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RE: 14 story concrete shear wall building

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Scott:

Here in California, most building officials would likely classify that
building as potentially vulnerable and still occupiable in its unretrofitted
state rather than dangerous. In order to be dangerous there would generally
be a need to demonstrate an "imminent threat" to the public either inside
the building or around the perimeter. Earthquake risk is not generally
considered imminent - except perhaps in the case of aftershocks and damaged
buildings.

As a related example, California has 25,000 unreinforced masonry buildings
in high-seismic regions nearly all of which would not meet the dangerous
building base shear criteria. However, state law classified them back in
1986 as "potentially hazardous" which is now a bit archaic language. This
differentiated them from "dangerous" buildings but nevertheless warranted
some consideration of mitigation action. So far, about half of these 25,000
URM buildings in over 200 jurisictions have been retrofitted to varying
degrees, most in compliance with versions of ICBO's Uniform Code for
Building Conservation, Appendix Chapter 1 or local variants thereof. If the
same dangerous building base shear criteria were applied to many of these
retrofitted URM buildings, they would not comply. No jurisdiction in
California has recently required the retrofit of nonductile concrete frame
buildings, let alone those with shear walls which are generally much less
vulnerable to collapse or other forms of life-threatening response to ground
shaking. A few CA jurisdictions have voluntary retrofit provisions for NDC
Frames on the books, but there are just a small number of owners who are
voluntarily retrofitting.

I'm just reading daily digests of SEAINT so further correspondence from me
if needed may take place tomorrow. If you need some specific info about
local ordinances throughout California today, please email me directly.

Fred Turner, Staff Structural Engineer, California Seismic Safety
Commission, a public policy advisory agency, fturner(--nospam--at)quiknet.com, 1755
Creekside Oaks Dr. #100 Sacramento, CA 95833 916-263-0582 Phone 916-263-0594
Fax


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