Encounter frequency effect on the simplified design criteria against parametric roll

Abstract The development of the second generation intact stability criteria is ongoing in the International Maritime Organization, and the level 1 and 2 criteria are almost agreed. However, validation/verification studies of the level 2 criteria remain to be insufficient. Herein, the mean frequencies of Grim's effective waves are used and compared with the draught of the second check of the level 2 criteria for parametric roll. Therefore, the encounter frequency assumption used in the draught second check is verified. Additionally, it is shown that the number of samples of operational conditions should be at least 24.