Need a book? Engineering books recommendations...

Return to index: [Subject] [Thread] [Date] [Author]

RE: California Earthquake Problems

[Subject Prev][Subject Next][Thread Prev][Thread Next]
I came into this thread late - picking up on the post 1933 code changes
which are believed to include residential homes.

I went back to read the article that Yank2000 reprinted. As with most things
I read, I try to stay open minded and to put the articles into proper

I read Ken Tarlow's response which suggested or implied that he did not take
the warning seriously because his home was unscathed by the higher magnitude
quakes in the state. This is a typical response of homeowners who feel that
the warnings are based upon unsubstantiated fears since they are still only

I believe that there is a serious concern with potential damage caused by
poor performance of conventionally framed homes in larger magnitude quakes.
But historically, wood framed homes have performed better than expected and
those of greatest risk have been identified (i.e., cripple wall and
anchorage inadequacies).

I would issue the same response to Ken's comments as I do to most of my
clients (and contractors) who have little faith in engineers - the
conditions required for this type of predicted damage to occur must be just
right. This saved hundreds of unreinforced masonry buildings in Santa Monica
from damage which dated from the turn of the century (the last turn) to
January 17, 1994 when the conditions for damage turned favorable.

With that said, I have a problem with any prediction intended to overdesign
a structure. As any bean-counter knows, there is a point where the economics
of the structure prevent extreme retrofit or increased code standards. This
is the motivation for performance based engineering - an idea that I support
(with a few reservations).

We live in a society where aesthetics rules over common sense. I live in a
resort area (Palm Springs) which has a winter population that doubles the
summer permanent population. Many of these visitors invest in winter homes
within gated communities and beautiful golf courses. The majority would
prefer to live in glass houses and argue vehemently if you try to take away
even 18-inches of their mountain or golf-course view. They are also fearful
of the renown California earthquakes, but not afraid enough to compromise
their desires. This poses a couple of issues:

Even if the home is engineered, who should be responsible for the extent of
damage when the engineer can design only to code (considering the
competition in the field which compares the economics of the design)and the
owner or designer demands a structure without regard to engineering
judgement that will predictably perform in a manner to increase the
potential for damage and yet protect lives?
In other words - should the insurance carrier or the State plan be liable
for damage on creative designs which might not perform as well as a more
conventional plan? Excessive insurance payouts are reflected in our
pocketbooks by increased premiums. Therefore, should the average insured in
the pool be penalized for damage settlements on homes owned by those who
want to maintain aesthetics that push the line of professional judgement.

I am sure that most of us have been interviewed by clients who want the code
minimum, clients who think that structural engineering is a market created
to line our pockets and which has no right to interfere with the decisions
that can be made by architects, or that engineers are simply committed to
over-design and conservativeness. Having to defend our profession is a daily
part of our practices when dealing with the general public and

Finally, what is the economic limit to design to and if we adopt a
performance based design code, should the Insurance company have a sliding
scale of premium rates to compensate? And, should the insurance company be
able to deny coverage to homes that they evaluate to be a higher risk?

Dennis Wish PE