Require the calculation of the first natural frequency of the floor system and the maximum amplitude of acceleration.
Floor system frequency of vibration calculation.
Design for sensitive equipment.
The natural frequency of the system assuming a single degree of freedom can be calculated by.
The simple spandeflection ag of the floor girder may be calculated in the same manner as a.
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.
If more flexibility is needed air springs are used.
The system has a fundamental frequency which corresponds to the first lowest mode of vibration.
Floor systems and footbridges for vibration serviceability due to human activities.
Supporting the floor system also af fects the natural frequency of the floor 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.
Hz 1 3 13 2 1 2 1 2 1 g w kg.
Observe the behavior when the excitation frequency coincides with the natural frequency of the system.
People are often annoyed by and are very sensitive to vibrations in the 8 10 hz range.
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.
Damping by furniture and finishing e g.
Try this test for each type of excitation.
For best results the frequency should be 15 hz or higher.
False floor l spread of energy throughout the whole structure.
Watch what the system is doing.
Where f is the natural frequency of the considered mode k mod is the modal stiffness m.
P o is 65 lb for office.
If the forcing frequency is close to the natural frequency of the system and the system is lightly damped huge vibration amplitudes may occur.
Both human comfort and the need to.
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.
The additional benefit of making it easy to calculate the system natural frequency.
In this mode the vibration reaches maximum amplitude in one position an antinode at mid span of the beam.
Coil spring isolators are available in up to 3 static deflection.
In reality only f n and w require calculations.
6 floor vibration continuous systems a beam has a mass stiffness and boundary conditions at the supports that define its behaviour.
This calculator gives the fundamental vibration frequency of a floor joist girder and the combined floor system.
