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RE: 2006 IBC vs 2003 NEHRP

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Scott,

Well said.  Another big benefit of having the NEHRP documents is the extensive commentary of FEMA 450-2 and the Seismic Examples of FEMA 451.

Thomas Hunt, S.E.
Fluor



"Scott Maxwell" <smaxwell(--nospam--at)umich.edu>
10/16/2007 02:41 PM
Please respond to seaint
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<seaint(--nospam--at)seaint.org>
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Subject
RE: 2006 IBC vs 2003 NEHRP





Nominally, ASCE 7-05 is the codified version of the 2003 NEHRP.  And I
believe that the 2006 IBC has gone to having most of the seismic provisions
be referenece provisions that point to ASCE 7-05.  I don't know for sure as
I have not gotten to getting a 2006 IBC as of yet.  There certainly can and
will be differences between ASCE 7-05 and the 2003 NEHRP, but overall they
should have the same "gist" and largely be the same other than maybe
language being more "mandatory" in nature in ASCE 7 than the NEHRP.
Basically, up until now, the NEHRP provisions have been the "precursor" to
the seismic provisions in the BOCA, SBC, and IBC code...much like the SEAOC
Bluebook was the precursor typically to the seismic provisions in the UBC.
You can think of things much like the relationship between the Bluebook and
the UBC.

In theory, I believe this will start to change some.  The NEHRP provisions
has two purposes in the eyes of the legislation that created them...1) a
place to create the "state of the art" in seismic design methods for the
country and 2) provide a minimum seismic design level for federal buildings.
In the past, both of these roles tends to play out in the same way...the
NEHRP provisions became a first "pass" of seismic code provisions to be used
across the country, just not usually completely in code language (i.e. not
completely in mandatory language).  This served the second purpose rather
well, but was not quite completely "state of the art" but more "state of the
art that is mainstream enough to be used in day to day design".  In
addition, the whole thing still had to go through the code development
process AFTER it had be through the NEHRP process.  It was not until last
half dozen years or so that a standards committee took up the seismic
provisions (in the form of the Seismic Task Group/Subcommittee of ASCE 7).
Once that committee came into full being, it became rather obvious that
there was some rather significant "overlap" in what NERHP and ASCE 7 Seismic
were doing (as well as a lot of overlap of people on both entities).  As a
result, I believe it was decided that the NEHRP process would stop doing
"code production" stuff and go back to what it was supposed to really
do...state of the art seismic design methodogly and theory.  Thus, in the
near future, the NEHRP, I believe, will NOT be the "precursor" to the
seismic provisions in the code, but rather much more "state of the art".
But, it will then also reference the latest ASCE 7 to fulfill the second
purpose (minimum design level for federal buildings).  This is because there
is no longer a "void" at the national level for create of seismic model code
provisions...ASCE 7 is now in place for that "role".

So, you should be able to get a 2003 NEHRP and get a real good feel for the
seismic provisions that will be required for the 2006 IBC.  In fact,
traditionally, the commentary for the NEHRP has basically been the
commentary for the seismic provisions of the IBC.  You should NOT, however,
substitute the 2003 NEHRP for the 2006 IBC for doing actual design that must
be per the 2006 IBC.  It is NOT a cheap way to get the 2006 IBC/ASCE 7-05.
There will be differences.  In fact, just getting ASCE 7-05 will not likely
be enough as the IBC process has a nasty habit of "tweaking" (i.e. adding or
modifying) provisions from the standards that it references.  It is
supposedly getting better, but it still done.  Thus, while I believe the
overwhelming majority of the seismic provisions of the 2006 IBC are
referenced in ASCE 7-05, there will still be at least a small part that is
NOT and is directly in the IBC.  Thus, you must, unfortunately, purchase an
ASCE 7-05 AND the 2006 IBC.

Regards,

Scott
Adrian, MI

-----Original Message-----
From: Mark Johnson [mailto:markajohn(--nospam--at)yahoo.com]
Sent: Tuesday, October 16, 2007 3:26 PM
To: seaint(--nospam--at)seaint.org
Subject: 2006 IBC vs 2003 NEHRP


How much difference is there between the 2003 NEHRP
provisions and the 2006 IBC?  There is a lot on the
web about the NEHRP provisions.

For other California engineers looking to update, I
noticed a webinar on the new code on Oct. 23 at:
http://www.iccsafe.org/training/webinar/102307SP06IBC.html

MJ


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