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Old 3rd March 2006, 07:49 AM   #13
rwguinn
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Originally Posted by LTC8K6 View Post
You only need about 800-1,000F to weaken the steel appreciably. The jet fuel was quite enough, anything else such as carpets and furniture just sped things along.
This is true.
At 600 degrees F, steel (generally) retains 95% of its room temperature ultimate strength. At 800 degrees, its at 88%, 1000 degrees, 58%, and at 1200 degrees, you're down to 37% of Ultimate (breaking) strength after 1/2 hour exposure.
Yield strengths are even lower--and once you start bending (or buckling, which in this case is the more likely scenario), things progress rapidly, since the geometry of the collumns is a large portion of their strength. Distort the geometry, and destroy the strength.
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