A new family of locking-free finite elements for shear deformable
Reissner-Mindlin plates is presented. The elements are based on the
"tangential-displacement normal-normal-stress" formulation of elasticity. In
this formulation, the bending moments are treated as separate unknowns. The
degrees of freedom for the plate element are the nodal values of the
deflection, tangential components of the rotations and normal-normal components
of the bending strain. Contrary to other plate bending elements, no special
treatment for the shear term such as reduced integration is necessary. The
elements attain an optimal order of convergence