Discussion in '9/11' started by Oystein, Jan 13, 2015.
If you think something is wrong, you need to explain why.
I believe you. I think it does look like that to you. I am comfortable enough with that.
Whereas you believe NIST's are great. We know.
Show me WHERE you think they are unrealistically constructed, and where you think they are unrealistically heated.
I believe he is telling the truth about what the results of his FEA are yes. You on the other hand, think it's wrong with zero to back that up.
I have been arguing that for years yes, as you have been arguing for years against it. It must be a bit of a blow to you, now that what I argued about the elements and omissions turned out to be correct, according to this study.
As for movement relative to the column, if the whole thing stays composite and moves together then that's what it does, yes. I am surprised by it, and I don't mind admitting that. I honestly expected less movement to the West, and am eager to see the conclusion of the project and more simulations to support that.
Of course it is. What else could it possibly be. One model reflects the drawings accurately (UAF) and the other does not (NIST). As you say above, you have argued that this does not make a difference since 2013 when I brought it to your attention on this forum.
If that is what it shows then yes. The movement of the girder wrt the seat/column should be expressed as 0, I agree. but it was expressed as a distance relative to the centre of stiffness.
If you have already contacted him about it then there is no point in me asking the same question. Why ask me to?
Perhaps it is better for me to make it clear to you again, and to anyone viewing this that I speak on my own behalf. Not for ae911, not for UAF, and certainly not for Dr Hulsey.
Sure my group spotted a load of errors in NIST's analysis, but the evidence level and the analysis at UAF is not something that I could be responsible for, but merely to have been part of a group that did find and push the issue. There's been many refinements and additions to our own findings on the way to the issue getting to this point.
Quick, straight question - who modelled the connection more accurately wrt the structural drawings UAF or NIST ?
I bet you can't bring yourself to answer it honestly. And remember the context is our thread of 3 or 4 years ago.
UAF included stiffener plates, and NIST did not, so in that regard it is more accurate.
Of course if nothing actually moved, then that point is irrelevant.
Because he has not replied (I used his UAF email address, do you have a better one?), and because his study is being misrepresented by the 9/11 Truth community. You're the best I can do in terms of a savvy apologist for the study.
So shouldn't that have been the main gist of the presentation? Zero possibility of any connection failure. Stiffener plate irrelevant?
And what about the 3 lateral support beams too, don't forget them. The floor system is the biggy here I would imagine. What do you think of the way that NIST accounted for composite action of the floor system with the steel ?
The analysis shows that even with NIST's own parameters applied that the girder would not fail though, and the stiffeners are part of that. It's incumbent on NIST now to release their data. To show their work. they would be well advised to do so before these base models are let loose on the world for anyone with SAP2000, ABAQUS or similar FEA programs to run simulations.
If I get a chance through anyone I contact to raise the issues I will, I think it's good to know what bits people find less easy to understand, and the relative movement point deserves to be clarified further.
The relevance of the plates was made fairly clear in the presentation, where NIST's values were applied to the model.
I have the same issues as I always have with NIST's model. No stiffener plates, no lateral supports to the North, and unrealistic values for movement due to expansion. (even trying to replicate NIST UAF could only get 5.1" west movement of the girder, NIST claimed 6.25", and even that would not fail the connection)
This question has already been answered multiple times. Please go back and read the thread.
I was referring to the ABAQUS model that UAF did. It is on page 43 of the pdf.
I though you were referring to the C79 connection. Obviously the 3 beams should have been included too.
Why don't you just explain what the evidence is that it was in error?
I tried that and was told that it was off topic because it is about NIST. Has that changed ?
You can describe if you can contrast it directly to what Hulsey did.
In the ANSYS NIST used CONTA178 contact elements between slab and beams/girders and USER105 break elements for shear studs. We don't know what values they used for friction in the contact element, as it is not discussed. They did not have shear studs on A2001.
Hulsey does not go into much detail regarding friction.
How many parameters/inputs do you have for these ?
We at least know that UAF has considered a range of friction levels between the elements to model the composite nature of the system over a range.
Why didn't they work out the actual friction level?
I cannot imagine that they didn't. But they bound the problem, which is the correct approach.
They were so much more accurate with the concrete too.
ADD - I recall Dr Hulsey also saying that even with no friction - ie totally non-composite - it still did not fail.
I await details with interest.
It won't fail Mick. You know this because with zero friction it did not fail.
Friction is not the only detail I'm waiting for.
Is the centre of stiffness the right place to state the amount of movement due to expansion from ?
I say it is. 100%.
Anyone here disagree Mick ?
Frankly, I have no idea what this "center of stiffness" idea IS, conceptually. Can you please define it, ideally citing a technical reference? And perhaps explain, briefly, how you would go about identifying the center of stiffness of simple structures like a segment of a fence, a bird cage, or just simply two different springs in series? It seems to me to be a made-up term.
