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RE: steel - vibration analysis

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David,

 

I don’t have any experience with the AISC software or FloorVibe, and what vibration calcs I ran were only with RAM SBeam or by hand, and it’s been a while for either.  But my recollection with RAM SBeam is that the program assumed no damping of any sort and that I had to put some quantity in to get a reasonable size member at the “barely perceptible” vibration level (which is what that particular project called for).  I forget exactly what that quantity was now—I think it might have been 30% of live load.  Anyway, if you haven’t already, root around in RAM to find if you need to tweak the assumed or calculated damping somewhere.

 

Gary

 

Gary J. Ehrlich, PE

Program Manager, Structural Codes & Standards

National Association of Home Builders (NAHB)

1201 15th Street, NW, Washington, DC 20005

ph: 202-266-8545  or 800-368-5242 x8545

fax: 202-266-8369

gehrlich(--nospam--at)nahb.com


From: David Topete [mailto:dtopete(--nospam--at)gfdseng.com]
Sent: Thursday, May 31, 2007 7:44 PM
To: seaint(--nospam--at)seaint.org
Subject: steel - vibration analysis

 

Checking vibration on steel framing for a mezzanine, I got 2 similar answers by following example 4.4 of AISC Design Guide 11 (Designing for Floor Vibrations) and the Floor Framing software from the www.AISC.org/steeltools downloadable software.  While those answers were similar, the analysis provided by FloorVibe via Ram Structural System indicated members being increased about 60% (conservatively).  Has anyone else encountered such a discrepancy?

 

David A. Topete, SE

Structural Engineer

 

GFDS Engineers

543 Howard St., First Floor

San Francisco, CA 94105

v : (415) 512-1301 x21

f : (415) 512-1302

dtopete(--nospam--at)gfdseng.com

www.gfdseng.com