1. gerrycan

    gerrycan Banned Banned

    [​IMG]
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    What's the difference? Those plates welded to the girder. They are called stiffeners.

    Why aren’t the stiffeners shown in the version above from the NIST report when they are shown in the actual WTC7 drawings?

    Why the stiffeners are so important:
    Stiffener plates are critically important. They allow a girder to transfer loads to a wider footprint (bearing surface) and increase its ability to resist failure.

    The stiffeners not only allow the load to be spread wider, but if the girder could shift (walk-off) as NIST alleges, they strengthen the web and bottom flanges. So if the girder web could somehow reach the edge of the 12” seat, the flanges would not fold under an offset load. NIST claims only 5.5” was necessary. They later revised this to 6.25”, but with the stiffeners the distance required would be approximately 10” before the girder could leave the seat.

    The stiffeners would make the type of failure that NIST supposed in their thermal expansion hypothesis completely impossible because the beams could not expand more than 4.75" no matter how hot they got. The reason the expansion is limited is because at just above 600C the beams shorten due to sagging more than they expand.

    The stiffener plates as shown in the WTC7 drawings were installed on the key girder that NIST claims initiated an unprecedented global progressive collapse of the building. NIST did not include them in their analysis.

    Thus if the girder can’t walk-off the seat it does not fall onto floor 12 and likewise floor 12 doesn’t collapse. The whole progressive collapse scenario evaporates without an initiating event. The stiffeners are the Achilles Heel of the NIST conclusion. They are truly the “game changers” described by mechanical engineer Tony Szamboti. Many other engineers agree. This walk-off is a pure, unadulterated fantasy.
     
    Last edited by a moderator: Nov 20, 2013
  2. Mick West

    Mick West Administrator Staff Member

    Even if it were impossible for the girder to walk off all by itself, neither of NISTS simulations of the building collapse sequence rely on this as a single point of failure. Multiple girders and beams actually failed, including the floor systems adjacent to, and above this girder.

    I know you don't like the simulations. But the idea this particular connection failed (at some point) actually comes from the simulations.

    So why do you ignore all the other failures?
     
  3. kawika

    kawika New Member

    If you study the SIMs and the reports at length you will soon discover that they are at odds with each other. The SIM shows the 14th floor falling into the 13th. The A2001 girder does not walk. It buckles in the middle. The NE floor system and the girder fall into F12 and stop.

    The narrative should have been created after the SIMs. After all the SIMs were necessary to help NIST understand what went on out of sight.

    Why don't they match?
     
  4. gerrycan

    gerrycan Banned Banned

    It is, I thought you had accepted this by now, you have been presented with the evidence for this elsewhere and have been unable to even come close to debunking it.
    But their explanation for the buildings collapse clearly does. Just because you can find a simulation output that also does not support this, it does not change that fact, and that is why you keep having to run to hypothetical models that you have no data for.
    In a model that you have no data for and that you cannot check or verify in any way, yes it does. On the other hand you have been presented with facts and figures that totally refute your stance, and are unable to debunk them. You need to counter facts and figures with the same level of evidence, not cartoons, because that's all these are until you can back them up with some data.
    And in order for that connection to fail NIST say repeatedly that thermal expansion of floor beams to the east of column 79 was the cause. An occurrence that has been proven to be impossible.
    Because they are based on alleged model outputs that you have no data for and cannot verify, other than stating that NIST have admitted that they were unable to model the connection detail properly. Why would you try to refute facts and figures with something that you know not to be accurate and that you also have no data whatsoever for?
     
  5. hiper

    hiper Active Member

    WTC 7 is gone Mick... its remains were not examined & were swiftly carted away. Combine this with the manner it disintegrated and the alledged cause of the total failure and it should tell a person all he or she needs to know.
     
    Last edited: Oct 13, 2013
  6. Mick West

    Mick West Administrator Staff Member

    The problem is you keep trying to reduce everything to this one simple thing, when the real situation was not simple.

    It does not seem like the girder would have been pushed far enough to the west for the east flange to fail, especially if there were stiffener plates.
    It DOES look like it was pushed quite a way, all the bolt would have failed at both ends, the attached beams were sagging, possibly the girder itself was starting to lose strength.
    It DOES look like many other girder, beam, and connections were badly damaged to the point of failure. Including above floor 13.
    It DOES look like some floor collapses were inevitable.

    So I'd be fine with you (provisionally) taking the girder walk-off out of the NIST narrative, and just going by what is left. Because all that seems to do is invalidate a point in the probable collapse sequence, meaning something slightly different is needed.
     
