LogFAQs > #944534945

F1areaGaman posted...

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...

No, they do not. That is the job of the fire engineer and the architect. Fire specifications for structural engineers follow prescriptive guidelines which are essentially specifying insulation thickness, minimum rebar cover, gypsum board, or some other insulation device. This is fine with zero thermodynamics, and it's based on a test developed in the late 1800s which has very little basis in how structures have been shown to behave in fire. If you're interested in a code that actually engineers around due look up the Eurocode. Note the actual AISC specification hadms essentially no information on steel behavior at elevated temperatures and the average structural engineer cannot tell you either the average temperature of a building fire or the temperature at which structural steel loses half its strength and stiffness.

Edit: If you're curious to know, specifications for insulation thickness to required fire rating mostly come from the ASTM E119 testing protocol, which establish fire ratings for various structural elements based either on deflection or internal temperature measurements as it gets exposed to the E119 heat curve (or E119 fire). It's important to note these tests ignore system level effects - i.e. it gets performance ratings for columns, beams, or slabs on their own but does not account for how slabs affect beams, beams affect columns, columns affect foundations, etc. That is essentially what structural engineering is, and it is not part of the design process unless you hire a specialist, and typically you only do that if you want to avoid fire proofing a certain element like an exposed column.

F1areaGaman posted...

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.

To put it frankly the amount of people who are qualified to even attempt this sort of analysis in the US is probably on the double digits. I'm sure the researchers at UoA did the best job they could within their realm of expertise. But rest assured, NIST is absolute center of structural material and systems research and regularly present cutting edge findings and experiments at structural engineering conferences. I can tell you from experience they are some of the most poorly attended sessions at NASCC and Structures Congress, despite being basically the only organization in the United States doing full scale fire loading tests of multi story building systems right now.

It is true that the information that's been released in regards to wtc7 is not nearly as comprehensive or accurate as the twin towers. This does not mean that wtc7 could not have come down due to a fire, which the UoA study claims. And the basis of that being true will more or less come down to the validity of the basic modeling assumptions. And NIST is essentially the center of all structural fire engineering in the world, employing the most distinguished and passionate researchers in the industry. It would take quite a lot to convince me that these researchers had more expertise than NIST, and quite a lot more to convince me the researchers employed now have been compromised to cover up a controlled demolition nanothermite conspiracy.

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