The design of foundations for machine requires careful study of vibration characteristics of the foundation system. The design of foundations of turbines, motors, generators, compressors, forge hammers and other machines, having a rhythmic application of unbalanced forces require special knowledge of theory of harmonic vibrations. Inertial forces of rotating elements of machines contribute, besides their static loads additional dynamic loads. The machinary vibration influences adversely the foundation supporting soil by densifying it which may, in turn, cause differential settlement of the soil and foundation.
Usually mass concrete is used for machine foundations. The excessive vibrations can be eliminated by use of heavy foundations. As a rough guide, the ratio of the weight of foundation to the engine weight may be kept beteween 2.5 to 3.5 in most of the machines.
Manufactures recommend the weight of foundation suitable for their machines, based largely on experience. The permissible bearing pressure under dynamic loads may be taken as 1/2 to 1/4 of the premissible bearing pressure under static loads.
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