Propagation of vibration in ground and structures
MEFISSTO is calculation software for propagation of vibration in ground and structures. It is based on additional digital techniques of finished elements and #borderline finished elements. For example, it permits the dimensioning of transmitted vibration reduction systems for buildings, or the carrying out of preliminary studies on the risk of structure-borne noise in buildings in proximity to railway tracks, either on the surface or in tunnels.
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Advantages of MEFISSTO
Simplified data entry
The user defines the materials and a list of domains. The geometry is simply defined by bearer segments or simple objects (polygons, arcs of circles). Simple mesh density criteria per wave length and a minimum number of elements are applied to each frequency. The entry of geometry (tunnel, etc.) can rapidly be obtained by entering points defining a contour based on an image.
Optimising of calculation time
The BEM and FEM meshes are generated for each frequency. The FEM parts are condensed on nodes coupled to BEM areas. The FEM meshes are organised to reduce the height of matrix columns.
FEM/BEM modularity as a function of domains
The chosen domains are selected, then modelled in BEM or FEM. Infinite homogeneous domains such as ground layers can easily be taken into account thanks to BEM. On the contrary, complex domains comprising multiple heterogeneities (track laying system, building foundations) are more easily modelled as FEM domains.
2D, 2.5D Versions
2D calculation is possible but not recommended as a preliminary step and in comparison of situations.
On the other hand, 2.5D calculation is well suited, particularly to railroad problematics In fact, this type of calculation supposes an invariable geometry in a given direction, an approach suited to railway tracks or tunnels. 2.5D formalism is implemented for both BEM and FEM methods. With each frequency, it relies on a series of calculations for the different wavelengths.
Taking into account multi-layer #floors, ground, soil
Complex stratification profiles are described simply by contours ended at their extremities by elements redefined by each frequency, thus benefitting from high damping in #floors/ground/soil.
Taking tunnels into account
Tunnels are defined by their internal and external contours (series of points/segments). They may intersect with a border between two layers with a taking into account of multiple tractions at the points of junction.
Module for estimation of structure-borne noise in building premises via a hybrid approach
The 2.5D approach used to predict vibration levels in ground and the structure of buildings is further completed in MEFISSTO by the introduction of 3D volumes in post-processing for acoustic radiation through walls and forecasting of structure-borne noise levels (2D3/4 approach). This approach has been validated by comparison with full 3D calculations.
MEFISSTO therefore performs a simulation over the entire chain of structural noise propagation, from the vibrations induced by the passage of rolling stock to the acoustic emission through the walls in a building.
The calculation of the mobility of tunnels measured during the passage of trains was correctly forecasted by MEFISSTO during the framework of Greater Paris construction sites. MEFISSTO equally served as a reference for studies on the vibrational impact over the ensemble of the project.
The 2.5D and 2D3/4 were validated in relation to 3D calculations.
Propagation of vibration in ground...