Lines 1 & 2
Study to optimise track and viaduct conditions and determine maintenance strategies.
Study of the track type to be used on two prestressed concrete bridges in order to avoid any coincidence between resonance frequencies of the track and the bridges. These studies included finite element modelling of the bridges, updating of these numerical models based on measured dynamic behaviour of the bridges and definition of the optimal track stiffnesses based on those results.
RER line A1, Pecq bridge
This study was very similar to the one described above, except for the higher speed and higher axle loads. The existing direct track fixation system was modified to reduce the emitted noise.
A complete static and dynamic analysis of this old existing steel bridge was done by measurements and computations. A special track system was designed (direct fixation on steel) in order to minimize the forces going into the bridge structure. In this way the life time of the bridge was increased with more than 50 years and the heavy axle freight trains are now able to pass at 80 km/h (instead of 10 km/h before the installation of the new track). The special track system also reduces the emitted noise in comparison with a classical direct fixation system with more than 3 dB(A).
Noise and vibration study of this mixed elevated structure, consisting of prefabricated concrete beam and steel parts, in order to limit to allowable values the noise radiated in the environment during tramway passages at a maximum speed of 50 km/h.
Tramline 2, Bridges of Sèvres and Suresnes
This project involved a dynamic analysis of the bridges and the design of a new direct track fixation system on the steel structure aimed at reducing the emitted noise. The analysis included dynamic finite element models, experimental modal analysis of the bridges, measured (existing) and predictive noise maps in their environment.
Metro line 5, Austerlitz viaduct
This study required the determination of the dynamic behaviour of this steel viaduct in order to reduce the emitted noise (ballasted track). This study implied an experimental modal analysis of the viaduct and a finite element calculation of its dynamic behaviour. Noise simulation studies were carried out in order to simulate the emitted noise as a function of the track type. A very flexible ballast mat was designed and installed and this resulted in a noise reduction of some 5 dB(A).
Metro line 2, north viaduct
This project involved a dynamic analysis of the viaducts and the design of a new direct track fixation system on the steel structure in view of reducing the emitted noise. The analysis included dynamic finite element models, experimental modal analysis, measured (existing) and predictive noise maps. The newly designed track system (ballastless) was installed and resulted in a noise reduction of more than 4 dB(A).
Noise and vibration study of this steel bridge built on concrete supports, above which will be a hanging steel structure supported by steel cables connected to a narrow tower 104 meters high, in order to limit to allowable values the noise radiated in the environment during tramway passages.
Study of the noise radiated by this steel frame bridge located in a residential area and design of solutions in order to reduce the nuisance into nearby buildings.
HST, Antoing viaduct
Dynamic computations of this long concrete viaduct were made for SNCB in order to demonstrate a dynamic design methodology. Following analyses were made dynamic behaviour of the viaduct (calculation of dynamic characteristics, computation of dynamic forces and of the vibration levels of the viaduct), vibrations in the HST cars during passage over the viaduct, noise emission of the viaduct. Noise and vibration measurements during the first trial runs with the HST at high speed showed the great precision of the computation procedure. The proposed methodology is adopted by SNCB/NMBS for computing the dynamic behaviour of similar structures.
Enghien les Bains (FR)
Analysis of the noise radiated by this bridge into the environment and design of solutions aimed at reducing this noise. This study included finite element modelling of the bridge, an updating of this model based on experimental modal analysis of the bridge, the computation of the acoustic radiation of this updated model and a comparison with acoustic spectra measured in the environment of the bridge. The updated numerical models have been used to evaluate the impact on the acoustic radiation of the bridge of some structural modifications of the bridge.