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RE: 1.1Load Factor in 1997 UBC

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In response to the comments of Ben Yousefi:

Why does the 97 UBC base shear value need to be greater than or equal to

the 94 UBC base shear value?  If the research behind the recent code
changes indicates that the new acceleration values are appropriate, why
do they need to be "compensated" for?  This would seem to suggest that
you believe the new code accelerations are faulty.  Even assuming that
you believe the base shear values should only increase from one code to
the next, the shape of the
acceleration/period curve is different between the two codes, so a
linear attempt to adjust the 97 Code values in one region would
necessarily be overly conservative for other regions (0.5s - 1.0s, >
2.75s).  Further, as can be seen from the tables in the Ghosh article,
the values are almost identical for special moment resisting frame.  The

disparity between the two codes at short periods applies primarily to
bearing wall systems.  So many things have changed between the two codes

(C gone, Cv and Ca introduced, Rw changed to R, redundancy introduced)
and so much new research has been introduced, it seems rather arbitrary
to keep the 1.1 in the name of insuring the one particular base shear
case does not decrease going from the 94 UBC to the 97 UBC.

Paul Crocker