There's way, WAAY too much steel for such a weakening to even start being a remote possibility.
There's not NEARLY enough heat in those fires, and way too much ongoing dissipation.
Steel framed buildings stood after burning much hotter and much longer, plenty of times.
This meme is stupid and works against your credibility. Does steel have to melt to get weak? At what temperature does steel degrade below spec?
You have a LOT of homework to do, especially in physics.
That would have to include you. If steel loses 80% of its strength, all the structural margins are gone and collapse is the inevitable result.
There's way, WAAY too much steel for such a weakening to even start being a remote possibility. There's not NEARLY enough heat in those fires, and way too much ongoing dissipation.
Steel framed buildings stood after burning much hotter and much longer, plenty of times.
Unless youve done the math and can show us, your guess is as good as anyone elses.