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Re: drift calculation, 1997 UBC using ASD

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Thanks for alerting me to the printing error.  BUT does the errata make sense?
If you compare Equations 12-6 (USD) and 12-10 (ASD), the USD equation will always
provide a larger drift.  The drift limit of 2-2.5%H is a constant dependent only
on building height. If the errata is correct then a building designed by ASD will
always be permitted to have more drift than when designed by USD.  Regardless of
the design method the drift used to compare to the maximum drift should be the
same.  The only way to do this is to use the USD load factors.

Incidentally, Appendix C (pg. 444) of the SEAOC Blue Book requires use of the USD
(1612.2) equations when the design is otherwise ASD.

Anybody got  ideas on this?

Bob Bossi



SDGSE(--nospam--at)aol.com wrote:

> In a message dated 11/10/99 3:10:55 PM Pacific Standard Time,
> rjbossi(--nospam--at)sonic.net writes:
>
> << Alex:
>  My code (1998 CBC, first printing) says:": ... the load combiations of
> 1612.2
>  shall be used."  1612.2 load combinations are USD and do not contain a 1.4
>  factor.  ie Eq 12-5 or 12-6.
>
>  Bob Bossi
>   >>
>  First errata to UBC97 changes the reference to 1612.2 to 1612.3, which means
> E/1.4 for drift calculations using ASD. It may not be the intention of the
> author, but there is also the Rho factor which got misinterpreted. You Loose
> some, you win some.
>