environmental vibrations and ground- structure by philippe
TRANSCRIPT
Environmental vibrations and ground-structure interactionby Philippe JEAN
General concepts
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MEFISSTOEnvironmental vibrations and ground-structure interaction
CSTB’S TOOL TO TACKLE ENVIRONMENTAL VIBRATIONS
ISSUES
> Predicts vibration and structure-borne noise in buildings
> Tunnels and multilayer grounds
> Ground-structure interaction
A CUTTING-EDGE CALCULATION METHOD
> Hybrid BEM/FEM formulation
> Vibration propagation calculated in 2.5D
> Structure-borne noise calculated by 3D modal coupling
EASE OF USE
> Generation of open files (text, GMSH)
> A Scilab package for pre- and post-treatment
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2.5D modelling
AN APPROACH WELL-ADAPTED TO RAIL APPLICATIONS
> Geometry defined in a 2D cut… (perpendicular to the rail)
> … but excitation defined in 3D (a set of points)
> 2.5D result obtained by integration over a set of 2D results
A NECESSARY APPROACH (COMPARED TO FULL 2D) …
… AND SUFFICIENT (COMPARED TO FULL 3D)
> Simplified geometry definition and meshing (2D)
> Much smaller CPU time
> Captures main physical phenomena
MEFISSTOEnvironmental vibrations and ground-structure interaction
P. Jean, C. Guigou, M. Villot, A 2,5D BEM Model for Ground-Structure Interaction, Building Acoustics,11(3), 1-17 (2004)
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Hybrid FEM/BEM method
FEM : FINITE ELEMENTS
> Field described using a discretization of the entire domain
> Adapted to finite domains only
> Can handle with complex and/or thin structures
BEM : BOUNDARY ELEMENT METHODS
> Description using the domain boundaries only
> Can handle infinite domains (ground layers)
FEM/BEM APPROACH
> Can easily handle all cases!
> For the end-user, just a switch (BEM/FEM) for each domain
MEFISSTOEnvironmental vibrations and ground-structure interaction
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Structure-borne noise calculationORIGINAL APPROACH 2D 3/4
> Post-treatment of 2.5D calculations
> Reconstruction of 3D acoustic volumes (finite depth)
> Calculation of the acoustic pressure field using SEA-like radiation
or modal coupling
> Approach validated against full 3D calculation
MEFISSTOEnvironmental vibrations and ground-structure interaction
2.5D geometry 3D geometry
P. Jean, A 2,75D Model for the Prediction of Noise Inside Buildings Due To Train Traffic, Acta Acust United Ac 104, 1009-1018 (2018)
Applications
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Urban train impact on future building
➢ Acquisition of the architectural data
and ground layers (geotechnical
study)
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Urban train impact on future building
➢ Source identification
• On site measurements➢ Different distances from track
➢ Measurement of the three components
• Mefissto calculation on initial site
• Tuning (damping factor, injected force
level…)
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Urban train impact on future building
2D vertical velocity level @ 50 Hz
➢ Calculation of the vibration
field for the future building
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Urban train impact on future building
➢ Impact of different isolation solutions
Initial (no solution) Screen Decoupling
Resilient
layer
level
Validations
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Comparison with 3D FEM
Tunnel – ground transfer case
Vibration levels at
surface
3D
FEM
2.5D model3D model
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Tunnel mobility
Tunnel mobility
➢ Impact force in the middle of the apron in a tunnel
➢ Measured mobility at several distances down the tunnel
(along the z-axis) and weighted average
➢ Effective mobility: ratio between velocity response [m/s] and
force density [N/m1/2]x
y
z
Eff
ecti
ve m
ob
ilit
y
[ m
.s-1
/ (N
.m-1
/2)]
Calculation
Measurement
E. Augis, M. Villot, P. Jean, C. Gallais, P. Ropars, C. Guigou-Carter. Vibration emission from railway lines in tunnel – part 1: characterization. In
Proceedings of ICSV23 in Athens (2016)
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Tunnel mobility
Tunnel mobility
➢ Impact force in the middle of the apron in a tunnel
➢ Measured levels on apron and on transverse wall
x
y
z
E. Augis, M. Villot, P. Jean, C. Gallais, P. Ropars, C. Guigou-Carter. Vibration emission from railway lines in tunnel – part 1: characterization. In
Proceedings of ICSV23 in Athens (2016)
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Ground-structure interaction
Ground-structure transfer function
➢ Difference of vertical vibration level
at different points
➢ Impact force on surface
How to set up a calculation ?
