Triangular thick plate stiffness matrix transformation

Ronankeating

Hi community member,

Regarding the book that I'm reading original writer has used Ni = ai + bi*x + ci*y shape function for the formulation of stiffness matrix for thick triangular plates.

The writer has not mentioned in the article that the resulting stiffness matrix is required to be transformed to global coordinates. What arised my suspicion was, in the illustrations local 1-2 edge of triangle is always aligned to global X-axis. Is it coincidental or "must" to perform the transformation to that specific shape function?

If transformation is required at all to match the exact illustrations, how should be performed, I mean how to choose the base point for rotation, rotation around any arbitrary vertex will work ?


Best Regards,

Ronankeating

Any comment will be appreciated!