Now to your question. I can't answer it without knowing what the term means, but your own "100%" answer seems to imply that you think it is completely false to state the amount of movement due to expansion in any other way then relative to a center of stiffness. Do I construe that right? Such that NIST made a conceptual error by not even mentioning cos?
This would imply that your own work on that connection as well as Tony's 2013ish was conceptually wrong, since you didn't state motion relative to cos.
What argument convinced you that cos is the 100% right way to do it? I think presenting an argument to support a claim is more valuable than doing a poll.
Not a concept that I was familiar with relevant to this either. Heard of it, as centre of rigidity before.
(above) + Lots of published papers showing examples of this. Centre of rigidity also refers to it.
I don't see an issue with performing sub simulations on particular areas. But it would come down to how these are applied, and I see the CoS issue as relevant to that. IOW the building will expand wrt the CoS.
Well they didn't mention their inputs either, but they surely had them.
I suppose it depends how much you want to trust an agency that gets 11" confused with 1ft when it's written on a structural drawing bill of material right in front of them.
No it wouldn't. We were checking the plausibility of NIST's hypothesis. Like with like. They were plain wrong. This has been proven for quite some time, but good to have that confirmed by the UAF study.
The fact that a beam pinned at one end will expand away from the pinned end. Pin the opposite end instead and the direction in which it will expand axially reverses. Always expanding with respect to the stiffest point.
ADD - how i am tending to think of it personally is this ( and this is my own personal way of thinking it out, so worth checking for error)
A 6 pointed star made up of I beams attached to a central hex shape. Heat it and the beams expand. They expand wrt the very centre of the hex shape. If you measure that from anywhere else you are on a bit steel that is moving, so dealing with 2 changes of position and not just one.
Apologies if that is maybe not the best way to think of it, or not the best way to explain it. But as I said, it's how I thought it through.
I should have added the "star" shape is lying flat on the ground and is entirely free.
Here is the CoS part from the presentation
And this is a also a great explanation of CoS and also CoM(ass)
The 2nd video is from NPTEL. Their channel is full of great lecture series.
Their channel is here https://www.youtube.com/channel/UCAVi5Zg6zSoyZUyKBtCJfmg
Funny, I was JUST imagining a simplest case to try to explain the problem, and I also came up with a sixfold object. Except I imagined a hexagon of I-beams, with a central point connected by I beams.
wait a minute... so he determined which way the whole building (floor, girder, column) moved in respect to what he determined from the colors, of that one timeframe moment, would be the thermal centroid?
Yes, it illustrates the issue that is solved by measuring relative movements of numerous objects from one centrally fixed point. Of course, it gets more complex in 3D and the example I gave is crude, yours is slightly better because it is fixed.
I have a few papers on it here written about real world buildings and mostly I am noting that - the CoS is not always the same for each floor, but it seems to be a good idea to try to get it close to the CoM.
Do you agree then that the CoS is the correct place to express movement in WTC7 elements relative to, when accounting for the whole building ?
its not close to CoM in your link above. http://debug.pi.gr/Default.aspx?ch=726
the studies i've read say in a fire situation the CoS moves. so in an 'uneven heating'/ 'thermal gradients' scenario it seems there is no "fixed" point.
So there would be more of a tendency for it to want to twist. I believe.
Can you link me to the source for that please.
sure. as soon as you link me to anything that back sup what you are saying.
just kidding. (kinda).. heres the latest one I was reading.
Yeah so this is about single elements (I beams) that are typically on the outside of a building being heated unevenly by way of their positioning. I don't actually think it is too relevant.
In what way do you believe it to relate to our WTC 7 issue ?
ADD - What is it you want a link to ?
You don't think elements in the building--including elements around column 79--were being heated unevenly as the fires progressed in different patterns around multiple contiguous floors? Do you imagine that the NE corner of the building was in an oven? I mean, that seems to be how Hulsey modeled it, but I didn't expect you would be trying so hard to defend his series of simplifying choices that take his model further away from reality after all the years you've spent criticizing NIST for choices that you believed did the same.
If you heat a metal structure evenly and slowly, it expands evenly, about the center
But if you heat it unevenly then some parts move more than others, say there's a fire under one girder, and just that one girder expands significantly.
When an individual girder expands that expansion will be resisted by whatever is holding the ends. In our simple example above the entire structure deforms. But in reality (and in the FEA simulations) there's three general things that might happen in our simple model, alone or in combination:
1) The entire structure deforms to accommodate the expansion, connections don't break
2) The connections deform. i.e either end might move relative to what it is connected to, this is things like the bolts being ripped out, fin holes stretching, sliding on a seat, welds breaking, top clip deforming, etc. This might just be a deformation, a partial failure (seat bolts bolts), or a total failure (walking off a seat)
3) The girder deforms, i.e it buckles to accommodate the expansion, leaving the end points the same.
