A mixed element for geometrically and physically nonlinear shell problems

A triangular element for geometrical and physical nonlinear shell problems is described. The degrees of freedom are 18 displacement components and 6 rotation-like scalars. A key role in the description is played by a flat reference triangle through the vertices of the element. The governing equations are derived by means of the principle of virtual work, using constitutive equations based on a layered model. The performance of the element is illustrated by two sample problems.