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Re: UBC97 question

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Regarding the following question raised: 
 
>The governing code for the project is UBC 97.  Our current frame design 
software is capable of Static Force Procedure and Dynamic Analysis 
(utilizing UBC Normalized Response Spectra, NEHRP Normalized Response 
Spectra or El-Centro Response Spectra).  I am having trouble understanding 
why there is such a huge difference in member forces and 
displacements/drifts between the results obtained using the Static Force 
Procedure and results obtained using the Dynamic Analysis.  The Dynamic 
Analysis results are much higher than those obtained through the Static 
Force Procedure (typically 3 times larger).  < 
 
The above procedure refers to "Normalized Response Spectra" used in the 
software - this terminology is consistent with the 1994 UBC but the 1997 UBC 
refers to "Design Response Spectra".  At zero period, the 1994 "normalized" 
spectra had a value of 1.00 whereas the 1997 UBC has a value of "Ca".  In 
effect, the 1994 curve is "normalized" to Ca = 1.00.  Thus it is possible
that 
the software is using a value of Ca=1.00 for the normalized dynamic analyses 
vs a much lower Ca for the static procedure - which could easily cause the 
magnitude of difference in results noted.  I suggest that the software 
methodology with respect to response spectra values be reviewed.