Critical Errors and Omissions in WTC7 Report Uncovered
- Thread starter gerrycan
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Do you mean in the image on the left you can see what looks like the girder overhanging the seat (A)?
I think that's just a rendering issue. If you look at the seat below that you can see the brown column is visible through the back of the seat. (B) When viewed from above it seems more correct (C), but now the top clip is partially invisible (D)
No, but I see what you mean, could be rendering. I was talking about the plate that is at 90 degrees to the column face. This is where NIST are confusing column 79 with 81. Where you arrow "B" is pointing to.Do you mean in the image on the left you can see what looks like the girder overhanging the seat (A)?
I think that's just a rendering issue. If you look at the seat below that you can see the brown column is visible through the back of the seat. (B) When viewed from above it seems more correct (C), but now the top clip is partially invisible (D)
This is what the connection looks like on the structural drawings, viewed from the opposite side. If the illustration that you used was accurate, we would see the plate sticking out from the column in the same direction as the girder.
As you can see, the plate is not visible from the structural drawings. NIST have modeled the connection as 81, not 79, as they said in NCSTAR1-9, they took them to be similar. You can begin to see why now hopefully. What width do you think the plate was at 81?
As you can see, the plate is not visible from the structural drawings. NIST have modeled the connection as 81, not 79, as they said in NCSTAR1-9, they took them to be similar. You can begin to see why now hopefully. What width do you think the plate was at 81?
They explained why they did that.
There does seem to be some inconsistency though in NCSTAR 1-9A, where Figure 3-12 (which is Figure 12-24) describes it as "unstiffened". But the reasoning is explicit - they modeled it as stiffened, because they knew vertical failure of the seat would not happen. It's not clear, but likely with the limited resolution they needed to add this plate to make the seat behavior more realistic, based on the more detailed simulations.
Since vertical failure of the seat was not considered (Section 11.2.5), the connections at Columns 79 and 81 were both modeled as stiffened seats.
Please don't ask me questions to which you know the answer. It's a waste of time. Just say what it was.
First of all, do you see just how wrong they have got the connection detail?
^^^this is just so wrong on so many levels that i do not know where or if to start. Do not think i am being impolite because i am not. I can see how you would be so confused about this connection, NIST are contradicting themselves left right and centre here, so I can understand your confusion. What I cannot understand is your inability to recognise the obvious intent on their part to not be clear, and to present this information in such a confusing way.
It was 11". Which as you will remember is the seat width that they wrongly applied to plate 'pf' on column 79 and had to publish an erratum for, because they got caught out. This is where that "error" originated. I note you are now applying the description of 'stiffened' to connections in the same misleading was as they do in NCSTAR 1-9. They never modeled ANY of the connections as stiffened in the sense that they did not include stiffener plates.
"obvious intent"? I see normal human failings. Some poorly written of unclear parts of a report.
The thing is, we are talking about the global collapse model here. The connections had already been marked as failed in that model, based on the ANSYS model.
Again, do you see the huge error in figure 12-25 ? Where the connection below the girder is totally wrong?
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kawika
New Member
The top clip angle used in STC connection at Column 79 and Column 81 was weak in tension and needed
to be explicitly represented in the connection model.
The top clip angle needed to be explicitly represented, but the stiffeners didn't.
NIST has chosen to omit the stiffeners because they defeat their walk-off scenario.
They choose to use stiffeners on the seat in some drawings where stiffeners do not belong while they should be showing the stiffeners on the girder, but don't. This doesn't happen just once, but eight times.
https://www.metabunk.org/attachments/upload_2013-10-18_9-23-16-png.4522/
to be explicitly represented in the connection model.
The top clip angle needed to be explicitly represented, but the stiffeners didn't.
NIST has chosen to omit the stiffeners because they defeat their walk-off scenario.
They choose to use stiffeners on the seat in some drawings where stiffeners do not belong while they should be showing the stiffeners on the girder, but don't. This doesn't happen just once, but eight times.
https://www.metabunk.org/attachments/upload_2013-10-18_9-23-16-png.4522/
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You need to stop talking about models that don't resemble reality and start discussing the actual building,
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This thread is about errors and omissions. Surely any errors and omissions in the model are relevant? Where else could they have omitted the stiffener plates from? Where else could they have entered incorrect dimensions?
