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Re: '97 UBC Design - Are you too old to change your ways???

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To all who were thoughtful enough to write and to all who are listening:

Pleae read my messsage again.  I does not suggest that the 97 UBC is the
answer to the Northridge problem.  It only argues that earthquake engineering
is an emerging technolgy, that the cost of Northridge damage is said to be
unaccepably high, that it is largely due to residential construction, and
that we need to embrace change.

If you have ever heard me speak, you know that I agree whole heartedly that
we, as structural engineers, are doing our job. Our modern buildings,
designed and constructed properly are performing in a life safe manner. BUT,
that is not the issue.  The issue is that the cost to fully restore our
communities is too high. Many people think that all we have to do is make the
structural code tougher.  But we (the designers) all know that only solves
part of the problem. The other part, the most expensive part, we do not deal
with and neither does anybody else. That is where the change is needed, and
we need to take the lead.  Nobody else knows what to do but us.  We need to
make a clear statement about what we are doing, publically state that our
designs do not prevent very costly non-structural damage and then listen to
the public about what they really need.  I think we are in for a surprise.

Do you realize that most people think that the stingent structural provisions
of the code are going to prevent major loss in the next earthquake?  Do you
know that the UBC does not clearly dispute this expectation?

Chris Poland

ps:  Check the roster of the code writers.  You will find a lot of practicing
structural engineeers who care enough to volunteer.

r nester wrote:

> It is commonly reported that of the 20 billion in damage caused by the
> >Northridge
> >earthquake, 15 billion was in residential construction.  Add to that
> >the fact
> >that most of it was relatively new and we  have a justification for
> >change.  The
> >Caltech/Curee rpoject on wood frame construction is a testamony to the
> >need for
> >change.  I believe that the new provisions in the 97 UBC are in part
> >related to
> >this experience.
>
> I see this line of thinking as a weak, overly simplified  straw man
> arguement.  Of the $15B, how much was non-structural damage unrelated to
> structural strength?  How much was due to water damage, soil movements,
> secondary fires, loss of use, temporary housing, and code-driven
> upgrades?  Of the structural damage, what portion was for homes designed
> and built before 1976?  How did homes built to the 1988-91 UBC's fare in
> relation to others?  The overwhelming majority of structures and enclosed
> space in the San Fernando Valley are residential.  Whatare the damage
> costs relative to replacement costs, broken down into foundation,
> structural, non-structural, and into structure types.   Without this
> data, we are all just shooting in the dark.
>
> The 1988 UBC was the ultimate result of ATC 3-6, published in 1976-78,
> with a detailed commentary.  That commentary compiles statistical
> arguements for adoption of the ATC provisions based on a statistically
> low, but presumably acceptable probability of structural failure.  It
> also compiles similar statistics for the probability of life losses and
> injury.   It was an attempt to bring the statistical probability of
> seismic failures to the same level as for wind or other natural hazards.
>
> Using the ATC 3-6 Commentary statistics, a 30% increase in design base
> shear, coupled with the other engineering provisions of that (proposed)
> code (adopted in 1988), would reduce the chance of a structural failure
> by a factor of over 10.  Not a tenth of previous codes.  This is a factor
> of ten applied to structures designed and built to what eventually became
> the 1988 UBC.
>
> What we now have, as I see it, is a class of structures which may well be
> grossly overdesigned for seismic hazards relative to all other hazards.
> This is no longer a minimum life safety code, it is a performance based
> code with an implied level of performance far above life safety, and
> totally out of kilter with other natural hazards. That is not logical or
> consistent.   It will not prevent gross soil movements, water damage,
> falling furniture, broken underground pipes, or restrain all your
> groceries from disgorging themselves from cupboards and refrigerator.  It
> won't keep your electricity, water, or other utilities from making your
> home unlivable.  All these non-structural damages went into that $15B
> figure, and none will be effected by the strength of shearwalls or
> collector elements.
>
>  If Code officials had actually known this, the 1997 UBC may never have
> been adopted.
>
> Sorry for the rant.  I'll go quietly, now.
>
> Russ Nester
> rnester(--nospam--at)juno.com
>
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