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Fwd: Re: Floor Vibration

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>On Sun, 16 Mar 1997, R K Hagens, P.E. wrote:
>> Does anyone know of a technical guide or resource for designing or
>> retrofitting buildings with floor vibration control problems?  I have a
>> client that wants to install a VERY sensitive device that requires
>> vibration amplitudes be limited to 1 micron or less at a frequencies of 5
>> Hz or greater.
>We get requirements like that fairly regularly here at Lawrence Berkeley 
>National Lab. The solution seems to be in isolating the EQUIPMENT. Even 
>when we build a brand new building to house such equipment (typically 
>electron microscopes) we design isolation for the equipment. I don't 
>recall EVER retrofitting the building itself. Vibration isolation systems 
>are usually just the opposite of good seismic design, so it can be a 
>.    .    .   .   .  .  .  .  . . . . . ...........................
>Bob Shilling, SE             Berkeley, CA          shilling(--nospam--at)

        We, too are designing vibration isolation systems for the
semiconductor industry. SEMs are just one type of equipment that you have to
deal with.  Fortunately most of the buildings in Silicon Valley have been
designed with "vibration in mind".  But Bob Shilling is right that it is
much easier and cheaper to isolate the tool (passive or active isolation
systems) than do the structural modifications to the buildings.  
        It is quite time consuming task to design the active isolation
system.  If the floor vibration is whithin the spec, than there you are OK
(assuming that your tool sits directly on the floor).  You would also need a
little more specific vibration spec (is it p-p, 0-p or RMS).  But whichever
way you go, first thing that you need to do is to hire a vibration
consultant to measure the vibrations at the site.  Let me know if you need
any names.

Sasha Itsekson
Huntigton Design Associates
Oakland, CA

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Richard Lewis, P.E.
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