If vibrations have a permanent effect on people, even small amplitude vibrations can be perceived as unpleasant or annoying. The influencing factors can be divided into three categories:
- Type of impact (e.g., impact-like, harmonic, duration, direction, frequency).
- Subjective perception (e.g. posture, form of movement, activity, age, ...)
- Environmental condition (e.g. time of day, type of construction, temperature, ...).
For practical purposes, it therefore makes sense to apply different assessment criteria for individual types of structures (floor slabs, grandstands, bridges, ...) according to their use.
Not only from a legal point of view, however, a distinction must also be made between vibrations due to external and internal sources of excitation.
Vibrations due to external sources
For this case ("Immission protection"), there are standards that specify criteria for their assessment. These are, for example, the standards DIN 4150-2, ISO 2631, VDI 2057, BS 6472, Ö-Norm ISO 2631, Ö-Norm S 9012, etc. Low-frequency wind vibrations from buildings occupy a special position. A typical example of external sources are vibrations from traffic.
Schwingungen durch interne Quellen
Vibrations generated by the persons themselves or by persons in the same building or on the same structure (e.g., by machines).
For the case ("self-generated" vibrations), VDI 2038 is to be applied in Germany.
Limit or reference values
In principle, comfort criteria can be defined by vibration displacements, vibration velocities, or accelerations, or by quantities derived from these. In Germany, the following values are generally used to assess comfort:
- the KB value (DIN 4150-2; e.g., floor slabs)
- the max. acceleration occurring over time (e.g., bridge vibrations).