General Requirements of Machine Foundations during Design and Detailing

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The following general requirements of machine foundations shall be satisfied and results checked prior to detailing the foundations. 1. The foundation should be able to carry the superimposed loads without causing shear or crushing failure. 2. The settlements should be within the permissible limits. 3. The combined centre of gravity of machine and foundation should, as far as possible, be in the same vertical line as the centre of gravity of the base plane. 4. No resonance should occur, hence the natural frequency of the foundation–soil system should be either too large or too small compared to the operating frequency of the machine. For low-speed machines, the natural frequency should be high. 5. The amplitudes under service conditions should be within permissible limits which are prescribed by the machine manufacturers. 6. All rotating and reciprocating parts of a machine should be so well balanced as to minimize the unbalanced forces or moments. 7. Where possible, the foundation should be planned in such a manner as to permit a subsequent alteration of natural frequency by changing base area or mass of the foundation as may subsequently be required.

Fig: Machine Foundation

From the practical point of view, the following requirements should be fulfilled. 1. The groundwater table should be as low as possible and groundwater level deeper by at least one-fourth of the width of foundation below the base plane. This limits the vibration propagation, groundwater being a good conductor of vibration waves. 2. Machine foundations should be separated from adjacent building components by means of expansion joints. 3. Any steam or hot air pipes, embedded in the foundation must be properly isolated. 4. The foundation must be protected from machine oil by means of acid-resisting coating or suitable chemical treatment. 5. Machine foundations should be taken to a level lower than the level of the foundations of adjoining buildings. Read More: Types of Machine Foundations Vibration Analysis of Machine Foundations