed relatively early because of differential heating and relatively low resistance to shear. Therefore, the beam and girder behavior analyzed in Chapter 8 is not irrelevant.



The Chapter 8 analysis is based on thermal effects, which is consistent with its stated purpose, whereas the Chapter 11 is based on thermal effects over time as implied by the fire analysis. That is certainly not a justification for discounting the thermal effects shown in Chapter 8. I can't find anything in Chapter 8 that agrees with your characterization of "floor beams buckling so they pull the girder axally straight back to the westward direction" -- please provide a citation, since that doesn't seem to make sense. The "real walk off theory" in Chapter 11 is based on manually observing when a beam or girder was pushed half-way off its seat. While the text does indeed attribute that walk-off to the floor beams pushing the girder laterally westward, that is just a verbal description of the model behavior, which we know also included pushing column 79 eastward. If you believe that when the model was manually observed for the half-way walk-off criterion, only the westward movement of the girder was considered, then you must believe that they had some way of ignoring all other thermal effects that the model was reflecting. Please cite a reference for that belief.



And I could accuse you of blowing smoke, but that wouldn't advance the discussion, would it.

Chapter 8 introduces preliminary analysis used to develop the leading theory, which was the failure of the girder. It is based on an artificial scenario where several hours worth of heating are allowed to happen in about 1.5 seconds. The are other differences too.

The girder "rock off" that results from this experiment shows the floors beams buckling and pulling the girder back off the seat in the eastern direction, while the actual walk off theory in chapter 11 has the beams remaining rigid and pushing the beams forward and pushing the girder off the seat in the opposite western direction. There is absolutely no way to confuse these OPPOSING scenarios.

The walk off theory is based on the real fire simulation in chapter 10, which is completely different from the very articficial experiment in chapter 8.

The only result carried over from chapter 8 to chapter 11 is the failure of the sheer studs from the chapter 8 experiment.

Chapter 11 shows the final girder failure theory, and is titled "structural analysis of initial failure event"

Now try to get pgimeno to support your claim that chapter 8 shows the walk off event.

 

[Reactor drone]

The simulation showed that the floor beams could be heated to 600C, and if you plug that into NIST´s expansion equation, you end up with 5.5 inches of expansion plus change. At this point NIST had a valid input point for the computer model to report walk off, given the wrong 11 inch seat width and forgotten stiffener plates, and NIST could have clearly explained this in the report as I am asking for.

The fire simulation showed higher temperatures than 600°C. 600° was the temperature used in the initial assessment of the long span floor system near column 79.

 

[Ziggi]

Ziggi apparently keeps refusing to explain what his standard for "scientific proof" is, so I won't bother with him until he changes his mind, as demanding proof without saying what his standard is, when having already refused NIST's, is disingenuous. For the record, the report does satisfy my own standard....

Common Pgimeno, you are not seriously trying to tell people you do not understand what I say in post 4096 are you?

The most pertinent part is:

The simulation showed that the floor beams could be heated to 600C, and if you plug that into NIST´s expansion equation, you end up with 5.5 inches of expansion plus change. At this point NIST had a valid input point for the computer model to report walk off, given the wrong 11 inch seat width and forgotten stiffener plates, and NIST could have clearly explained this in the report as I am asking for.

At the beginning NIST was able to set the 5.5 inch displacement as an input in the model because it had a claim of 600C floor beam temperature, a known length of floor beams, known initial building temperature, and a known and listed expansion formula. When it entered the figures into the formula, it got the 5.5 inch expansion according to the scientific method.

But it could not apply those numbers because things changed.

What is needed:

1) calculations according to the same scientific method to show how it got the 6.25 inch number, and
2) structural analysis of the seated connection with the stiffener plates to prove that the flange would fold given the 6.25 inch displacement.

this is the most basic scientific requirement: data that lead to conclusion, not conclusion without data.

 

[Ziggi]

The fire simulation showed higher temperatures than 600°C. 600° was the temperature used in the initial assessment of the long span floor system near column 79.

No, chapter 10 limits the temperature of those particular floor beams to 600C, see Table 1 in ch10. Chapter 11 brings down that number to 400C.

