One-Compartment Damage Survivability Versus 1992 IMO Probabilistic Damage Criteria for Dry Cargo Ships

Abstract

No international or U.S. Coast Guard requirements for the damage survival of dry cargo ships existed until February 1992, when an international, probabilistic damage standard for dry cargo ships was adopted by the International Maritime Organization (IMO) and the U.S. Coast Guard. A deterministic one-compartment damage standard has been applied to most U.S.-flag dry cargo ships built since 1937, either voluntarily or as a requirement for Federal assistance under the Maritime Administration. Despite some of its inherent deficiencies, it appears that the one-compartment standard has invariably resulted in the construction and operation of cargo ships whose damage survivability considerably exceeds the minimum survival criteria of the new IMO rules. Some weaknesses in the IMO damage rules are discussed and modifications suggested. The results of sensitivity studies incorporating proposed modifications are presented for a sample of U.S.-flag cargo ships. An evaluation of results suggests that the IMO rules in some instances may not go far enough in precluding unsafe ship design or operating practices; however, the proposed modifications will generally achieve much closer agreement between the survival requirements for these two methods. It is recommended that the proposed rules be modified to reflect a more rational approach in accordance with commonly accepted naval architectural practices, and to assure the highest level of damage survivability that is economically feasible.