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Re: Need feedback from those using strict interpretation forWoodstructures

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I knew that!!  I was just testing to see if anyone
was listening!! :)

Thanks for keeping me straight.  I really did know
that, I just got sloppy.



FEMCCLURE(--nospam--at) wrote:
> Lynn Howard,
> In the subject email message, "Need feedback from those using strict
> interpretations for Woodstructures, you stated: "We are supposed to be
> designing for the earthquake that has a 10% chance of reoccurring every 50
> years."
> According to the 1997 UBC, Division IV-Earthquake Design, the correct
> definition of the "Design Basis Ground Motion is that ground motion that has
> a 10% chance of being exceeded in 50 years as determined by a site-specific
> hazard analysis or may be determined from a hazard map."   This Design Basis
> Ground Motion has a MEAN RETURN PERIOD of 475 year with a mean annual
> probability of exceedance of .002 or .2%.  There is nothing in this
> definition that addresses the question of the recurrence time for the design
> basis ground motion.
> Earthquakes are defined by their probability of being exceeded in a certain
> number  of years or their MEAN RETURN PERIOD, not their chance of recurrence
> in so many years or their recurrence period like the time for the return of
> Haley's comet.
> Frank E. McClure      FEMCCLURE(--nospam--at)    July 31, 1999.