Numerical stability for a dynamic Naghdi shell

We consider an elastic model for a shell incorporating shear, membrane, bending and dynamic effects. We make use of the theory proposed by Arnold and Brezzi [1] based on a locking free non-standard mixed variational formulation. This method is implemented in terms of the displacement and rotation variables as the minimization of an altered energy functional. We extend this theory to the shell vibrations problem and establish optimal error estimates independent of the thickness, thereby proving that shear and membrane locking is avoided. We study the numerical stability both in static and dynamic regimes. The approximation schemes are tested on specific examples and the numerical results confirm the estimates obtained from theory.