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Re: UBC97 question

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What software are you using anyway? Check your Static Base Shear against your REDUCED elastic response base shear. See UBC 97 1631.5.4

Jerome AM Tan
Makati City, Philippines

______________________________ Reply Separator _________________________________
Subject: UBC97 question
Author:  MIME:tsunami(--nospam--at) at INTERNET
Date:    03/02/99 5:21 PM

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

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