  7. gerrycan

    gerrycan Banned Banned

    You mean that I am focusing in on the very specific claims that NIST are making and debunking them one at a time, which is actually the way to approach this issue, very specifically and in a quantifiable way.
    So the girder would not fail and would in fact have continued to provide column 79 with lateral support.
    Given that unrestrained max shift it could do about 4.75" max, i think that "quite a way" is quite a stretch here. It cannot get pushed far enough to stop providing the column with lateral stability is the point.
    In the hypothetical simulation outputs that you have no data for maybe, yes. So, which connections are we talking about exactly here? Which beams and girders do you suppose look like they were 'badly damaged to the point of failure'? You can refer to E12/13 for the locations and specific call outs for the elements.
    What indicates this inevitability to you specifically? Do you know that the girders all have quite a thick mesh embedded into the floor system above them? Again, you need to be less general with these claims, otherwise they are just your opinions, with nothing at all to substantiate them, which i would guess, make them your guesses.
    Thanks for that. It's nice to know that accepted laws of physics and engineering are at least ok to apply to some parts of the building.

    What you have here is very general guesses as to what might have happened. Like the simulations that you refer to so often, these guesses that you keep making have absolutely nothing to back them up. You need to counter like with like. I would be happy to check out your claims if you just specify the elements and connections that you are talking about. You seem to be trying to play down the fact that the initiating event that NIST claimed has been proven to you to be an impossibility and moving onto other elements and connections as quickly as you can to avoid the issue of the connection. That's fine, but please be specific, so that your claims can be scrutinised.
     
  8. Mick West

    Mick West Administrator Staff Member

    There's no way of knowing exactly what happened inside the building, as there are too many variables. It's silly to present NIST's findings as the only possible things that could have happened, when they themselves only describe it as "probable". Lots of other things could have happened to initiate the floor collapse, so it seems quite a likely hypothesis.
     
  9. hiper

    hiper Active Member

    Wrong. Steel frame buildings are not susceptible to "lots of other things" that can initiate total structural failure.
    In fact there is only one thing they are susceptible to and that is controlled demolition.
     
  10. Mick West

    Mick West Administrator Staff Member

    Rather a broad claim. I was only talking of things that could initiate a floor collapse.
     
  11. hiper

    hiper Active Member

    A broad claim? The total structural integrity of WTC 7 was compromised.. that's why it totally collapsed.

    Even NIST couldn't find a way to ignore WTC 7 being in free fall for a period of time. Free fall means zero structural resistance and this can only point to one thing.
     
  12. Mick West

    Mick West Administrator Staff Member

    You are getting off topic. The issue here is if the presence or absence of those stiffener plates are entirely crucial to a local initiating event of flor collapse.

    What happens after the floor collapse it a different discussion. Please stick to the topic.
     
  13. gerrycan

    gerrycan Banned Banned

    Ok, give me a hypothetical for the initiation of floor collapse then, that does not involve failure of the C79-44 girder.
     
  14. Mick West

    Mick West Administrator Staff Member

    You mean "does not involve a simple walk-off to the west", because the girder is going to fail eventually.

    Let's say a failure of 79-80 and 80-81? on floors 13 and 14?
     

    Attached Files:

    Last edited: Nov 20, 2013
  15. gerrycan

    gerrycan Banned Banned

    Last edited by a moderator: Nov 20, 2013
  16. Mick West

    Mick West Administrator Staff Member

    Fire.

    Gerry, if you want to demonstrate you've eliminated all possible causes of collapse, then why don't you set up a site and list them all, and show how you eliminated them.
     
  17. gerrycan

    gerrycan Banned Banned

    I would rather deal with them one at a time, so what's yours?
     
  18. Mick West

    Mick West Administrator Staff Member

    But I'm not picking any one in particular, just that is seems very likely there's a range of possibilities.

    You claim the omission is "critical", so it's up to you to demonstrate it.
     
  19. gerrycan

    gerrycan Banned Banned

    I think that has been aptly demonstrated. Missing out elements and getting a thermal expansion calculation wrong is critical. You got the same equation correct once given the variables, why did NIST get it wrong?
     
  20. Mick West

    Mick West Administrator Staff Member

    Where did NIST get it wrong? Their most detailed simulation of the connection did not show that the girder was pushed off its seat to the west.

    So where exactly do you think they did a calculation, and got that calculation wrong?
     
  21. gerrycan

    gerrycan Banned Banned

    As you stated in one or your posts, they calculated that the girder had moved over 5.5 inches, this is wrong on 2 counts. It would not be halfway along the seat that they got the dimensions wrong for, and by your own reckoning would have been in excess of what the expanding beams would allow.
     
  22. Mick West

    Mick West Administrator Staff Member

    Did they calculate it? Where?
     
  23. gerrycan

    gerrycan Banned Banned

    If they didn't calculate it, then they must have just 'guessed' when they supposed that the girder moved 5.5". Is it reasonable to expect NIST to guess this kind of movement at the most critical part of the building in relation to their hypothesis? Bacuse if you can't find a calculation to back that up they might have. You have actually done the calculation yourself, taking the element dimensions from the drawings and the temperatures from NISTs own report. Can you remember what the maximum expansion in the beam was?
     
