IMPROVED ENHANCED STRAIN FOUR-NODE ELEMENT WITH TAYLOR EXPANSION OF THE SHAPE FUNCTIONS

A class of enhanced strain four-node elements with Taylor expansion of the shape function derivatives is presented. A new concept of enhancement using besides the `standardʹ enhanced strain elds also two other enhanced elds is developed on the basis of the Hu{Washizu principle. For rst-order Taylor expansion enhanced modes become uncoupled, thus only a negligible amount of computing e ort for the static conden- sation of enhanced modes is needed. Furthermore, the formulation permits a symbolic integration, which leads to a closed-form solution for the element tangent matrix. Several numerical examples show that the element is stable, invariant, passes the patch test and yields good results especially in the highly distorted regime.