Dynamic Response of a Machine Foundation in Combination with Spring Mounting Base and Rubber Pad

Abstract

The effect of two different combinations of a spring mounting base and a rubber pad sandwiched between the machine base and its concrete footing block was examined experimentally. The machine was subjected to steady state horizontal harmonic excitation with the help of the Lazan mechanical oscillator. Experiments were performed by inserting a spring cushioning system between the machine base and its concrete footing. In addition, two additional series of experiments were carried out by placing a rubber pad either just above or below the spring cushioning system. It was clearly noted that an employment of a spring cushioning system, as an active isolation measure, becomes the most effective when the rubber pad is kept just below the machine base. For different combinations of the spring mounting base and rubber pad, two different modes of resonance were clearly observed and the peak amplitudes of vibrations were found to be associated always with the second mode; the predominant frequencies associated with the peak amplitude of vibrations (second mode) were found to be significantly greater than those without the employment of any isolation system in which case only a single mode of resonance was observed. It is expected that the study will be beneficial for assessing the performance of the machine foundations with the employment of springs and rubber pad.