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[AmerRescue(--nospam--at)aol.com]

In a message dated 10/26/2005 9:57:28 A.M. Atlantic Daylight Time, T.W.Allen(--nospam--at)cox.net writes:

Doug –

 

Thanks for your response, but I was looking more for a code interpretation rather than an opinion on behavior.

 

Regards,

 

T. William (Bill) Allen, S.E.

ALLEN DESIGNS

Consulting Structural Engineers

 

<snip>
The roof is normally the last part of a structure to fail and in 90% of building collapse the roof does not fail, at all. The higher you are in the building, the less weight above you...the less weight above you the smaller the applied force..the less the applied force the larger the voids..this is why bottom floors are squashed with 0-2% survivability and the top floors have 90% survivability.

 

This can vary if the frequency of the waves are more in tune with the top floors. This is a rare occurrence.

 

doug copp

Dear Bill:

 

I thought you might be interested in the practical results of the theory. Actually, behavior, in this instance is a minimal concern. If you are only concerned about the roof area. The people on the top floors survive regardless of their actions/behavior because their area hasn't collapsed.

 

The people on the bottom floor are usually killed regardless of their behavior because there are no voids large enough to survive inside of. The partial collapse floors are the areas where 'duck and cover' kills and 'triangle of life' enables survivability.

 

Regarding the technical considerations: You can predetermine the various forces which a particular point on a structural element can endure without failure but rarely can predict the forces that will actually be applied to the element or any particular point on that element.

 

All of this changes again when you consider the source type or the differences between hurricane, tornados, earthquakes and explosions.

 

doug copp