Frequency response analysis of multi-degree-of-freedom system with harmonically varying damping

Abstract

This paper analyzes effects of harmonically varying damping on a multi-degree-of freedom system. Our recent research applied the method of the harmonically varying damping to vibration mitigation of a single-degree-of-freedom structure with sinusoidal base excitation having two frequencies. In the study, an ideal variable damper is used in conjunction with the secondary sinusoidal base excitation to reduce response due to the primary base excitation. If the primary sinusoidal base excitation contains the natural frequency of the system, resonance is induced. However, another resonance can be generated by the modulated component caused by the variable damping device and the secondary base excitation. The additional resonance is adjusted to be out of phase with the primary response, resulting in effective control of the structure. However, no such study considering the multi-degree-of-freedom system has been conducted. This paper presents the effect of the harmonically varying damping on the multi-degree-of-freedom system, especially; the influence on two structures in parallel with a variable damper between there is discussed.