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RE: Design ground accelerations

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There are 3 primary questions which need to be resolved:

1. Does the California Building Standards Administrative Code supersede the
local code, i.e. the 1997 UBC, for this application. 

2. What constitutes an acceptable "Geologic Hazards Evaluation"?

3. What seismic probability requirements are there? 

I can't answer these questions for you, but I have performed designs of
public utility structures which are based on such geotechnical parameters in
excess of minimum code requirements. This is usually sorted out with the
Owner before seismic analysis is performed. Were you "told" to design per
the 1997 UBC or did you "assume" that it was the "governing code"? 

William C. Sherman, PE
CDM, Denver, CO
Phone: 303-298-1311
Fax: 303-293-8236
email: shermanwc(--nospam--at)

> -----Original Message-----
> From: Lynn [mailto:lhoward(--nospam--at)]
> Sent: Wednesday, September 11, 2002 2:23 PM
> To: seaint(--nospam--at)
> Subject: Design ground accelerations
> We have received plan check corrections on a Fire
> Station we designed.  The governing Code is the 1997
> UBC.
> The plan checker has sited a section in the
> Geotechnical report called "seismic shaking", that says
> the building should be designed for .6g without
> suffering significant damage, and .8g without
> structural collapse. 
> The plan checker then goes on to site the California
> Building Standards Administrative Code as requiring
> that the building be designed for the ground
> accelerations given in a Geologic Hazards Evaluation.
> The plan checker is asking for additional structural
> calculations showing that the building is able to
> withstand peak ground accelerations of .6g's without
> significant damage, and .8g's without structural
> collapse.
> What we have done is just used the 1997 UBC, taken into
> account the near source factors, and factored again for
> an essential facility.  Beyond that, I am not sure we
> are required to do anything.
> The language used by the plan checker seems to relate
> more to NERHP provisions and the IBC design
> methodology.
> Has anyone else come up against this, and if so, what
> have you done to satisfy the plan checker.
> Thanks
> Lynn

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