Hybrid Framework for Reliability-Based Design Optimization of Imperfect Stiffened Shells

Variations of manufacturing process parameters, environment aspects, and imperfections may significantly affect the quality and performance of stiffened shells. The reliability-based design optimization (RBDO) of stiffened shells, considering all these uncertainty factors simultaneously, is extremely time-consuming, even if the surrogate-based technology is used. Therefore, a hybrid bi-stage framework for RBDO of stiffened shells is presented to release the computational burden, where two main sources of uncertainties are considered: variations of material properties and geometric dimensions are described as random variables, while various forms of imperfections of stiffened shells are covered by the single perturbation load approach. The basic idea of the proposed method is to combine the efficiency of smeared stiffener method with the accuracy of finite element method, and then narrow the design window efficiently with little accuracy sacrifice. The adaptive chaos control method is used to ensure the robustness of the search process of the most probable target point. The numerical example illustrates the advantage of the proposed method over other RBDO approaches from the point of view of computational cost, accuracy and robustness of the result.