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RE: steel - vibration analysis

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David -
I've used the FloorVibe software, but only the share ware version that AISC had on their website for awhile.  Not sure if they have a better / commercial version or not. Anyway, the problem that I see with this software is that everything has to be nice and orthogonal.  I didn't see a way to enter in the types of skewed project grids that I really see on design projects.  My impression was that it was even more limited than that, but it's been awhile so I can't quite remember what seemed so limiting about it. 
I don't have any experience with RAM, but keep in mind that the values handed to FloorVibe from RAM would have to be simplified and approximated to fit into the very rigid constraints of what FloorVibe is allowed to do.  The assumptions and simplifications that RAM makes may not be all that good.  If the guys at RAM really new how to to floor vibrations, then I'd think that they would just do the calculation themselves?  This may not be simple for the average engineer who does this calculations once every few years.  However, it's shouldn't be all that difficult for a development team whose job it is to get it right once when they're programming it. 
Disclaimer: I work for a structural engeineering software company (RISA Technologies) that competes against RAM in the Floor design market and which also brags about our ability to do DG-11 floor vibration calculations.  I'm ridiculously busy these days, but if you were to e-mail me a good description of your floor system or some drawings and such, then I can try to get one of our engineers to enter this into our Floor program to demonstrate our ability to do the DG-11 calculations accurately.
Josh Plummer, SE
RISA Technologies

From: David Topete [mailto:dtopete(--nospam--at)]
Sent: Thursday, May 31, 2007 4:44 PM
To: seaint(--nospam--at)
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 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


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