In [45] an intact stability criterion was developed which aims at the determination of suffcient intact stability of a ship in heavy weather. The aim of this dynamic intact stability criterion was to establish a minimum level of stability which should ensure that the remaining capsizing risk in heavy wether shall be as low as reasonably possible. The proposed criterion results in the computation of an index value (the insuffcient stability event index ISEI). To make the criterion practically applicable, threshold values need to be defined for this index to distinguish between safe and unsafe ships or conditions on the one hand and to establish a required minimum level of safety in heavy weather on the other.To establish such a threshold value for the ISEI, we have investigated several full scale capsizing events with appropriate numerical methods and procedures. These methods or procedures are based on the direct computation of the non linear roll motions of the ship in time domain in a natural (short crested irregular) seaway [74], [27]. Such kind of methods or procedures have been developed during several decades with the special intention to analyze full scale capsizing events for German authorities.
