NEWS

RIVAS – Vibrations: Ways out of the Annoyance

A summary of outcomes

Please find the final brochure of the RIVAS project under Results and Publications.


The RIVAS FINAL CONFERENCE

“Vibration – Ways out of the annoyance”, was held in Brussels, on 21 November 2013

Please find here more information.

 

Major outcomes

The RIVAS project is strongly end-user driven in order to ensure an utmost exploitation of results in practice and to prepare an extensive and fast implementation of technical developments.

The key deliverables of the RIVAS project are:

  • Assessment of the benefits of mitigation measures in terms of human response and agreed protocol for the evaluation of annoyance and exposure to vibration
  • Agreed measurement protocols to assess and monitor the performance of antivibration measures
  • Agreed protocol to characterise vibration response properties of soils
  • Guidelines for track and vehicle maintenance geared towards low vibration
  • Mitigation measures for ballasted and slab track
  • Guidelines for the design of transmission mitigation measures under/next to the track
  • Guidelines for the design of low vibration vehicles


Generation of vibration by rail traffic

A number of mechanisms vibration can be significant. Dynamic forces are generated by trains rolling with irregular wheel profiles over irregular track profiles. This mechanism is similar to the excitation of rolling noise. However, it is characterised by much longer wavelengths of 'roughness'. On the wheel, it is represented by out-of-roundness. Additional dynamic forces are generated as the wheels traverse switches and crossings or badly maintained rail joints. Uneven track support may give rise to additional dynamic displacements under the loads of the vehicles.

Another generation mechanism arises from the time-dependent displacement of the ground beneath the moving axle loads. This is sometimes called the 'quasi-static' excitation mechanism. For conventional train speeds this vibration remains in the near field (about 1/4 of a wavelength from the track). However, for very soft ground the wavelengths are long, so buildings can be affected.

Various types of rail traffic give rise to vibration in different frequency ranges from different mechanisms.

The most important vibration frequencies range from about 5Hz to 100Hz. Generally, freight traffic is the most important source of vibration and vibration-induced noise. A special problem arises on very soft ground. Freight traffic causes vibration at very low frequencies (below 10 Hz) which can still be strongly perceptible at distances on the order of 100 m from the track.

Urban, interregional and high-speed passenger trains may also cause significant levels of low-frequency, perceptible vibration. However, urban traffic, metropolitan and light rail vehicles more often give rise to vibration that has a greater impact at higher frequencies than vibration from freight trains.

Vibrations from circa 30 Hz to 250 Hz which are transmitted through the ground may excite bending in the floors and walls of a building which then radiate noise themselves directly into the rooms.