Again, these things can happen in combination, and reality is more complicated than abstractions.
But really, thinking about the entire structure expanding around a center of stiffness is irrelevant. Our interest here is not how a shape deforms when evenly heated. It's how the individual connections and beams perform when the structure is irregularly heated.
Remember the three things above are gross simplifications to illustrate the point. The #2 (connections deform) is a potential type of failure, but the connection failure that generally gets discussed is a lot more complicated. You've got a girder (A2001) which has different connections at each end, then you've got a bunch of beams pushing up against that girder.
So here we've got to examine what happens to these beams as they expand. Will they buckle? Will they bend the girder as seen above? Will they bend the stiff outside wall out, and if so how much? What's the force on the bolts? Will the bolts shear at either end? Do the columns move at all? What's the force on the seat bolts at either end of the girder? What happens after the bolts break? What's the effect of the concrete slab and shear studs? Will the exterior wall spring back after the girder seat bolts break?
In theory a correctly configured simulation will answer these questions. In practice it's still an abstraction of reality, but still, it's going to give a lot better idea of the range of likely outcomes.
So what has Hulsey given us? Like NIST he's modeled the building on a few different levels. He's got different local models that end with the girder getting stuck against the flange, or just not moving far enough to walk off the seat, or with beams buckling because they can't move the girder.
But the real issue here isn't if that particular connection fails (it's possible it was not the first to fail). The issue is if there's a floor collapse leading to failure of column 79 (or maybe even 80). In that regards Hulsey only shows us a building floor smoothly expanding around it's center of stiffness.
No only does this make his earlier model irrelevant, it's also a ridiculous result, because it's showing us nothing about what actually is happening at the connection level. If everything is expanding smoothly there can be no connection failure, no beam buckling, nothing fails at all. The building simply bulges evenly a bit. That's not what happens.
NIST heated them evenly in their models.
No. Do you ?
NIST - no stiffener plates - UAF - Stiffener plates
NIST - NO lateral supports at North - UAF - included lateral supports
NIST - Movement relative to ???? - UAF movement relative to CoS
NIST - No data for friction - UAF - friction at varying degrees
NIST - NO shear studs on C44-79 girder - UAF - Shear studs on girder
Yes their models were surely different.
Which model do you consider to reflect the structural drawings available to both parties ?
No it doesn't. Unless it is equally stiff at either end.
Is that real world or abstract ?
Please cite from where in the NIST report you have come to understand that they heated the elements in their models evenly.
Re the rest, acknowledged on the stiffener plates, lateral supports on the north beam and sheer studs. Still an open question as to whether any of those omissions were material. Arup included them all and still saw girder failure. Only Hulsey using his clearly flawed heating model who has found them to have mattered so far.
And there is no mystery as to what NIST's measure of movement was (assuming we are talking about the 6"). Are you really going to pretend you don't understand that figure was talking about the south end of A2001 relative to its as-built location on the bearing seat on column 79?
It's in this thread. the ANSYS outputs being applied to the LS-DYNA model. Wasn't that actually a reply to you already ?
So we agree that UAF did a much better job of modelling the NE of the building, including the elements that were there on the drawings for both parties to see. Elements that NIST omitted. Thanks.
wow. that is one of the most obvious 'goalpost' moves I've ever seen. dude.
what does this have to do with all the holes in Husley's presentation? nothing.
What matters here is which of the analysis is more accurate, comparison is unavoidable.
You cannot claim a degree of inaccuracy with UAF without a comparison for a datum point.
We all agree that no FEA is perfect, but some are closer than others, and Dr Hulsey's is more accurate than NIST's, even Bentham conceded that point.
Which one do you trust? The more accurate one, or the less accurate one ?
The ANSYS connection damage was also applied to the LS-DYNA model. So several connection would have already have failed at the start of the LS-DYNA model, which was modelling the global collapse, not the initial connection failures.
The variable heading was in the 16 floor ANSYS model.
Depends on the connections. But what matters is what actually happens at the ends. Stiffness is just an abstract measurement.
Gravity for 2s, then damage I think, then temperature.
If the girder had not failed at column 79 the building would not have collapsed as per NIST. Which model did it fail in and lead to a progressive collapse ?
You can't compare that way. Just because they both possibly suck, in different ways, doesn't mean one is better than the other.
Husley completely neglected to model the actual events. The event is important, ergo: not good
Nist omitted some elements for whatever reason. IF these elements are important: not good.
Separate names with a comma.