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Old 21st September 2011, 04:13 AM   #2898
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Originally Posted by tfk View Post
Dave, Chris,

My point was contrasting the survival of the thermally insulated steel columns to the failure of the uninsulated steel columns.

Reasoned extrapolations from this strongly suggest that:
a. if the principle supports for buildings are thermally insulated steel, they are highly likely to continue to support their loads in a similar fire.
b. if the principle supports for buildings are thermally uninsulated, then that building is in grave danger of collapse in a similar fire.
c. The Windsor Towers did not suffer total collapse precisely because its principle supports were not uninsulated steel, but reinforced concrete.
d. IF the principle supports of the Windsor Towers had been steel (like the WTC towers) that had been uninsulated due to maintenance (or plane impact or any other reason), then it is highly likely that the Windsor Towers would have totally collapsed just like the WTC buildings did.

One needs to be careful in comparing the performance of steel in reinforced concrete columns to its performance in pure steel columns. In the two cases, the steel is loaded completely differently (compression in steel columns but tension in reinforced concrete columns) and serves completely different functions (carries the loads in steel columns, but supports no external load in reinforced concrete columns).

With that caveat in place, it is true that the concrete forms a very effective thermal barrier for the steel when fires happen. Thereby allowing the steel to continue to perform its true function (making sure that the concrete stays loaded in compression where it is strong, and not in tension where it is weak).

Re Windsor Tower fire
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