Efficient Optimization of Cylindrical Stiffened Shells with Reinforced Cutouts by Curvilinear Stiffeners

An efficient optimization framework of cylindrical stiffened shells with reinforced cutouts by curvilinear stiffeners is proposed in this study. First, an adaptive method to determine the near field around the cutout and far field away from the cutout is presented. Then, a novel hybrid model is established to reduce the computational efforts of postbuckling analysis; the numerical implementation asymptotic homogenization method is used to smear out the stiffeners in the far field, and curvilinear stiffeners are adopted to improve the loading path and thus local stiffness of the near field, which can provide a type of flexible stiffener configurations for cutout reinforcement. After that, the optimization of curvilinear stiffeners is performed by a novel bilevel strategy based on the hybrid model. In the first level, a stiffener distribution function is used to reduce the number of active variables, and then stiffener layout, stiffener number, and section profile are optimized simultaneously. In the second level, the stiffener number and section profile are held constant, and local optimization is then performed for each curvilinear stiffener location. An illustrative example demonstrates the effectiveness of the proposed framework, when compared with traditional optimizations.