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RE: UBC97 question

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I would recommend checking the base shears for the two analyses.  If
everything else in both of 
the analyses is being done correctly, my guess is that the difference could
be in the scaling factor used in the dynamic analysis.  Just a thought.

Jim Hagensen,  SE

> -----Original Message-----
> From:	Ken Wong [SMTP:tsunami(--nospam--at)]
> Sent:	Tuesday, March 02, 1999 9:11 AM
> To:	seaint(--nospam--at)
> Subject:	UBC97 question
> I am forwarding this query for discussion.
> 	To Whom It May Concern:  
> "My name is Michael Kingsmore and I work in the Structural Engineering
> Department at Sherlock, Smith and Adams, Inc. (an A/E firm) in Montgomery,
> Alabama.  Most of our work is done for the Department of Defense -
> specifically medical facilities for the  DOD.  
> "Generally, when our firm encounters projects where seismic analysis is
> necessary, we consult with firms specializing in seismic design.
> However, we are interested in doing seismic analysis in house and are in
> the
> process of performing our own dynamic analysis on a current project.  
> "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).  It would seem to me that the
> static approximation would be much more conservative than the dynamic
> approximation.  
> "I would appreciate any information or thoughts that would shed some light
> on this dilemma.  Thank you for your time.  
> Michael A. Kingsmore  
> e-mail:  kingsmore_m(--nospam--at)  
> Structural Department  
> Sherlock, Smith and Adams, Inc.  
> 3047 Carter Hill Road  
> Montgomery, AL   36111-0006  
> (334) 263-6481  
> FAX: (334) 264-4509  
> ===============================================================
> Ken Wong			Tel: 510-231-9564
> PEER Bldg. 451 RFS		Fax: 510-231-9461
> 1301 South 46th Street     E-mail: info(--nospam--at)
> Richmond, CA  94804-4698
> ===============================================================