I have some problems with my matlab code in a 9 node shell
element each node has 5 DOFs. I found that stiffness matrix for each
element is symmetric, but after transformation to global coordinate
system, the transformed stiffness matrices and the resulted global
stiffness matrix of entire shell is nonsymmetric, where order of
transpose([k]) -[k] is approximately E-18.
Mass matrix also has
been antisymmetric after transformation and so I can't solve
characteristic equation to find eigenvalues needed for dynamic analysis.
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