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RE: Lateral decision

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My 2 cents from a small private practice:

Ted Patrick, Plan Review Manager, City of Greensboro, NC, says:  "[for all]
retrofits/rehabs of any significant ... insist that the building be brought
up to code in its entirety." He explains, "if repairs are made to make a
building last another 50 years, the entire building should be brought up to
the level of safety of a new building designed to last 50 years."

Many engineers might believe that this ought to be public policy but it is
not.   No code that I know of takes such an approach.  Our society does not
want to bear the costs of requiring full upgrades to modern codes every time
a structure  is  remodelled, re-hab'd or upgraded (those costs are both
economic and to architectural character -- one assumes  that if Mr. Patrick
had his way as the building official for, say, Florence, Italy, the place
would by now look a lot more like, say, Greensboro, NC than the birthplace
of the Rennaissance).  In the real world, building officials are public
servants charged with enforcing building codes.  It is dangerous for any of
us, but particularly those in such positions, to mount a high horse and
pretend we are the white knights of structural safety, protecting the public
from its misguided desire to accept a certain level of risk.

Barry H. Welliver (private practitioner) agrees that: "If the lower level of
a two story is strengthened, perhaps the added new "stiffness" pushes load
further up the building and therefore may cause to second story to become
"unsafe".  He notes however that this effect, "may not in fact be a reality
all the time, and that doing something good downstairs is better than doing
nothing .... liability issue makes this a sticky .... We write code to help
remove risk for the public."


Certainly there is a possibility that if some engineer had designed an
upgrade of the
Northridge Meadows Apartment Complex to be implemented in 1993, closing off
some of those garage door openings or otherwise stiffening its weak first
floor, the shaking on the upper floors on January 17, 1994 might have been
more intense.  The owner might even have sued the hapless engineer, charging
that without the upgrade he wouldn't have had nearly so much drywall and
plaster cracking on the second and third levels.  And those thirty odd
people who probably wouldn't have died would never have thanked  the guy (or
gal).

I don't think we should let concern for our liability prevent us from doing
the
right thing, but I think Barry is on the right track.  I beg to disagree
however,
on why "we" write code.  The idea is to reduce risk, not remove it.

Ralph Kratz, writes:  "faced with an owner who wants to know how his
existing
building stands vis-a-vis earthquake safety ... do I tell him "all or
nothing?" ... It seems
to me that improving the lower story but not the upper story (of the church
mentioned
previously) would be preferable to doing nothing ... the San Francisco
building code (and perhaps others) has requirements for required ratio of
story strengths
in a partial upgrading that would seem to provide guidance in this
situation."


Ralph's thinking sounds sensible to me.  Of course you don't say all or
nothing.  You
try and help your client do the best they can with what they have within the
limits of the
applicable building codes.  In the case of a voluntary seismic upgrade, you
need to look at
the structure as a whole and try to identify its weakest links, then spend
the initial dollars to
strengthen them.  In a broad sense beyond the soft/weak story concept, each
change
will modify the behaviour of the system, which must then be re-considered in
order to
identify the new weak links where the next dollars will be spent, and so on
until the desired
performance goal is met or the client runs out of money.  IMHO it is foolish
to pretend that
the second constraint isn't going to control 90% of the time.

Drew Norman, S.E.
Drew A. Norman and Associates