| The rational FEM formulation, which is quite different from the usual FEM formulation, is proposed here. The methodological difference is that the rational FEM emphasizes the PDEs of the problem and use its solutions to approximate the internal fields of the element. The methe matical derivation is guided by the characteristics of the problem, i. e. object oriented. The rational plane 4-node element (RQ4) is derived for demonstration. Numerical results demonstrate the superiority of the rational FEM. |