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RE: Design ground accelerations

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Lynn

Many of the responses have to do with conjecture.  It is possible that the
careful code analysis will lead to the conclusion that the plan checker is
taking some provision too literally.   The code is a formal document and in
general the plan checker is not in a position to require things that are
not specifically called for in the code.

I believe that the answer may have to do with the specific code provision
the plan checker is pointing to.  Would appreciate it if you would tell us
the specific section numbers of the CBC(California Building Code)being
envoked.   Is section 1631A.2-6 being envoked for some reason?  I ask these
questions because 1631A.2-6 is the only place in the CBC that requires a
formal two level analysis.  If this is not the case then  you should be
able to tell the checker that the desired perfomance is implicitly assumed
to exist if you have complied with the CBC.

If section 1631A.2-6 applies then the world gets fuzy.  DSA has not always
specifically requested a collapse analysis when this section applies.  If I
were to do such an analysis I would base it on FEMA 273 or 356.


Mark Gilligan



_______________________________________________
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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