Example

Example: Checking Foundation Tuning

A large reciprocating compressor operates at a speed of 450 RPM. It is mounted on a massive concrete block foundation. Based on soil testing and the geometry of the block, the vertical dynamic spring constant of the soil (kzk_z) is estimated to be 8.5×105 kN/m8.5 \times 10^5 \text{ kN/m}. The combined weight of the machine and the concrete block is 1200 kN1200 \text{ kN}. Determine if the foundation is safely tuned (avoiding resonance) in the vertical mode. (g=9.81 m/s2g = 9.81 \text{ m/s}^2)

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Example

Example: Natural Frequency Calculation

A 3.0 m×3.0 m3.0 \text{ m} \times 3.0 \text{ m} concrete block foundation supports a large compressor. The total mass of the machine and the concrete foundation (mm) is 25,000 kg25,000 \text{ kg}. The foundation rests on a sandy soil. Based on cyclic plate load tests, the coefficient of elastic uniform compression of the soil (CzC_z) is determined to be 4.0×107 N/m34.0 \times 10^7 \text{ N/m}^3. Calculate the equivalent vertical soil spring constant (kzk_z) and the natural frequency (fnf_n) of the foundation-soil system in the vertical mode.

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Example

Example: Amplitude of Vertical Vibration (Simplified)

Using the data from the previous example (m=25,000 kgm = 25,000 \text{ kg}, kz=3.6×108 N/mk_z = 3.6 \times 10^8 \text{ N/m}, fn=19.1 Hzf_n = 19.1 \text{ Hz}), the compressor operates at an operating frequency (fof_o) of 10 Hz10 \text{ Hz} (or ωo=20πapprox62.8 rad/s\omega_o = 20\pi \\approx 62.8 \text{ rad/s}). The machine generates a harmonic unbalanced vertical force with an amplitude P0=15,000 NP_0 = 15,000 \text{ N}. Assuming the damping ratio is negligible (Dzapprox0D_z \\approx 0) for this rough calculation, determine the theoretical amplitude of vertical vibration (AzA_z).

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Example

Case Study: Resonance Failure of a Stamping Press Foundation

A heavy industrial stamping press was installed on a massive concrete block foundation resting on a stiff clay deposit.

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Example

Case Study: Vibration Isolation in a High-Tech Facility

A new semiconductor manufacturing plant required the installation of extremely sensitive photolithography equipment. This equipment can be disrupted by vibrations as small as a few micrometers.

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