Source: https://www.youtube.com/watch?v=u1CZmtR8gno&feature=youtu.be&t=21m21s (Skip to 21:21 if not auto-started there) This first post is the transcript, with minor asides omitted and some slides added for context. Discussion to follow. Mick: The NIST study, the ANSYS simulation came up with a set of damage that the fires did to the building, and you can see here these little black dots are what they refer to as being "Full Connection Damage" and these beams here, the red beams, are beams that have suffered significant damage themselves. So this is Column 79 over here. ... There's damage that is shown throughout the building. And when they took this pattern of damage from this simulation here, the ANSYS simulation, and then they applied it to this full height model, it caused a collapse. Mick: But it didn't actually use that particular connection that you just talked about [A2001 to C79] in this simulation. Tony: Oh sure, sure it did, sure it did. It had to. Mick: No, it didn't Tony: It had to Mick. Mick: But it didn't though. Tony: Well what did they use? Tell me that they used then Mick, because they say in Chapter 12 they use what they got from the ANSYS model. Mick: They did, they used that damage pattern. But that damage pattern didn't have that particular ... column connection failure, A2001 to column 79, That wasn't the first thing that actually failed. There was actually a number of simultaneous collapses. Mick: Which you can see here, there's collapses over here and over here [indicates the two circled areas above]. This say the "ANSYS-based damage application is resulting in floor structure failures around Column 79 to 81", which as you know is all the interior East side of the building, so they didn't actually..." Tony: Well where is that, ... they haven't told us that in the report. [Mick note: this IS from the report] Mick: It's quite apparent though, when the girder falls, Tony: you can't just show ... we want an analysis ... this is not an analysis Mick: If you look at this particular image here, which people are familiar with, the girder in question, A2001, I think is somewhere over here, it didn't actually fall down through the other floors. Tony: You need to justify, when you give a presentation like this, and you're making a claim, you have to justify it, you can't just say this is what we found, ... Mick: You were saying you found that some particular thing didn't happen earlier, I think if I did the same ... But this isn't really something that's actually up for debate really. We know that the ANSYS damage contained other connection failures. Tony: No, we don't know! They haven't released their data. Mick: well, look at this slide here: Mick: There's two areas in which collapse is happening simultaneously. Now this collapse over here toward the center of the building is completely separate from this collapse over here. Tony: Mick, if they left off the stiffeners which prevented the failure I showed earlier... Mick: No, I agree with that Tony... Tony: .. who's to say they might not have left off something here? Mick: Yes, they may well have done, but my point here is that you are focussing just on this one connection. And your analysis of that one connection is pretty good. Because it's quite comprehensive, and you did identify a number of things, like the stiffener plates that were missing, and the differences in the width of the plate, and other things like the amount of thermal expansion, things like that, it's all valid. And that's something that in that limited case does actually make a difference. But what we've got to look at is the actual global case. And when NIST did it they didn't use just that one collapse of that one girder. They used a large number of other collapses of other girders. Tony: I hear what you are saying. I saw you say this on the internet, okay, recently. But you have to be specific. You can't tell people we found some other areas where it collapses - well how did that happen? You have to show. They are not showing that. Mick: That's what came out of their simulation. Tony: Well, I want to see the results, the simulation is going to show the stresses ... [J.B. asks about missing data] Tony: I'm questioning why Mick supports it, if he doesn't have a basis of justification for supporting it. Mick: Right, well what I'm trying to explain to people is your criticism of the NIST report hinges around this on connection, the connection of girder A2001 to column 79, and the fact that you think it couldn't get off the seat, and if it did then it wouldn't damage the floors below. However, that's not what NIST are claiming in the global model. They claim that, they describe that as a possible initiating event, or a probably initiating event, because they did some simulations of just that one thing because it seemed like a likely thing. Tony: It's the main hypothesis Mick. Mick: Now, you've identified some problem with the simulation, and that's perfectly valid, that we should look at whether that's actually possible, if that girder did actually go off its seat or not. And it's possible that it did not. That is something that should be looked into. However that doesn't invalidate the entire study because the actual simulation that they used did not that as a necessary component.