TRIANGULAR THIN SHELL FINITE ELEMENT: LINEAR ANALYSIS.

The formulation of the linear stiffness matrix for a doubly-curved triangular thin shell element, using a modified potential energy principle, is described. The strain energy component of the potential energy is expressed in terms of displacements and displacement gradients by use of consistent strain-displacement equations due to Koiter. The element inplane and normal displacement fields are approximated by complete cubic polynomials. These functions satisfy neither the interelement displacement admissibility conditions nor the criterion of zero strain energy under rigid-body-motion. The former is met in the global representation by imposition of constraint conditions on the interelement boundaries; the constraints represent the modification of the potential energy. Errors due to the nonzero strains under rigid body motion are shown to be of small importance for practical grid refinements through performance of extensive comparison analyses. 46 refs.