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Re: Foundation Vibration Design

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In several situations of equipments, particularly those that run 
at high frequencies such as turbines, impellers etc, it is not
possible to make foundation block frequency greater than the 
equipment operating frequency.  In the process of starting, the
equipment passes through the natural frequency of foundation 
leading to transient tuning.  Most equipment design specifications
also limit the amplitude of motion during this transient tuning.

On Fri, 30 Jan 1998, Kathleen  A. O'Brien wrote:
> >> NAVFAC DM7 recommends that the "natural frequency of the 
> foundation block soil system should be less than one-half or greater 
> than two times the equipment operating frequency."  In most cases 
> this is possible<<
> Wouldn't it be better to keep the foundation block soil system frequency
> GREATER than the equipment frequency at all times? I look at it this way:
> When the equipment is not running, it's frequency is zero. Turn it on, and
> the frequency will vary from 0 to its maximum natural frequency. If the
> Foundatiuon system frequnecy is less than the Equipment frequency, at some
> point the two will be equal. Then I would think we would have some
> amplification (a la the Tacoma Narrows bridge).

Ravi Sinha, Ph.D.		email: rsinha(--nospam--at)
Assistant Professor		       rsinha(--nospam--at)
Department of Civil Engineering	       Phone: (91-22)-578-2545 Ext. 7336
IIT, Powai, Bombay - 400 076, India    Fax: (91-22)-578-3480, 578-3557