Historically the design of such foundations consisted of specifying a
foundation from 2 to 5 times the mass of the supported equipment with
small depth and large width and length preferred. Modern designs tend
to be much more economical and perform more reliably.
Without knowing more details I can not give you much detailed advice,
however, at the very least, you will have to perform a lumped mass
dynamic analysis to find the six (6) natural frequencies corresponding
to the six degrees of freedom (three directional and three rotational)
for the combined foundation. supported equipment, and perhaps, some
attached soil. Next, you will compare the natural frequencies from your
analysis with the primary and secondary frequencies of the rotating
equipment. If the two are within a factor of (+-) square root of 2
(1.41) of one another change the foundation dimensions and repeat the
above analysis. You may have to repeat this several times so if you are
not using a "canned program" at least use a computerized spreadsheat
You will also have to limit vibration amplitudes to within published
standards (see codes or occupational health and safety for your state).
If this is a particularly large installation you may also have to limit
foundation deformations such as radius of curvature for multi-bearing
rotating shafts or misalignment at couplings. The equipment supplier
will specify the standards required. If this is the case you will have
to do a full blown finite element dynamic analysis.
IMPORTANT!!! Be sure to limit your liability to the work you do. For
instance, gas compressors generate gas pressure surges which may cause
serious vibration in piping etc. which are not related to your
foundation design. Also, accessories within the equipment package may
not be properly designed or supported.
May I respectfully recommend that you have someone who is experienced
in this area help you with your first project. Should you wish to
consider me I am available and I have both the experience and the
expertise. However, I am from Canada, which would complicate
communications and co-ordination; and I am not registered anywhere in
the United States, which may make me ineligible unless you act as
engineer of record. Never-the-less, you should get someone because
these jobs are quite tricky.
H. D. Richardson
victor lee wrote:
> Hello Everybody!
> I will be designing foundation for a large machinery involving
> vibration/impact inside a proposed pre-engineered metal building. I
> understand, a similar machine at another location caused considerable
> cracking in adjacent existing concrete/masonry structures. Need help - any
> good references, rules of thumb, tips, etc. on foundation design for this
> application. Appreciate your help in advance.
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