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4.1  FE mesh declaration

This section gives a summary of FE mesh declaration with pointers to more detailed documentation.

4.1.1  Direct declaration of geometry (truss example)

Hand declaration of a model can only be done for small models and later sections address more realistic problems. This example mostly illustrates the form of the model data structure.


Figure 4.1: FE model.

The geometry is declared in the model.Node matrix (see section 7.1 and section 7.1.1). In this case, one defines 6 nodes for the truss and an arbitrary reference node to distinguish principal bending axes (see beam1)

 %     NodeID  unused   x y z
 model.Node=[ 1      0 0 0    0 1 0; ...
              2      0 0 0    0 0 0; ...
              3      0 0 0    1 1 0; ...
              4      0 0 0    1 0 0; ...
              5      0 0 0    2 0 0; ...
              6      0 0 0    2 1 0; ...
              7      0 0 0    1 1 1]; % reference node

The model description matrix (see section 7.1) describes 4 longerons, 2 diagonals and 2 battens. These can be declared using three groups of beam1 elements

 model.Elt=[ ...
  % declaration of element group for longerons
  Inf     abs('beam1') ; ...
  %node1  node2   MatID ProID nodeR, zeros to fill the matrix 
    1       3      1    1     7       0 ; ...
    3       6      1    1     7       0 ; ...
    2       4      1    1     7       0 ; ...
    4       5      1    1     7       0 ; ...
  % declaration of element group for diagonals
  Inf     abs('beam1') ; ...
    2       3      1    2     7       0 ; ...
    4       6      1    2     7       0 ; ...
  % declaration of element group for battens
  Inf     abs('beam1') ; ...
    3       4      1    3     7       0 ; ...
    5       6      1    3     7       0 ];

You may view the declared geometry

 cf=comgui('guifeplot -project "SDT Root"',3); % Robust open in figure(3) 
 cf.model=model;       % create feplot axes
 fecom(';view2;textnode;triax;'); % manipulate axes 

The demo_fe script illustrates uses of this model.


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