 

[Reactor drone]

The girder "rock off" that results from this experiment shows the floors beams buckling and pulling the girder back off the seat in the eastern direction, while the actual walk off theory in chapter 11 has the beams remaining rigid and pushing the beams forward and pushing the girder off the seat in the opposite western direction. There is absolutely no way to confuse these OPPOSING scenarios.

Exactly where do they say that the 44-79 girder walked off in the western direction?

 

[LSSBB]

Common Pgimeno, you are not seriously trying to tell people you do not understand what I say in post 4096 are you?

The most pertinent part is:


At the beginning NIST was able to set the 5.5 inch displacement as an input in the model because it had a claim of 600C floor beam temperature, a known length of floor beams, known initial building temperature, and a known and listed expansion formula. When it entered the figures into the formula, it got the 5.5 inch expansion according to the scientific method.

But it could not apply those numbers because things changed.

What is needed:

1) calculations according to the same scientific method to show how it got the 6.25 inch number, and
2) structural analysis of the seated connection with the stiffener plates to prove that the flange would fold given the 6.25 inch displacement.

this is the most basic scientific requirement: data that lead to conclusion, not conclusion without data.

How many calculations are in an FEA?

 

[pgimeno]

Exactly where do they say that the 44-79 girder walked off in the western direction?

Page 527, top.

The girder between Columns 26 and 81 buckled and walked off the bearing seat between 3.25 h and 3.5 h. In a similar fashion, the girders between Columns 79 and 80 and Columns 80 and 81 buckled and the girder between Columns 44 and 79 buckled and walked off the bearing seat between 3.7 h and 4.0 h. Girder buckling was due to the combined effects of (1) gravity loads from the floor beams, (2) lateral westward displacement due to the thermal expansion in the east floor beams, and (3) increased axial loads due to thermal expansion in the girder.
​

 

[Grizzly Bear]

This alleged girder walk off is what starts the total collapse of whole building according to NIST, like tipping the first domino. If it does not walk off there is no collapse and NIST is back at the drawing board.

The building collapsed already. Regardless of the mechanism proposed by NIST. Do you believe the general conclusion that fire played a role in the collapse remains valid? And if so, is it your belief that the fires played a role differently than how NISTS conclusions played out?

You dont seem to be arguing for CD, so im interested in the am gle youre coming from here

 

[Reactor drone]

Page 527, top.

The girder between Columns 26 and 81 buckled and walked off the bearing seat between 3.25 h and 3.5 h. In a similar fashion, the girders between Columns 79 and 80 and Columns 80 and 81 buckled and the girder between Columns 44 and 79 buckled and walked off the bearing seat between 3.7 h and 4.0 h. Girder buckling was due to the combined effects of (1) gravity loads from the floor beams, (2) lateral westward displacement due to the thermal expansion in the east floor beams, and (3) increased axial loads due to thermal expansion in the girder.
​

That says the girder framing onto column 81 (the south side) failed that way. It doesn't say the girder between column 44 and 79 failed in that direction. Girder buckling was due to the lateral displacement to the west but the walk off direction isn't specified.

 

[Oystein]

Chapter 8 introduces preliminary analysis used to develop the leading theory, which was the failure of the girder. It is based on an artificial scenario where several hours worth of heating are allowed to happen in about 1.5 seconds. The are other differences too.

The girder "rock off" that results from this experiment shows the floors beams buckling and pulling the girder back off the seat in the eastern direction, while the actual walk off theory in chapter 11 has the beams remaining rigid and pushing the beams forward and pushing the girder off the seat in the opposite western direction. There is absolutely no way to confuse these OPPOSING scenarios.

The walk off theory is based on the real fire simulation in chapter 10, which is completely different from the very articficial experiment in chapter 8.

The only result carried over from chapter 8 to chapter 11 is the failure of the sheer studs from the chapter 8 experiment.

Chapter 11 shows the final girder failure theory, and is titled "structural analysis of initial failure event"
...

Thanks for this summary. It actually helped me to understand the NIST approach better. It appears to be a smart and valid approach.

 

[WilliamSeger]

Chapter 8 introduces preliminary analysis used to develop the leading theory, which was the failure of the girder. It is based on an artificial scenario where several hours worth of heating are allowed to happen in about 1.5 seconds. The are other differences too.

