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Re: higher loads or better details.

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Bill Sherman wrote:
> 
> Moni Serhal wrote:
> 
> >If you compare the Rw factor for RC frame structures with shear walls,
> it dropped from 8 in the UBC 91 to 5.5 in the UBC 97, a 45% increase in
> base shear load ! This illustrates how much uncertainties there still
> are in computing the lateral loads.<
> 
> Actually the base shear load per the above changed very little - UBC 97
> provides factored loads whereas UBC provides allowable stress loads.  UBC 97
> loads may be reduced by a factor of 1.4 for comparison with UBC 91.  Thus
> (8/5.5)/1.4=1.04 for only a 4 percent increase.  Where I have found
> significant base shear differences, it has been due to changes in soil
> parameters to determine soil type.
> 

Humm thanks for this valuable info. I suspected that somewhere in the
UBC 97 there would be a new factor to reduce this difference but I
hadn't gone through it yet since I'm still using UBC 91. Anyways this
will remind me to read the whole thing before "speaking" next time :)

Moni Serhal