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FW: FW: More About 1997 UBC Fp

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Thanks for the insight.  I know that code formulation is never pretty, and
slogging through it can sometimes be a thankless job, but our understanding
of the seismic forces on non-structural components and elements has advanced
thanks to your efforts.  It will never be perfect, but it is always helpful
for  engineers to have the opportunity to ask the experts.

Curt La Count
Jacobs Engineering
Portland, OR

From: Rick.Drake(--nospam--at)
To: seaint(--nospam--at)
Cc: 'seaint'
Subject: Re: FW: More About 1997 UBC Fp
Date: Thursday, September 16, 1999 2:33PM

With respect to F-sub-P and roof values:

In the beginning was allowable stress simplicity.  Out of simplicity, ATC-3
created on strength basis.  ATC-3 (eventually) begat 1998 NEHRP.  1998 NEHRP
begat 1991 NEHRP.  1991 NEHRP begat 1994 NEHRP.  The 1994 NEHRP introduced
F-sub-p factor based on location within building, with roof values being 4
that at grade.  The 1994 NEHRP begat 1997 UBC (sort of), ASCE 7-95 Chapter
and 1997 NEHRP.  However the Provisions Update Committee for the 1997 NEHRP
tempted by industrial interests and, at the last minute, changed the roof
from 4 to 3 times the grade values.  The 1997 NEHRP begat the 2000 IBC.  The
1997 UBC was not very sociable and begat nobody, not even a lousy
The 2000 IBC will begat the 2001 IBC Supplement.

Notice that not only is the roof value different between 1997 NEHRP (2000
and 1997 UBC, so are the R-sub-p values.

Rick Drake, SE
Fluor Daniel, Aliso Viejo