IMPERFECTION SENSITIVITY ANALYSIS AND OPTIMIZATION OF HIERARCHICAL STIFFENED SHELLS WITH T-SECTION STIFFENERS

Abstract

Post-buckling analyses of four types of axially compressed stiffened shells were carried out using the explicit dynamic method. The considered stiffened patterns include the uniform stiffened shell, the bidirectional hierarchical stiffened shell with rectangle-section stiffeners, and unidirectional and bidirectional hierarchical stiffened shells with T-section stiffeners. The entire load vs. end-shortening curves of the four stiffened shells were obtained. Then, taking the mode shape as an illustrative imperfection, it is found that the bidirectional hierarchical stiffened shell with T-section stiffeners is relatively insensitive to imperfections and shows outstanding designability characteristics. Afterwards, the imperfection sensitivities and corresponding post-collapse stable equilibrium paths of the four stiffened shells were compared. A certain degree of consistency is found between the two types of results. This indicates that both the load-carrying capacity and imperfection sensitivity can be obtained only by a single post-buckling analysis of the structure with perfect geometry, which can remarkably reduce the computational time needed for structural design including imperfection sensitivity. Finally, an optimization framework for hierarchical stiffened shells with T-section stiffeners to achieve low imperfection sensitivity was proposed, and the illustrative example demonstrates that a more robust optimum design can be achieved efficiently.