Comments by "Bo McGillacutty" (@Mrbfgray) on "CGTN"
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@_inveterate Glad you asked. As engineer who's made my living working w steel since late '70's, naturally I was fascinated by Twin collapses and studied it in detail.
First--melting steel, NO OFFENSE, is the rhetoric of ignorance, no reason to expect it. Load bearing capability of big structures may run as high as 3X higher than max expected load. (there was molten aircraft aluminum pouring out of side of one building at one point)
Steel loses essentially all it's strength at dull red hot, easily obtainable in your bbq, never mind how hot kerosene burns which is of course conditional, or what those numbers are. Fuel was the accelerant and didn't last too long, it was carpets, furniture, etc...roughly similar to a BBQ. This is why human occupied steel structures have thermal insulation on structural steel, to increase time heating to failure temps, allow time for escape, fighting it, etc.
The big surprise on 9/11 was how well Twins stood up to something they weren't remotely designed for. But sever, say 1/4 of ALL columns, all on one side ON IMPACT, then add heat to turn much of remainder crucial structure "plastic" and inevitably they fell.
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