Deal all,
I am conducting a numerical analysis of machine foundation resting on soil. It would be very helpful if someone can provide me a reference stating the lowest and highest applicable frequency of vibration of machines during starting and turning off.
Many thanks
Since the answer of your question depends on the type of vibratory machine, soil type, the damping factor, geometrical layout of the foundation and soil-foundation dynamic interaction, respecting the following items help you to estimate the lowest and max. values of frequency:
- There should be no resonance; that is, the natural frequency of the machine foundation-soil system should not coincide with the operating frequency of the machine. In fact, a zone of resonance is generally defined and the natural frequency of the system must lie outside this zone. The foundation is high tuned when its fundamental frequency is greater than the operating speed or low tuned when its fundamental frequency is lower than the operating speed.
- The amplitudes of motion at operating frequencies should not exceed the limiting amplitudes, which are generally specified by machine manufacturers. If the computed amplitude is within tolerable limits, but the computed natural frequency is close to the operating frequency, it is important that this situation be avoided.
- The natural frequency of the foundation–soil system should not be whole number multiple of the operating frequency of the machine to avoid resonance with the higher harmonics.
- The vibrations must not be annoying to the persons working in the shops or damaging to the other precision machines. The nature of vibrations that are perceptible, annoying, or harmful depends upon the frequency of the vibrations and the amplitude of motion.
The geometrical layout of the foundation may also be influenced by the operational requirements of the machine. The failure condition of a machine foundation is reached when its motion exceeds a limiting value which may be based on acceleration, velocity or amplitude.
I hope this explanation is useful for you.
Best of luck in your research.
Since the answer of your question depends on the type of vibratory machine, soil type, the damping factor, geometrical layout of the foundation and soil-foundation dynamic interaction, respecting the following items help you to estimate the lowest and max. values of frequency:
- There should be no resonance; that is, the natural frequency of the machine foundation-soil system should not coincide with the operating frequency of the machine. In fact, a zone of resonance is generally defined and the natural frequency of the system must lie outside this zone. The foundation is high tuned when its fundamental frequency is greater than the operating speed or low tuned when its fundamental frequency is lower than the operating speed.
- The amplitudes of motion at operating frequencies should not exceed the limiting amplitudes, which are generally specified by machine manufacturers. If the computed amplitude is within tolerable limits, but the computed natural frequency is close to the operating frequency, it is important that this situation be avoided.
- The natural frequency of the foundation–soil system should not be whole number multiple of the operating frequency of the machine to avoid resonance with the higher harmonics.
- The vibrations must not be annoying to the persons working in the shops or damaging to the other precision machines. The nature of vibrations that are perceptible, annoying, or harmful depends upon the frequency of the vibrations and the amplitude of motion.
The geometrical layout of the foundation may also be influenced by the operational requirements of the machine. The failure condition of a machine foundation is reached when its motion exceeds a limiting value which may be based on acceleration, velocity or amplitude.
I hope this explanation is useful for you.
Best of luck in your research.
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