Discrete and non-discrete mixed methods applied to eigenvalue problems of plates

A mixed variational formulation for eigenvalue problems of plates is presented. Spline functions with multiple nodes are used to interpolate the displacement and moment fields. The solution procedure can be applied in either discrete or non-discrete forms. In contrast with displacement methods, the specified boundary conditions can be considered very easily by introducing multiplicity in the boundary nodes. Numerical examples include buckling and free vibration, of rectangular plates, with in-plane loading and or elastic foundations. The accuracy of the results obtained and the superiority of the mixed methods presented to conventional displacement approaches are discussed.