A method is presented to estimate the ultimate moment based on a simplified approach to represent the behavior of stiffened plate columns. The assessment of the strength of a very large crude carrier is performed and compared with the moment at failure in hogging estimated by other methods applied to the same case. The proposed method allows the prediction of the degradation of the strength due to corrosion and residual stresses. It also allows the evaluation of the strength of the hull at several heeling conditions. Finally, an analysis of the efficiency of the high tensile steel is carried out.