Second Generation Intact Stability Criteria - Robustness and Consistency Analysis

The formulation of the Second Generation of Intact Stability Criteria was finalized by the International Maritime Organization (IMO) in 2020. The criteria have been developed for a future incorporation into the 2008 IS Code, however they require testing before using them as a mandatory criterion. Member states are by IMO invited to use the Interim Guidelines and report back the experience. The criteria are formulated for five failure modes, each of which is analyzed by two vulnerability levels and, if needed, a direct numerical simulation. The present paper summarizes results testing the vulnerability levels in these new stability criteria. The calculations are carried out for 17 ships using the full matrix of operational draughts, trims and GM values. Each failure mode criterion is examined individually regarding construction of a GM limit curve for the full range of operational draughts. The consistency of the outcomes has been analyzed, and finally examined whether the new criteria tend to be more or less conservative compared to the present rules by evaluating approved loading conditions. The analyses were performed in 2016 and based on criteria developed in 2015 and 2016 and amended by the Sub-Committee on Ship Design and Construction of IMO. Work performed in IMO up to Spring 2020 relevant for the analysis is described.