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Re: Resonance

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Rainier,

        In theory you may not have a resonance problem.

        In practice, however, it is very unlikely in my opinion that you will
have your centre of mass, your centre of spring resistance, and your centre of
action of your forcing function all perfectly aligned.  You should, therefore,
expect at least some sympathetic vibration from a Mode 1 forcing function
acting at Mode 2 natural frequency.  This can be analysed but the results are
sensitive to both the accuracy and detail of the analysis and the accuracy to
which you know the damping ratios.

        I would personally prefer to avoid the problem by adjusting the
natural frequency if that is practical.

        Hope this is helpful.

Regards,

H. Daryl Richardson

RainCat1(--nospam--at)aol.com wrote:

> Say I have a structure supporting a machinery. I did a modal analysis and
> determine that the natural frequencies (in cps) of the structure are as
> follows: mode 1 = 3, mode 2 = 5, mode 3 = 10. The rated frequency of the
> machinery = 5. The machinery has up & down vibration which is more similar
> with mode 1 than mode 2.
> Should I expect resonance problem? I'll appreciate any input.
> Thanks & regards!
>
> Rainier Catubig
> San Diego, California
>
>
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