The fundamental principal of load bearing analysis is the perturbation energy concept. It allows for an evaluation of the sensitivity to imperfections and an identfication of realistic structural and kinetic limit loads.
Example: Buckling of Shells - Eigenmode under axial and radial loading, verification of the model
Fundamental idea of the perturbation energy concept is the identification of a critical mode related to a limited stable basic mode. The difference of energy between these two states is specified as perturbation energy. The corresponding load, which is necessary to proceed from the basic mode to the critical mode, is known as perturbation load. Besides a qualitative comparison of the sensitivity to imperfections of different basic modes this concept allows for an evaluation of different standards for buckling analysis of shell structures.
In spite of the profound nonlinear strucutral behaviour of prestressed membranes design and analysis of those structures are state of the art. An finite element concept that considers the wrinkling on element level by the use of particular shape functions provides discretisation-independent calculation results even at a loss of prestress.
Example: Airbag
Even with a small number of elements the difference between the calculated deformation of an equilibrium state and the reference solution amounts only a few percent.
S. Kern: Stabilität von ausgesteiften, zusammengesetzten Rotationsschalen.