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 J. Ehrlich, PE
Program Manager, Structural Codes & Standards
National Association of Home Builders (NAHB)
ph: 202-266-8545 or 800-368-5242 x8545
fax: 202-266-8369
From: David Topete [mailto:dtopete@gfdseng.com]
Sent: Thursday, May 31, 2007 7:44 PM
To:
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
v : (415) 512-1301 x21
f : (415) 512-1302
dtopete@gfdseng.com