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Vibrations
 

Definition

A vibration gives a body (or several bodies) an oscillatory movement around a reference position (often a balanced position).

Challenges

The mechanical vibrations emitted into the environment by classified installations for environmental protection can cause a problem for the protection of local residents (building safety and impact on the occupants of these buildings).
The legislation on classified installations defines by “building”:

  • residential or work-related buildings or buildings used for any other human activity (offices, hospital, crèche, school, prison, factory etc.);
  • public buildings (place of worship, cinema, theatre, department store etc.);
  • old constructions and structures with an archaeological or historical architectural value.

Method to evaluate vibration effects

The effects of mechanical vibrations on buildings include:

  • direct effects (cracking etc.) resulting from the resonance of sustained vibrations, or excitation, repeated or otherwise but at a high level, of impulsive sources;
  • indirect effects by soil densification. The effects of mechanical vibrations on buildings are evaluated by:
    • measurements to determine the parameters of the movements observed (frequency, displacement, particulate velocity, acceleration, duration, frequency, time function and spectrum);
    • accurate levelling measurements. Studying the effects of vibrations on buildings requires the preliminary definition of the different source categories, taking into account the type of signal received, and the classification of buildings with a view to adapting the permissible tolerance to each category.
      The effects of mechanical vibrations emitted into the environment by these installations are currently evaluated using resources and methods which vary significantly depending on the operator.

The Circular of 23 July 1986 relative to the mechanical vibrations emitted into the environment by classified installations for environmental protection, aims at harmonising these resources and methods and establishing standards to prevent inconveniences to individuals or building damage. It determines vibratory limit thresholds as well as a measurement method.

Legislation

Circular of 23 July 1986 relative to the mechanical vibrations emitted into the environment by classified installations for environmental protection. This Circular is enforced by numerous ministerial orders.