ABSTRACT
ABSTRACT: One approach to formulating geometrically nonlinear shell finite elements is to accept the linear formulation as representative of shell behavior and upgrade it to a nonlinear shell element using the perturbation method. Load perturbation of the linear discrete equilibrium equations of an element in its global coordinate system leads to the well established definition of the geometric stiffness matrix as the gradient of the nodal force vector when the stresses are held fixed. This approach has been successfully applied to trusses, space frames, membranes and thin isotropic shells.