  24. Fires can cause steel structures to fail and thermal expansion and collapse can occur even without a fire.

    "Temperature Effect

    Space trusses are subject to thermal expansion and contraction due to changes in temperature and thus may be subject to axial loads if restrained. Potential temperature effect must be considered in the design especially the span is large." http://ktsadium.wordpress.com/
     
  25. Mick West

    Mick West Administrator Staff Member

    4 and a bit as I remember it. But my suggestion here is that NIST were just marking it as failed based on the simulations reporting it as failed. They did not explicitly do a calculation of that specific mode of failure you are suggesting is all-important.

    If I were debugging this, I'd make a 3D rendering of the floor system from the ANSYS model, and see exactly what it says happened.
     
  26. gerrycan

    gerrycan Banned Banned

    No, NIST clearly said that once the element had moved over 5.5" it was deemed to have failed. So again, they have assertions with no data, and when you do the math, they got it wrong. Critical error there.
     
  27. no, a point on the exterior was measured moving downward at a rate like "free fall" But we know the exterior was connected to the inside structure, so it wasn't freely falling.

    If I have 2 weights tied by a rope together on a table & I push one off the side of the table, it is not strange to think that the second weight might fall at a speed faster than free fall for a few seconds as the initial jerking motion of the first weight tied to the rope pulls on the second.

    I looked at "WTC7: NIST Finally Admits Freefall (Part I)" and David Chandler omits the start of the collapse! Note that his video says "Comments are disabled for this video." Chandler starts his measurement AFTER the collapse has already started. That isn't a minor point.

    "WTC 7's collapse, viewed from the exterior (most videos were taken from the north), did appear to fall almost uniformly as a single unit. This occurred because the interior failures that took place did not cause the exterior framing to fail until the final stages of the building collapse. The interior floor framing and columns collapsed downward & pulled away from the exterior frame. There were clues that internal damage was taking place, prior to the downward movement of the exterior frame..."


    NIST is answering this question: "IN A VIDEO, it appears that WTC 7 is descending in free fall ..." Those calculations are about THAT. "To further clarify the descent of the north face, NIST recorded the downward displacement of a point near the center of the roofline from first movement until the north face was no longer visible in the video." (The "free fall" you cite is about THAT video, NOT the total collapse sequence which actually starts with the penthouse.)
     
  28. Mick West

    Mick West Administrator Staff Member

    Bu that was not the only failure criteria in the model. In the LS-DYNA 47 model it appears to walk off axially after buckling when F14 falls on it. In the first model it does not walk off at all. In the ANSYS they say it failed, but don't give exact details.
     
  29. MikeC

    MikeC Closed Account

    Why is it a CRITICAL error?
     
  30. gerrycan

    gerrycan Banned Banned

    Seeing as we have no input data it is impossible to say how accurate these cartoons really are, but I think you have seen for yourself that they do not match with NISTs conclusions, and contradict each other as well.
     
  31. Mick West

    Mick West Administrator Staff Member

    So regardless of the stiffener plates, you'd disregard all of the NIST's simulation results then?
     
  32. gerrycan

    gerrycan Banned Banned

    They had the seat plate width wrong, and they missed out crucial elements on the connection. These would have increased the walk off distance required, so if they had been included in NISTs analysis, they would have had to try a new hypothesis, as they would have observed that this one would not initiate collapse as they stated in their report, and model descriptions.
     
  33. gerrycan

    gerrycan Banned Banned

    Until there is data to allow them to be checked yes. If they were going to introduce these in a court as being FEA output simulations, they would be required to produce the input data for them. If they did release the data their analysis could be checked fairly easily.
     
  34. Mick West

    Mick West Administrator Staff Member

    But I thought you thought it was all flawed regardless? Not enough detail?

    You've got the LSDYNA model without connections, can't you determine if there are any mistakes in that?

    Dimensional mistakes, omissions of parts, etc.
     
  35. gerrycan

    gerrycan Banned Banned

    How can you analyse something for which you have no data??
     
  36. Mick West

    Mick West Administrator Staff Member

    It has dimensional data, doesn't it? You can see if things are the right size.
     
  37. Mick West

    Mick West Administrator Staff Member

    Verify the precision of one set of data should give you an idea of how accurate they are in general. If you find an unreasonable amount of errors, it would be quite significant.
     
  38. gerrycan

    gerrycan Banned Banned

    The structural drawings are where I would go for dimensional data, not a model that by NISTs own words and your own conclusion does not replicate the building accurately.
     
  39. gerrycan

    gerrycan Banned Banned

    NIST said that they were unable to model accurately because of the target element size at the connections, so I need look no further than that to establish the lack of accuracy in the simulation. However, when one looks further into the simulations, they do not even match with each other, by your own admission.
     
  40. Mick West

    Mick West Administrator Staff Member

    That divergence shows the sensitivity of the models, and the error in insisting that there be one crucial make-or break event that the entire collapse hinges upon.

    The models really don't have enough level of detail for such precision. Only the first one comes close, and that's super limited in scope.

    Basically I think they were limited by time and budgets.