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Re: FW: More About 1997 UBC Fp

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

In the beginning was allowable stress simplicity.  Out of simplicity, ATC-3 was
created on strength basis.  ATC-3 (eventually) begat 1998 NEHRP.  1998 NEHRP
begat 1991 NEHRP.  1991 NEHRP begat 1994 NEHRP.  The 1994 NEHRP introduced the
F-sub-p factor based on location within building, with roof values being 4 times
that at grade.  The 1994 NEHRP begat 1997 UBC (sort of), ASCE 7-95 Chapter 9,
and 1997 NEHRP.  However the Provisions Update Committee for the 1997 NEHRP were
tempted by industrial interests and, at the last minute, changed the roof values
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 supplement.
The 2000 IBC will begat the 2001 IBC Supplement.

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

Rick Drake, SE
Fluor Daniel, Aliso Viejo


"La Count, Curt" <Curt.LaCount(--nospam--at)> on 09/16/99 01:37:00 PM

Please respond to seaint(--nospam--at)

To:   "'seaint'" <seaint(--nospam--at)>
cc:    (bcc: Rick Drake/AV/FD/FluorCorp)

Subject:  FW: More About 1997 UBC Fp

Thanks for your reply Rick.

 I understand that it is not possible to write a perfect code that leaves no
room for interpretation.  Engineers should be prepared to use engineering
judgment at all times, even when the code is clear about a particular item.
I was just curious about the evolution of the F sub p topic in relation to
the h sub x issue.  If this issue was first developed in the 1997 NEHRP
provisions (from NCEER), how did the UBC depart from the intent of the NEHRP
provisions?  Or was the 1997 UBC developed first and the NEHRP provisions
based on additional research?  This applies not only to the definition of h
sub x, but also the 3 coefficient (in lieu of 2)in equation 32-2?

Curt La Count
Jacobs Engineering
Portland, OR