Deformation decomposition for a plate element

The stiffness matrix of a square plate element from the analytical integration is decomposed into its eigenvalues and corresponding eigenvectors, with the latter representing the nonzero-strain deformation modes, and the eigenvalues representing the stiffness corresponding to the standardized deformation modes. The whole deformation of an element in a plate under external loading can be decomposed as the weighted summation of the nonzero-strain deformation modes together with certain rigid modes. Based on the deformation decomposition of the element, the inherent nature of deformation on the plate is investigated. A simply supported square plate under a central vertical static load is presented for illustration.