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www.sname.org/sname/mt April 2012loads due to explosions; impact loads asso- ciated with collision, grounding, or dropped objects; and such age-related degradation as corrosion, fatigue cracking, and local denting damage. ese phenomena occur in di erent sce- narios and involve di erent mechanisms, but it is interesting to note that they all commonly give rise to nonlinear structural consequences that involve both geometric and material nonlinearities. To eliminate human error caused by a lack of knowl- edge, it is thus essential that the nonlinear structural consequences associated with such phenomena be accurately and effi- ciently identi ed. Paradigm change Although the maritime sector has devoted substantial effort to applying advanced design approaches, the shipbuilding industry traditionally employs classi ca- tion society rules for the design of trading ships, and the o shore industry applies rst- principles methods based on limit states to a greater extent. e design approach for moored ship-shaped offshore structures for oil and gas developments in deep waters, such as oating, production, storage, and offloading units, can be described as a fusion of the two industry approaches. Traditional design approaches are based primarily on design formulations or closed-form expressions, in addition to past experience, and are likely to be deterministic in nature. e application of mathematical algorithms is considered sufficient to identify actions and action e ects, which are likely to be operational in nature. For the nonlinear structural consequences arising from extreme or accidental phenomena, however, deter- ministic approaches based on design formulations inevitably involve a high degree of uncertainty, thus introducing the risk of human error associated with engi- neering factors. To reduce such error at the structural design stage, it is recommended that probabilistic approaches based on rst principles and engineering technologies be applied in association with limit states and risks. Experimental investigations carried out on full- or at least large-scale models, in addition to more re ned algo- rithms, are also necessary to identify more accurately the nonlinear structural conse- quences arising from extreme or accidental phenomena. MTJeom Kee Paik is a professor in the Department of Naval Architecture and Ocean Engineering of Pusan National University in Korea. LESSONS LEARNED LEARNED Rough sea conditions can amplify hull girder loads to the extent that they reach or even exceed the corresponding design values. + On January 13, 2012, the cruise ship Costa Concordia partially sank after grounding o the coast of Italy.