Design and Evaluation Based on Excessive-Acceleration Mode Analysis Applying IMO Second-Generation Intact Stability Criteria for Ships

초록

This study evaluated excessive-acceleration vulnerability based on the Level 1 and Level 2 criteria of the IMO second-generation intact stability framework. A 13K oil chemical tanker was analyzed, incorporating wave-induced dynamic effects into the assessment. The comparison between Level 1 and Level 2 results showed that the Level 2 criterion provided a less conservative evaluation, allowing a wider acceptable range of vertical positions relative to the roll axis. This highlights the necessity of dynamic analysis under realistic wave conditions. To improve the accuracy of the evaluation, the Froude-Krylov roll moment was reformulated by incorporating diffraction effects. Unlike conventional approaches that consider only incident-wave excitation, the proposed method accounts for both incident- and diffracted-wave components. This results in a smoother frequency-dependent effective wave slope function and a more consistent representation of hydrodynamic excitation. The results demonstrate that including diffraction effects extends the allowable range satisfying the Level 2 criterion, thereby increasing the design margin associated with the vertical center of gravity. Although the proposed approach requires additional computational effort, it provides a basis for examining the influence of diffraction on excessive-acceleration assessment.

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