I'm trying to better understand the 3-noded triangular element with drilling rotations.
I think that the 3-noded triangle with drilling rotations is derived from the 6-noded linear strain triangle by, for mid-side nodes, constraining out-of-plane dof & converting in-plane dof to nodal rotation.
In particular, I'm wondering about the following:
1) Whether strains are constant (like 3-noded CST) or vary (like 6-noded LST) within the element ? Some of the literature seems to refer to constant strain (from translational dofs) & higher order strain (from rot'n nodes) being superimposed.
2) How the nodal rotations are obtained since tracking only 3 corner nodes ? I think that they must be calculated in some way, perhaps from the relative deflections of the corner nodes.
Any thoughts are very welcome !
Thanks, John.