IMPROVED TRANSVERSE SHEAR STIFFNESSES FOR LAYERED FINITE ELEMENTS.

Finite elements with C**0-continuity conditions need the transverse shear stiffness to couple translational and rotational displacements. Accurate stiffness values must account for a realistic shear stress distribution, in particular if the considered structure is layered. Integrating the equilibrium conditions leads to shear stresses as functions of membrane force and bending moment derivatives, which can be replaced by transverse shear forces if cylindrical bending states are assumed. These functions are used in the complementary energy density to determine improved stiffnesses. For homogeneous material they correspond with Reissner's correction factor of 5/6 as applied to shear modulus times thickness. Isotropic layers, however, show correction factors between 0. 45 and 1. 0 depending on the layer thickness and modulus ratios. The proposed formulation covers orthotropic material as well as sandwich constructions. Therewith, different versions of layered and sandwich elements become obsolete.