The girder "rock off" that results from this experiment shows the floors beams buckling and pulling the girder back off the seat in the eastern direction, while the actual walk off theory in chapter 11 has the beams remaining rigid and pushing the beams forward and pushing the girder off the seat in the opposite western direction. There is absolutely no way to confuse these OPPOSING scenarios.

Oh, now you're saying the floor beams pulled east instead of west, which is at least directionally consistent, but the reason I asked for a citation is that I cannot find any such description of the walk-off in Chapter 8. It also says the girder was pushed by the floor beams, so I'm afraid I'll need to ask again where you're getting that "opposing scenario."

The only result carried over from chapter 8 to chapter 11 is the failure of the sheer studs from the chapter 8 experiment.

(Edit to add) I also don't see any justification for that claim, if you could be so kind.

 

[BasqueArch]

Chapter 8 introduces preliminary analysis used to develop the leading theory, which was the failure of the girder. It is based on an artificial scenario where several hours worth of heating are allowed to happen in about 1.5 seconds. The are other differences too.

It's called FEA used by engineers with computers.

The girder "rock off" that results from this experiment shows the floors beams buckling and pulling the girder back off the seat in the eastern direction, while the actual walk off theory in chapter 11 has the beams remaining rigid and pushing the beams forward and pushing the girder off the seat in the opposite western direction. There is absolutely no way to confuse these OPPOSING scenarios.

You have managed to do it. The sagging beams were attached above the girder's centroid pulling the top to the east and pushing the bottom to the west, like this.

There's also a section (pp487,488) and Figure 11-19 in CH11 showing the same buckling and twisting of a girder or beam.

The walk off theory is based on the real fire simulation in chapter 10, which is completely different from the very articficial experiment in chapter 8.

The only result carried over from chapter 8 to chapter 11 is the failure of the sheer studs from the chapter 8 experiment.

Chapter 11 shows the final girder failure theory, and is titled "structural analysis of initial failure event"

Now try to get pgimeno to support your claim that chapter 8 shows the walk off event.

Sheer studs are gay guys dressed in chiffon.

 

[Animal]

Chapter 8 introduces preliminary analysis used to develop the leading theory, which was the failure of the girder. It is based on an artificial scenario where several hours worth of heating are allowed to happen in about 1.5 seconds. The are other differences too.

This in a nut shell demonstrates your complete ignorance of computer modelling. Better ask carpenter boy for help......at least he had the common sense to avoid that particular topic once he understood how foolish it made him look.

 

[JayUtah]

It's a good thing there no assumptions whatsoever in the controlled-demolition scenario.

 

[BasqueArch]

It's a good thing there no assumptions whatsoever in the controlled-demolition scenario.

And in their CD FEA they installed the explosives in 1.5 seconds.

 

[jaydeehess]

I outlined reasoning to support the idea that it was prior to walk off.
Your contention is that it occurred after walk off because NIST doesn't specify exactly when it occurred.


It would seem then that for you it must have occurred after walk off because that's when you want it to.

NIST mentions the column displacement because it is listing events that happened within the 4 hour mark, that´s all.

The problem for you is not that NIST does not specify exactly when the column displacement occurred, the problem for you is that NIST does not claim anywhere that this event aided the girder walk off, as you ASSUME. The 11.6 summary is there for a reason.

Did YOU not claim that the column displacement must have occurred after walk off?

 

[gerrycan]

The point they fail to grasp is that the report's conclusions stand even if the numbers were wrong. Even CTBUH said that:

"The Council has several technical questions about details of the modeling; but we would not expect that to change the conclusions: that the floor beams failed due to fire, which led to buckling of the internal columns resulting in global failure."
​

The CTBUH didn't think that the girder walk off theory was plausible either and made that quite clear.

The Council does not agree with the NIST statement that the failure was a result of the buckling of Column 79. We believe that the failure was a result of the collapse of the floor structure that led to loss of lateral restraint and then buckling of internal columns.

They go further than that though..

The report does not describe the detail failure mechanism of the girder connection to Column 79. Since this was critical to the failure we would expect to see diagrams of it, in its deflected, deformed shape immediately prior to collapse.

And as for the council's thoughts on the rock off theory.....

It is difficult to understand why the top bolts of the girder would fail at connection to Column 79

Don't forget also, that it was the CTBUH who asked NIST if end plates would have made a difference to their analysis if they had been present on the girder while the report was out for review.