NEW STRESS RECOVERY FORMULA FOR B-BAR METHODS

An alternative justification of the B-bar procedure using the Hu-Washi zu variational principle is presented. In contrast to previous work, t he derivation starts from the three groups of algebraic equations (str ain-displacement equations, stress-strain equations and equations of e quilibrium) obtained by discretization of the Hu-Washizu functional. B ased on an appropriate assumption, these equations can be manipulated to yield the element stiffness matrix in the form typical of the B-bar procedure. This approach directly leads to a stress-recovery formula different from the one suggested before. The theory is illustrated by application to a family of quadrilateral plane elements.