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RE: Philosophy: Seismic Design Standards

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Martin,
Thank you! This is the kind of interaction I was hoping for from Seismology.
I believe most of us on the list gain a better understanding of the issues
and goals of the policy makers when they are discussed in real time.

How does Vision 2000 play into the future of the code cycle? I read the
Vision 2000 section in the last Blue Book and gathered that performance
based engineering was the goal. It appeared to be justified once the mission
statement in the front of the code was changed to include prevention of
major structural damage.

Once we codified the idea of preventing structural damage without
quantifying the statement we create a potential for liability. "Major
Structural Damage" is, as far as I know, not defined in the code. Shouldn't
it be defined some place so as to mitigate possible liability?

Dennis S. Wish, PE

-----Original Message-----
From: Martin W. Johnson [mailto:MWJ(--nospam--at)eqe.com]
Sent: Thursday, January 20, 2000 9:54 AM
To: seaint(--nospam--at)seaint.org
Subject: RE: Philosophy: Seismic Design Standards





Although SEAOC has been actively working at developing a performance-based
design methodology, it has been presented as a separate appendix in the blue
book.  No one is even thinking about trying to marry it into the code at
present, it is really only a research excercise and perhaps a guideline for
engineers who may be involved in unusual or "new age" projects.  Before
anyone
thinks about putting it into the code we are going to have to come to grips
with
the liability aspects.  Engineers who promise a level of performance are
assuming a very significant responsibility, which is likely to include the
accuracy of design, quality of construction, the details of nonstructural
elements, and perhaps even the use and maintenance of the building years
after
it is built.  Heady stuff.

Future directions that ARE likely to occur include adding provisions for new
structural systems which offer good seismic performance (such as when the
EBF
system was added in the past), providing a more rational method for
designing
foundations for seismic effects, and improving the rationality of how the
structure actually resists the earthquake motions (such as by better
definition
of what an R factor is).  As an example, the seismology committee is
currently
(a) supporting an effort by a joint SEAONC and AISC group to develop a new
BRBF
system, (b) watching research work at UCSD for a new prestressed concrete
moment
frame system, and (c) working through an ad-hoc committee to research
foundation
design methods (such as the overturning concern that Frank McClure has often
mentioned).  This is in addition to watching and trying to support IBC,
NEHRP,
SAC, ACI and AISC development activities, keeping abreast of research
efforts
such as the CUREe program, and watching and trying to support membership
concerns such as are frequently voiced on this list server.

regards,
Martin