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RE: 97 UBC 1633.2.4 Deformation compatibility - is that a typo?

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Dennis, thank you for your thoughts.  You are too kind.

I would like to add that the first time I encountered an explanation of this
part of the new code was in a SEAONC seminar presentation by Ron Hamburger.
My explanation of drift derives mainly from memory of his description along
with careful consideration since that time.

I believe it was the Fall 1997 SEAONC seminar on the "Changes in the 1997
UBC" or some such title.  The accompanying paper by Ron is very
well-written, clear and concise.  Ron recounts the development of what is
now Chapter 16, Division IV, 1997 UBC, from the V=ZKCW and V=ZIKCSW days to
the present.  He explains the history and intent of nearly every aspect of
the seismic provisions such as base shear, R vs Rw, Ca and Cv vs Z, Ev,
period, rho, near-source, load combinations, collectors, omega, Fp, etc.
His explanation of rho is especially clear.

I probably should have consulted his paper before starting or joining the
most recent threads in which I have participated....

I highly recommend this paper.  Please don't ask me to fax it.  Perhaps the
SEAONC office will make additional copies available at nominal cost, or
perhaps it can be put on their website or this website somewhere.  Many such
papers are valuable tools.  All should be carefully read, as all have some
errors.  I hope this website can make some of these available in pdf format.

See,, and

Mark Swingle, SE
Oakland, CA


Dennis Wish wrote:

Mark, You have my most sincere appreciation. This is exactly what I needed
and I thank you so much for taking the time to respond and explain the code
is such detail. I only wish it were written as clearly as you explained it.
My feeling is that the Seismology Committee should take notice as to what
individuals like you do for the profession when you take responsibility for
what should come from the authors of the code. My sincerest appreciation for
your efforts

Dennis S. Wish PE