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Input dataBUILDING
> An architectural cut in DWG/DXF format or a simple description
➢ Clean up the file to keep relevant domain boundaries
➢ Define the different domains
GROUND
> Some data regarding the ground layers (geotechnical report)
➢ Find layer depths and type of materials (soft ? organic ? sandy ?)
➢ Get some typical parameters values (e.g. in provided database) and tune them to fit measurements if
possible
SOURCE
> Some data regarding the source
➢ Measured vibration levels (recommended)
➢ Force density (N2/m per third-octave)
MEFISSTOEnvironmental vibrations and ground-structure interaction
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Model dataGEOMETRY
> Can be generated using the Scilab package from a DXF file
DOMAINS
> Calculation method: BEM or FEM
> Material parameters: density, Young’s modulus, Poisson’s ratio, damping coefficient
SOURCES AND RECEIVERS
> Position of point sources (2 components in 2D - 3 components in 2,5D)
> Receivers points or zones (can include acoustic volumes)
TYPE OF RESULTS
> Calculation of the velocity field or structure-borne noise (acoustic volumes)
> Results: spectral values or maps (GMSH format)
MEFISSTOEnvironmental vibrations and ground-structure interaction
Demo
Mefissto in practise
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Mefissto in practiseCORE: TWO HIGHLY-OPTIMIZED EXECUTABLE FILES
> mefissto : runs 2D and wavenumber calculations
> integre_kz : 2.5D wavenumber integration
A SCILAB PACKAGE FOR PRE-TREATMENT AND POST-
TREATMENT
> Developed within a free numerical calculation environment:
Scilab/GMSH
> Pre-treatment: writes geometry from DXF, checks input files,
checks meshes
> Run calculations: possibility to parallelize over frequencies
> Post-treatment: reads output files, plots, third-octave
integration…
MEFISSTOEnvironmental vibrations and ground-structure interaction
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Provided documentation
USER MANUALS
> Starter guide and modeling guide (in progress)
> Scilab package functions description
> A set of documented examples with input files and results
> A comprehensive description of Mefissto input file format
MATERIAL DATABASE
> Provides typical values of material parameters,
for ground layers and structures
MEFISSTOEnvironmental vibrations and ground-structure interaction
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Short term evolution
MODULE FOR SOURCE CALCULATION: VIBRAFER1
> Simplified model of train track system
> Input: train unsprang mass, train speed, track component
parameters, rail unevenness
> Output: injected force spectrum (input to Mefissto)
MEFISSTOEnvironmental vibrations and ground-structure interaction
1 M. Villot, E. Augis, C. Guigou-Carter, S. Bailhache, C. Gallais, P. Jean. Vibration emission from railway lines in tunnel – part 2 : prediction. In ICSV23 in Athens (2016)
Get MEFISSTO
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Get MEFISSTO
Full purchase : 19 500 € excl tax
➢ Life-time license for 1 computer
➢ 2 days initial technical training by MEFISSTO experts
➢ Free maintenance for 1 year
➢ Free remote technical support for the 1st year : 16 hours maximum
Maintenance and technical support after 1 year of acquisition :
1 950 € excl tax / year
➢ Software maintenance including update
➢ Remote technical support : 8 hours maximum / year
SOFTWARE ACQUISITION
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IN-HOUSE EXPERT CONSULTING OR SUBCONTRACTING
Get expertise around MEFISSTO
Subcontracting : from 2 500 € to 10 000 € excl tax per analysis
> varies depending on the study purpose and
input data
➢ Various input data:
❖ 2D vertical cuts
❖ Soil description
❖ Vibration measurements / force density
➢ Type of results:
❖ Vibration levels
❖ Structure-borne noise levels
❖ 2D maps of vibration levels
Contact : Alexandre JOLIBOIS
[email protected] / +33 6 66 63 17 02
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Merci pour votre attention