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To: BwanaNdege

Seems I recall something about absence of asbestos in the WTC towers.

As far as construction materials and fire safety, though, the combination of concrete and steel was marketed as being almost fireproof and they were by comparison to wood framed structures butted side by side.

28 posted on 11/23/2012 1:49:23 PM PST by RegulatorCountry
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To: RegulatorCountry (see pages 3 & 4)

When exposed to fire wood retains its strength for a
longer period of time than metal. Unprotected metals
quickly lose their strength and collapse suddenly,
often with little warning. In contrast, wood loses
strength slowly and only as material is lost through
surface charring.
Average building fire temperatures range from
approximately 700º to 900º Celsius. Steel weakens
dramatically as its temperature climbs above 230ºC,
retaining only 10% of its strength at about 750ºC.
As a rule, wood will not ignite until it reaches a temperature
of around 250ºC. Once it catches fire, wood typically
develops char at the rate of 0.64mm per minute
under severe fire conditions. The char naturally insulates
the wood and raises the temperature level it can
withstand. Thus, in a 30-minute fire, only 19mm of
each exposed surface of the glulam is lost to charring,
leaving most of the original cross section intact. (see slide 4)

“Large wood members have greater resistance to fire than unprotected steel.
Steel, due to its high thermal conductivity, quickly heats up and loses strength during fires.

Large timbers are slow to absorb heat, slow to catch fire, and slow to burn.
The charred outer layer of a partially-burned timber insulates and protects the inner undamaged portion of the timber which retains the capacity to carry some load.”

37 posted on 11/23/2012 3:32:10 PM PST by BwanaNdege (Man has often lost his way, but modern man has lost his address - Gilbert K. Chesterton)
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