Optimum design of shell structures with stiffening beams

The optimum design of stiffened shell structures is investigated using a robust and efficient optimization algorithm where the total weight of the structure is to be minimized subject to behavioral constraints imposed by structural design codes. Evolutionary algorithms and more specifically the evolution strategies (ES) method specially tailored for this type of problems is implemented for the solution of the structural optimization problem. The discretization of the stiffened shell is performed by means of cost-effective and reliable shell and beam elements that incorporate the natural mode concept. Three types of design variables are considered: sizing, shape, and topology. A benchmark test example is examined where the efficiency and robustness of ES over other optimization methods is investigated. Two case studies of stiffened shells are subsequently presented, where a parametric study is undertaken to obtain the most efficient design compatible with the regulations suggested by design codes such as Eurocode. The important role of the stiffeners and how they can be optimally chosen to improve the performance of shell structures in terms of carrying capacity and economy is demonstrated.