| Summary: | Efficiency of several vibration protection patterns applicable to items of machinery inducing
harmonic and impulsive loads is assessed on the basis of the foundation displacements, accelerations
and the transfer ratio. Identification of accelerations is important due to potential negative influence
of vibration on adjacent structures. Vibration protection patterns analyzed in the article represent
a SDOF system, a scheme that has an additional inertial block and a system with a Passive
Tuned Mass Damper (PTMD). The author considers vertical oscillations of systems that have one
and two degrees of freedom by taking account of transient modes of operation of items of machinery
inducing harmonic loads (modes of activation and stopping). The two methods are employed,
including the method of normalized eigenforms and the method of transfer and impulse response
functions. The method of normalized eigenforms relies on transforming the mass displacement vector
into a linear combination of eigenforms. Solutions are obtained by applying the Duhamel integral.
The method of transfer and impulse response functions is based on a correlation between these
functions. This method proves to be efficient in respect of less than 3 DOF systems, and it doesn't
require any identification of eigenforms.
The PTMD system has proved to be particularly efficient if applied to the items of machinery
inducing harmonic loads (the fan), as the damper is tuned to the operational frequency of the
machines. The system that has an additional inertial block is mostly efficient if applied to items of
machinery inducing impulsive loads (the sledge hammer) due to smaller dynamic loads transmitted
to the foundation.
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