How do you perform structural optimization for minimum weight aircraft structures?

Structural optimization involves: Problem formulation (objective: minimize weight; constraints: stress, buckling, displacement, fatigue life, flutter); Sizing optimization of member thicknesses, stiffener dimensions; Shape optimization for hole shapes, fillet radii, interfaces; Topology optimization for load path identification in fittings; Composite layup optimization including ply thicknesses, orientations, stacking sequence; Gradient-based methods (sensitivity analysis) for large-scale problems; Global methods (genetic algorithms) for discrete variables like ply counts. Practical considerations: manufacturing constraints, discrete gauge availability, minimum gauges, and validation of optimized designs. Modern tools (OptiStruct, NASTRAN SOL200, Tosca) integrated with FEM enable practical optimization of production structures.