Free Engineering Tool #222

Foundation Natural Frequency Calculator

Calculate the natural frequency of a machine-foundation system from soil stiffness, contact area and total mass.

fn = √(k·A/m)/(2π)Soil-FoundationAuto-Calc

Results

Natural Frequency

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Angular Frequency ω

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Equivalent Stiffness

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Where k_s is soil dynamic stiffness (MN/m³), A is foundation contact area, m is total mass.

The operating speed should be at least 30% away from fn to avoid resonance.

Operating speed should be >1.3× or <0.7× the natural frequency to avoid resonance.

From geotechnical investigation. Typical: clay 10-40 MN/m³, sand 40-100, rock 100-500.

Yes. Rectangular foundations have different stiffness in each direction. Use the smallest dimension for conservative estimate.

Soil provides significant damping (5-15%). This limits peak amplitudes at resonance but does not change fn significantly.

Yes, by changing mass (height) or base area. Adding mass lowers fn, increasing area raises it.