Multi-objective optimization of orthogonally stiffened cylindrical shells using optimality criteria method

A multi-objective optimality criteria (oc) is used to obtain optimum design of metal cylindrical shells under combined external loading. the objectives are to maximize the axial and hoop stiffness and minimize the mass of stiened cylinders subject to the constraints, including functions of weight and buckling load, in such a way that the stiffened shell has no increase in weight and no decrease in buckling load, with respect to the initial unstiened shell. the optimization process contains six design variables, including shell thickness, number of circular ring stieners, number of longitudinal stringer stieners, height of ring stiffeners, width of ring stiffeners, and longitudinal stiffener eccentricity from the shell centerline. in the analytical solution, the rayleigh-ritz energy procedure is applied and the ring stiffeners are treated as discrete elements. the shapes of the ring and stringer stiffeners are assumed rectangular and z, respectively. the shell is subjected to uniform axial and non-constant external pressure, simultaneously. the longitudinal stringers are placed in equal spacing, whereas the rings can be placed in an unequal space, due to the non-constant of external pressure over the cylinder length. the results show that the iteration numbers depend on the ring stiffener space states.