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Originally Posted by Infinite_Loser
Here's something to think about. The engineers who worked on the WTC buildings in the early 70's over-specified the materials used. The core supports were made of high carbon indutrial steel which doesn't begin to weaken until exposed to temperatures in excess of 2500F for several hours. They even considered the possiblility of airplane collision. However, both towers collapsed within 90 minutes. It doesn't add up.
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Well that’s just flat wrong, as soon as steel reaches 2500F it is weaker, it does not magically get weaker soon after heating up, it gets weaker because it is heating up. Second the steel gets weaker much sooner then that, I’m not sure where you found your numbers, but try again.
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Originally Posted by http://www.popularmechanics.com/technology/military_law/1227842.html?page=4
"Steel loses about 50 percent of its strength at 1100°F," notes senior engineer Farid Alfawak-hiri of the American Institute of Steel Construction. "And at 1800° it is probably at less than 10 percent." NIST also believes that a great deal of the spray-on fireproofing insulation was likely knocked off the steel beams that were in the path of the crashing jets, leaving the metal more vulnerable to the heat.
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Furthermore, I can’t find any source that says the vertical structure was made from high carbon steel, can you please site a source. In my mind, a hard, ridged steel would be a bad choice for something that needs to sway in the wind.