Vibrations in supporting structures
According to DIN EN 1995-1-1, paragraph 7.3, it must generally be “ensured for load-bearing structures that frequently expected actions do not cause vibrations that impair the function of the structure or cause unacceptable discomfort to the users”. Vibration verifications are therefore required for residential or office ceilings. The most important physical quantities that influence the vibration behaviour of ceilings are the first natural frequency, the stiffness and the damping behaviour of the ceiling construction.
The significance of the natural frequency
To prevent the ceiling from vibrating, a sufficient distance between the excitation frequency and the first natural frequency should be aimed for. When walking, for example, an excitation of approx. 4.00 Hz occurs. Eurocode 5 therefore requires a first natural frequency of at least 8.00 Hz for a sufficient distance to the excitation frequency.
to avoid vibrations
Slabs that are susceptible to vibrations can be improved by additional supports or reinforcement measures (e.g. higher stiffness). A load distribution transverse to the span direction as well as higher damping also contribute to improving the vibration behaviour. If it is not possible to achieve the required minimum frequency, the vibration can be verified by limiting the vibration acceleration.
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