1. Introduction
1.1 Background of study
1.2 Current status of IMO Second Generation Intact Stability Criteria study
2. Vulnerability to stability loss mode
2.1 Pure loss of stability
2.1.1 Vulnerability criteria in pure loss of stability (level 1)
2.1.2 Vulnerability criteria in pure loss of stability (level 2)
2.2. Parametric roll
2.2.1 Acceptance equation of parametric roll stability (level 1)
2.2.2 Acceptance equation of parametric roll stability (level 2)
3. Example of Korean Ship Stability Vulnerability Mode Calculation
4. Summary and conclusion
In order to prevent the loss of life and cargo due to the occurrence of various marine accidents, the IMO is developing the second generation of stability criteria to improve the stability of ships, which will ensure that a ship has sufficient stability even in waves. The new stability criteria are in addition to the existing stability criteria, which will remain in effect even after the new stability criteria are put in place.
Regarding the stability in waves, the criteria for five modes are being developed. The inspection structure is composed of a multi-layer structure to minimize the calculations used to verify whether or not the stability criteria are satisfied. The calculations to verify the criteria have been minimized. That is, at a low level, the criteria are verified by simple calculations, and as the level becomes higher, more complicated and detailed verification is performed. If the criteria are satisfied at the low level, the calculation for the next level is not performed. In general, because the lower level involves a greater design margin, vulnerabilities are conservatively assessed and the assessment results are unfavorable for optimization.
At level 1, which is the lowest level, the stability is assessed in a very simple way. However, at level 2, a more complex method is introduced to assess the stability by determining the probabilistic vulnerability.
Level 3 performs very detailed calculations by performing direct simulations, but this level requires a program with a high level of calculation. The specifications for this calculation program are under discussion. However, in general, a reasonable computer program requires a relatively long calculation time, and thus the development of a technique for determining the stability of a ship within a practical time is required.
When reviewing the results of applying the second generation of stability criteria to the previous ships built in Korea in various cases, it seems that the ships built under the current criteria do not meet the stability criteria in many cases and there is no choice but to operate the ships in a state where the ship speed, dead weight capacity, and other factors are limited. Therefore, it is considered that appropriate design changes are needed to meet the new stability criteria.