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RE: Philosophy: Seismic Design Standards

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I would suggest that the most productive thing that we could do would be to
try to put our codes on a more rational basis.  This would mean that the
emphasis would be on developing the theory and tools to validate the codes
and  to allow us to go beyond the proscriptive codes.

Such an approach would be compatible if not essectial to the implementation
of a general approach to performance based design.  In addition it would
provide a framework that would reduce the ambiguity in the code and it
would allow individuals to develop simplified approaches with confidence
that they were in compliance with the codes.

In other words for the same investment of time and energy we would have
more options.  On the other hand the current tendency to develope
prescriptive regulations that are applicable to only a limited number of
situations limit our options and often have unintended consequences.

I believe that the SAC Steel Project is a good first step in this direction
in that it has done much to rationalize our approach to the design of steel
connections.  In additions the research has provided engineers with many
insights into the perforance of materials that can be applied to other
situations.

One of the big payoffs of this empahsis would be in the improvement in our
ability to design for specific performance objectives thus allowing us to
better meet the needs of our clients and society.

Mark Gilligan


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Message text written by INTERNET:seaint(--nospam--at)seaint.org
> 
Introduction:

We are standing at an important crossroads in terms of seismic design
standards.  Nearly every important U.S. standard that affects
seismic-related portions of the design and construction of buildings (and
some other structures) has just completed a development cycle.  There is an
overwhelming consensus among those who are involved in the various aspects
of the process that now is the time to regroup and plan the near future
(perhaps 10 or more years) of seismic design standards in this country.  I
won't pretend to represent the parties involved.  However, many of the
participants in the formal process subscribe to this listservice.  I
believe
that your consideration and input may help to guide the process.

Many of the participants on this listservice could write volumes on this
topic.  However, I would suggest that you provide only a brief outline of
your fundamental philosophy on this topic; please don't provide a laundry
list of code items that need to be fixed.  Please keep in mind that the
underlying philosophy is the topic of this thread and that brief comments
are more likely to be read (and thus have a better chance of being
implemented).

Please comment on how you believe that things should be done.  Then, if you
believe that it is impossible for the code development process to achieve
this end, feel free to comment on what you feel must be done at a minimum.

================
Substance:

To what extent should seismic design standards:
a) Simply codify prevalent practice?
b) Codify current approaches with some improvements (i.e., be consistent
with current practice with some changes to address how things SHOULD be
done)?
c) Be founded on first principles (a "rigorous" approach) versus observed
performance (an "anecdotal" approach; recognizing that the two are not
always easily reconciled)?
d) Reflect the current state-of-the-art (recognizing that this can be a
rapidly moving target)?

I would suggest that several important items which affect the approach
taken
may include: applicability to geographically diverse moderate and high
seismic areas; evaluation and rehabilitation of existing structures versus
design of new structures; various sizes and styles of construction (from
residential wood frame to long-span or high-rise steel or concrete
construction); various levels of engineering sophistication; material- or
system-specific behavior; life safety versus economic recovery;
prescriptive
requirements in legally binding standards versus an outline of design
philosophy in voluntary guidelines.

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Michael Valley, P.E., S.E.                       E-mail: mtv(--nospam--at)skilling.com
Skilling Ward Magnusson Barkshire Inc.                  Tel:(206)292-1200
1301 Fifth Ave, #3200,  Seattle  WA 98101-2699          Fax:        -1201