LogFAQs > #944521098

Jabodie posted...

There are actually a lot of important things I can touch on, but what fundamentally drives a lot of these engineer truthers is that "structures tip sideways when they collapse!" Which is generally true, but structural engineers tend to fall into intuitive fallacies and vastly overestimate what they know about structures (imo).

But very, very few structural engineers ever even think about fire, and certainly never have to consider it in a meaningful capacity in design. Fire codes are not highly influenced by evidence, and call for prescriptive measures rather than design or engineering.

I'm sorry, I don't believe you know what you're talking about. Structural engineers have strict fire hazard codes to abide by when designing a building. They think about fire A LOT. It's a huge safety issue on high rise buildings as escape is difficult. Maybe just "prescriptive" measures were taken into consideration in the 1800's but by the 1980s, when this building was built, fire codes were getting pretty advanced from what I understand. There's a reason what it was such a shock, as on TV just a few years earlier we watched crazy fires in giant buildings rage for hours and hours with no collapse...

Jabodie posted...

Simultaneous buckling can occur if there is a floor system is widely compromised, particularly in extreme heat where structural stability of the floor begins to transition from bending to catenary and tension field action. This is major contribution to the twin tower collapses.

The real lesson is that Building 7's collapse was not as thoroughly investigated, understood, or documented as the twin towers. Any simulations are going to be highly dependent on your modeling assumptions due to a lack of information. This is very true of even normal structural engineering, let alone incorporating highly sophisticated thermodynamics into finite element models. In structural engineering we like to say two things: 1) you can make a model say anything, and 2) all models are wrong, but some are useful.

That thought is especially important when you learn this project was funded by truther organization. It is important to know that, in general, structural engineers have a poor grasp of how high temperatures actually affect structural members, let alone structural systems. Earthquake simulations, for instance, are much better understood both as a numerical and practical problem, yet simulations results can vary significantly depending on a few key assumptions.

The entire reason America believes building 7 collapsed due to fire is because the 9/11 report's ONLY explanation was a computer simulation. And that simulation, as we can read from this study, was completely wrong and didn't even match the collapse at all. For example, the building fell at nearly the rate of free fall...we have evidence of that because it's on video collapsing. The study UoA did accounts for this. The 9/11 report does not. So i'm right there with you on how simulations can be useful or useless, depending. The 9/11 report did not release the parameters for their simulation. UoA clearly demonstrates what parameters they used and why.

Fire does not explain steel with oxidation and sulfidation. I mean that's hard evidence RIGHT THERE. Some FEMA worker put it aside and he probably wasn't even supposed because the rest of the evidence was promptly destroyed (for some reason they made that call instead of figuring out exactly what happened?)

I mean what's the other explanation for that? Somebody at work kept thermite in their locker?

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