Postbuckling instability analysis of shells using the mixed method

The paper deals with a method to calculate stable pre- and postbuckling behaviour of thin shells. First some features of the used mixed shell element, with displacements and stress resultants as nodal unknowns, are outlined and discussed. Second a quasi viscous strategy is presented, which allows to pass unstable regions and limit points. The approach uses variable ficticious damping. With the load applied all at once, stable equilibrium states are approached without step by step, incrementation. Examples are given for the buckling of cylindrical shells. (orig.)