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FEA - Rotation Matrix of Angular Deflection

  1. Apr 13, 2012 #1
    I am trying to use FEA with space frame element. I know that for rotating an angle a around the z-axis, the translational displacements of the local and global coordinates are related through the rotation matrix:

    [tex]\begin{bmatrix}cos(a) & sin(a) & 0 \\ -sin(a) & cos(a) & 0 \\ 0 & 0 & 1\end{bmatrix}[/tex]

    But how about angular displacement (deflection), I thought the rotation matrix for them would be:

    [tex]\begin{bmatrix}1 & 0 & 0 \\ 0 & 1 & 0 \\ 0 & 0 & 1\end{bmatrix}[/tex]

    But it turns out it is the same with the first rotation matrix (or is it not?). Can anyone give me some hints how to derive or verify this?
  2. jcsd
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