Abstract: The subject of the disclosed embodiments is a method of optimizing stiffened panels under stress. In particular, the method makes it possible to determine the stress distribution in stiffened panels with postbuckling taken into account. The method proposed is a coupling between an overall, linear stress calculation approach, based on strength-of-materials results, and a local, nonlinear approach for the behavior of the stiffened panel. The disclosed embodiments fall within the field of aeronautical design, at the pilot study stage in the definition of a civil transport airplane of conventional architecture.