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RE: Vibrating Equipments

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RajSTC(--nospam--at)aol.com wrote:
 
> If the equipment can produce vibration that has to be contended with in 
> design, the equipment manufacturer will provide the forces for which
supports 
> should be designed for.  Ask the manufacturer about his experience with
the 
> typical foundation for similar installations.

While an equipment supplier can provide design forces at support points for
equipment operating loads, these should not be assumed to account for
vibration effects at the support structure. If the equipment vibration is
significant and is close to the natural frequency of the support structure,
there could still be significant problems. (For minor equipment, arbitrary
load increases may be adequate.) I've seen various rules of thumb regarding
the mass of a concrete foundation on grade relative to the equipment weight
to handle vibration, but this should be considered an approximate method and
may not be adequate for significant vibration problems.  

> Incidentally, many of the so called "vibration producing equipment" do not

> produce serious dynamic loading on the foundation.  For example, many of
the 
> compressors can be installed on a nominal concrete pad.  

This is where I would use the mass ratio method. However, the real problem
is how to determine when a vibration problem is a "serious dynamic loading"
problem and when it can be considered to be a minor concern. Does anyone
have some good rules of thumb for when equipment vibration and structural
natural frequencies need not be evaluated in detail?