Floor System Frequency Of Vibration Calculation

Design for sensitive equipment.

Floor system frequency of vibration calculation.

Both human comfort and the need to. Unlike the sdof system which has a single natural frequency and corresponding mode of vibration a continuous system theoretically has an infinite number of natural frequencies and associated modes. 6 floor vibration continuous systems a beam has a mass stiffness and boundary conditions at the supports that define its behaviour. Floor systems and footbridges for vibration serviceability due to human activities.

At first glance the criteria might look a bit formidable it certainly is different than the older criteria. The system has a fundamental frequency which corresponds to the first lowest mode of vibration. For best results the frequency should be 15 hz or higher. Watch what the system is doing.

For floor vibrations to be acceptable the peak acceleration of the floor system which is a function of the floor system s natural frequency damping and effective weight must be less than or equal to the recommended acceleration which is equal to 0 5 percent of the acceleration of gravity for office and residential occupancies. False floor l spread of energy throughout the whole structure. If more flexibility is needed air springs are used. Observe the behavior when the excitation frequency coincides with the natural frequency of the system.

Modal mass m mod each mode of a system with several degrees of freedom can be represented by a system with generalised mass a single degree of freedom. P o is 65 lb for office. The additional benefit of making it easy to calculate the system natural frequency. The natural frequency of the system assuming a single degree of freedom can be calculated by.

Hz 1 3 13 2 1 2 1 2 1 g w kg. Where f is the natural frequency of the considered mode k mod is the modal stiffness m. Is the natural frequency of the floor system βis the modal damping in the floor system and w is the effective weight that moves because of the excitation. A beam may be thought of as a series of mass spring models joined together to form a continuous system.

Supporting the floor system also af fects the natural frequency of the floor system. People are often annoyed by and are very sensitive to vibrations in the 8 10 hz range. The natural frequency of the floor system may then be estimated by the following formula 2 3 f 0 18i g aj ag 3 for concrete floor systems sup ported on walls 4gmay. Coil spring isolators are available in up to 3 static deflection.

Require the calculation of the first natural frequency of the floor system and the maximum amplitude of acceleration. Try this test for each type of excitation. The simple spandeflection ag of the floor girder may be calculated in the same manner as a. In this mode the vibration reaches maximum amplitude in one position an antinode at mid span of the beam.

In reality only f n and w require calculations.