A new concept of optimization for postbuckling behaviour

In this paper geometrically nonlinear structures are optimized against instability. The postbuckling analysis performed for structures optimally designed for only buckling constraints shows that in many cases their behaviour after buckling is unstable. That is a weakness of the design and therefore, the alternative design philosophy is proposed, in which the postbuckling analysis is implemented directly into the formulation of optimization problem. As the result the modified optimal structure is created, for which previously unstable behaviour becomes stable. The effect of modification of postbuckling behaviour in most of the known cases has been obtained by changing sizing variables. In this paper a new approach is proposed, namely stabilization of the postbuckling path is obtained by application of additional forces acting on the optimized element. Numerical results are presented for the design of finite-degree-of-freedom systems that model the behaviour of real elastic frame and shell structures.