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Re: '97 code seismic map

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I recently compared the 1997 UBC requirements with the 1994 UBC requirements
for a project in Seismic Zone 2B, and also found the lateral coefficient to
be
much higher in 1997.  I did account for the 1.4 ultimate stress vs allowable
stress factor (which generally shows up as reduced R-factors) - but the soil
classifications are what had the big impact on net load increase.  In the
1994
code I could use C=2.75  without regard to soil type.  In the 1997 code,
soil
type must be considered in determining Ca and the value can vary
significantly
with "soil" type.  Actually, it looks like anything less than rock will
increase the net lateral coefficient for my case.  Thus it would appear that
significantly higher lateral seismic forces will apply to many projects
under
the 1997 code.