Quote from 1000:
so whats the big deal, and why the Towers imploded?
Creep strain becomes important when the operating temperature exceeds 0.3 to 0.4 Tm (Tm is the melting point in degrees Kelvin).
At room temperature Creep in Metals is not significant for construction metals (however it is a problem for aluminum and lead)
Typically,
The melting point of iron is 1807K and 0.33 Tm is 602K (one third of meltin point). This is about 329 degrees centigrade.
it is belived that the length of time that the jet fuel was burning superheated the iron I beams to above 329 degrees centigrade.
That is what caused the implosion.
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Creep in Concrete
Concrete, believe it or not, also exhibits Creep.
Because of the complex constitution, creep in concrete is influnced by a lot of things such as:
1. cement content
2. water to cement ratio
3. cement type
4. environmental conditions such as humitity
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As an aside
The Great Ship Titanic also suffered a similar fate where the metalic propeties of the rivets used to bolt the ships haul were not known.
The ice waters of the Atlantic caused the rivets to become brittle, because of the nature of the Iron Carbon Steel alloy used.
The theory here is that tough materials absorb a lot of energy, and low toughneess (brittle) materials absorb little energy.
At sufficiently low temperatures, steel exhibits brittle failure (low toughness), and behaves like glass.
conclusion
Education is the key.
And as the saying goes, "Empty heads are the root of all Evil," which is what all the conspiracy theories are all about (basically a load of hog wash). [/B]