Models that you have no data for are not relevant really, because you cannot prove their veracity.
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Sorry gerry, you seem to be descending into personal attacks. I'm going to have to start applying the politeness policy and the posting guidelines. I can't ban jazzy and they let you get away with any kind of ad-hom you like. I've indicated the problem areas in your three posts above.
This thread is actually about the supposed conditions and temperatures that existed around the NE at floor 13 in WTC7, and their effects on the elements there. What NIST says happened to the elements is impossible, and has been proven to be so. Can you dispute this?
I can't dispute, based on the information you have presented, and assuming those diagrams reflect construction reality, that it looks impossible for that girder to have simply walked straight off that seat to the west. It thought that was clear. The debate has been over whether that is "critical" to the collapse of the floor system.
I would certainly be interested to hear what NIST has to say.
NIST have been asked. They refuse to comment. These omissions and errors are indeed critical to their hypothesis as has been clearly demonstrated here. Both they, and those who defend their position, have no response except silence because of the critical blow that these facts land on their erroneous report. Their models only serve to further expose their ineptitude.
No, their hypothesis was that column 79 became laterally unrestrained, and THEN buckled. It has been clearly demonstrated that the column would indeed have remained restrained due to the lack of failure proposed in NISTs analysis.
You have perhaps demonstrated it would not have become unrestrained starting with a walk-off of that particular girder in that way. You have not demonstrated there is no way it could have become unrestrained. NIST's analysis indicates that there would have been a lot of damage to connections and members.
NISTs analysis proposes that thermal expansion of the floor system was to blame for these failures. It is beyond doubt that they overestimated the extent to which this expansion occurred. In that sense they have demonstrated themselves to be incompetent at best and deceptive at worst. There has indeed been critical omissions and errors made in their report re the collapse of WTC7. Thanks for the debate though, interesting.
For clarity, here is their hypothesis in full:
They they did analysis that confirmed this hypothesis (or at least supported it), and formulated a probable collapse sequence.
8.2 LEADING COLLAPSE HYPOTHESIS FOR WTC 7
Based on observations and analyses of photographic and videographic records, critical study of the steel
framing, and simplified and detailed analyses to investigate possible failure modes that could lead to an
initiating event, the following leading collapse hypothesis was identified.
Initial Local Failure for Collapse Initiation
An initial local failure occurred at the lower floors (below Floor 14) of the building due to fire-induced
floor failures, leading to buckling of a critical column (the initiating event) which supported a large-span
floor bay with an area of about 200 m2 (2,000 ft2).
The leading hypothesis for the failure sequence that characterized the initial local failure was based on
fire-induced failure events in the tenant floors. Floor beams, girders, slabs, and connections heated more
quickly and to higher temperatures than the columns. Elevated temperatures in the floor elements led to
thermal expansion, with or without thermal weakening and sagging, which resulted in failure of floor
connections and/or buckling of floor beams. Sufficient floor component failures (connections and/or
beams) resulted in at least one unsupported column over multiple floors at the lower floors. This column
buckled and led to the initiation of global collapse.
Vertical Progression of Failure
Vertical progression of the initial local failure occurred up to the east penthouse, and as the large floor
bays became unable to redistribute the loads, this initial local failure brought down the interior structure
below the east penthouse.
Horizontal Progression of Failure
Triggered by damage due to the vertical failure below the east penthouse, the failure progressed
horizontally across the lower floors (in the region of Floors 5 and 7 that were much thicker and more
heavily reinforced than the rest of the floors), resulting in a progressive collapse of the entire structure.
Some of this was based on modelling, which some people find unacceptable, as the underlying data has not been released to the public.
Given the complexity of the modeled behavior, the global collapse analyses matched the observed
behavior reasonably well. The global collapse analyses confirmed the leading collapse hypothesis, which
was based on the available evidence.
The probable collapse sequence for WTC 7, based on the available data and evidence, and the
computer simulations
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kawika
New Member
Mick says: Would the presence of the stiffeners on the seats in the global collapse model make any difference? Failure of the seats was not considered either way, so what does it matter?
This is not about the seat. This is about the girder stiffeners.
The presence of the stiffener under the seat shown in a Figure labeled as C79 is an error. The omission of the stiffener plates on the girder at C79 is an error. How can you get an accurate model if you plug in the wrong elements and leave others out?
