A GEOMETRICALLY NONLINEAR CURVED SHELL ELEMENT WITH CONSTANT STRESS RESULTANTS

A curved triangular shell element with constant stress resultants and 12 degrees of freedom is presented. The degrees of freedom are the displacement components in the vertices and the rotations about the element sides. The starting point is the combination of a constant strain triangle and a flat constant bending triangle. The membrane deformations of this original flat element are modified, so that curvature changes give an essential contribution in the geometrically nonlinear regime. Initial curvature is brought into account by observing initial deflections of the flat element with modified membrane deformations. Arbitrary rotations are incorporated by means of co-rotation theory, applied to the bending behaviour only. Unconventional equivalent nodal forces for pressure loading are discussed, which are more effective than work equivalent nodal forces in cases where the loading is mainly carried by membrane forces and coarse meshes are used. The performance of the proposed element is compared with state-of-the-art elements, known from the literature.