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$$$$ FRONABS  NOTICE  CHAT      11/09/12    21:16:20     7124           
                                             DATE     11/09/12
                                             
  Procedure FRONABS                         Voir aussi :
   -----------------   
   RIG1  =  FRONABS  TAB1  ( TYP_FRON ) NHARM   




Description :
-------------

The FRONABS procedure makes it possible to create absorbing
boundaries of LYSMER or WHITE type used in the calculations 
of the ground-structure interaction. These boundaries which 
are composed of viscous dampings aim at avoiding, as best as
possible, the wave reflection on the edge of the mesh at the 
ground :

    - the LYSMER type boundary absorbs all the energy of the plane
      waves with normal incidence. It is used in the deconvolution
      of the ground seismic motion;

    - the WHITE type boundary ensures an optimum energy absorption
      efficiency when several waves come with different angles of
      incidence at the same time.

                                                                               
Contents :                                                                    
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Input data :
-----------                                                                    
                                                                              
 TAB1 :   TABLE  containing the following indices in letters

'FRONTIERE' : boundary geometrical support, composed of SEG3 type 
              elements either horizontal or vertical in 2D : 
              PLANDEFO, AXIS, FOUR 0,1  
                     
'MASSE_VOLUMIQUE' : ground density
'POISSON'         : Poisson's ratio of the ground
'YOUNG'           : Young's modulus of the ground


 TYP_FRON  : MOT indicating the type of boundary used :  
            'LYSMER' (by default) or 'WHITE'. 
                               
 NHARM : ENTIER  number of harmonics in case of MODE FOUR 
         option ( 0 or 1 )


Output data :
-----------

RIG1 : 'RIGIDITE' type object of 'AMORTISSEMNT' subtype
        containing the damping matrix of the absorbing boundary


Note :
--------
                
         The procedure neither deals with oblique boundaries 
         nor with three-dimensional models.



 
 

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