Yes, the seat was not failed. They couldn't justify a seat failure, so they went around the seat, by pushing the girder to the west. A brand new phenomenon-- Thermal Expansion.
The question is: Why can't NIST faithfully represent the actual conditions?
The seats were considered. The width of the C79 seat dictated the walk distance. First the seat was 11" (like at C81) and the walk distance only needed to be 5.5". Then the seat was 12", so the walk distance had to be 6.25". Neither value can be attained with the temperatures NIST reported.
There are other girders with stiffeners at other columns. They are scattered throughout the building. How could NIST get an accurate model without taking into account these very strong connections? How could they model any of the girders without the 2000 series drawings?
They modeled the connections, but they don't want to let us see exactly how they did this. We can't check their math. We are left with their inaccurate report and the accurate original drawings. When we see an obvious major omission why are there so many people willing to rationalize?
Mick, why are YOU so willing to rationalize for NIST? Can't you see that the whole report is built upon a foundation of errors?
This is not about the seat. This is about the girder stiffeners.
The presence of the stiffener under the seat shown in a Figure labeled as C79 is an error. The omission of the stiffener plates on the girder at C79 is an error. How can you get an accurate model if you plug in the wrong elements and leave others out?
Yes, the seat was not failed. They couldn't justify a seat failure, so they went around the seat, by pushing the girder to the west. A brand new phenomenon-- Thermal Expansion.
The question is: Why can't NIST faithfully represent the actual conditions?
The seats were considered. The width of the C79 seat dictated the walk distance. First the seat was 11" (like at C81) and the walk distance only needed to be 5.5". Then the seat was 12", so the walk distance had to be 6.25". Neither value can be attained with the temperatures NIST reported.
There are other girders with stiffeners at other columns. They are scattered throughout the building. How could NIST get an accurate model without taking into account these very strong connections? How could they model any of the girders without the 2000 series drawings?
They modeled the connections, but they don't want to let us see exactly how they did this. We can't check their math. We are left with their inaccurate report and the accurate original drawings. When we see an obvious major omission why are there so many people willing to rationalize?
Mick, why are YOU so willing to rationalize for NIST? Can't you see that the whole report is built upon a foundation of errors?
Yeah, and the plate detail is wrong. They modeled 79 as 81, this is a huge mistake, and one that you apparently don't consider 'crucial'. I do.
Then I asked you what difference it would make, and you told me the model was meaningless.
So why is it crucial?
It's crucial because it is the basis that allowed NIST to claim the seat was 11". It's crucial because they did not look closely at the column 79 connection and modeled it as a totally different thing. Even without the seat plate being 90degrees off, as kawika has said, they did not include any stiffener plates. If they HAD included the stiffener plates they could not have made the 5.5" (later 6.25") claim look remotely credible. It is crucial in every way to their analysis.
Hitstirrer
Active Member
79 cannot buckle unless the girder on floor 13 column 79 drops from its seat and starts a cascade. You have just admitted that the girder can't drop - ergo the collapse cant start - and then 79 cant buckle. Seems clear enough to me that the errors that have been found and make the girder drop impossible ( as admitted by you ) is indeed critical.
Nope. Nobody said that. NIST described that sequence of events in their "probable collapse sequence", but they did not say it was the only way it could happen, and their own simulations don't even show that sequence.
I thought that we were only going to use stuff that we could back up with data?
Hitstirrer
Active Member
lol. There you go again. When are you going to accept that the sims are a cartoon based on incorrect programming. The sims even disagree with their own report. And look nothing like real videos of reality. Of course the sims won't show that sequence. They are programmed differently. What do you think the words 'probable collapse sequence' mean ? After years of study that is the most probable - and that most probable sequence starts with that girder dropping.
And now that you have at last accepted that the girder can't drop- and cascade can't happen, and buckling cant happen - then that most probable sequence is now the least probable.
That means that gerry's proposition is correct.
Why not "a probable sequence".
But even if it's the most probably, and you've proven it wrong, what's the next most probable? And what after that?
Mick, I thought this thread was meant to be about uncovering critical omissions and errors in NISTs analysis, not about speculating.
Sure it is, but the errors you may have identified are only critical if they are the only possible sequence. So you'd need to establish that.
You are now asking me to prove a negative. It's getting silly now.
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