A Study On Criteria Of Dead Ship Stability

International shipping market demand a higher level of high-technicality and high-safety of the vessels, people are paying more attention to the intact stability of ships. According to the character of stability failure, IMO divides stability failure modes into five parts. Stability criterias of dead ship will be implemented by three levels: vulnerability criteria and direct stability assessment. On the basis of the latest drafts, the following contents are mainly introduced:(1) Statistical linear method: First, the details about statistical linear method is analysed, and the corresponding program is developed. Then, the reliability of program is confirmed by taking the CEHIPAR2792 as an example, and the effects of three different methods for calculating effective wave slope on capsizing probability are validated.(2) Piece-wise linear approach: First, the details about piece-wise linear approach is analysed, and the corresponding program is developed. Then, the reliability of program is confirmed by taking the CEHIPAR2792 as an example, according to the calculating results, the paper compares the piece-wise linear approach with statistical linear method and Monte-Carlo simulation.(3) Sample vessels calculations: the standard values of level 2 vulnerability criteria for dead ship have not been decided in the latest drafts. First, the calculating procedure of stability criteria of dead ship is explained detailly with CEHIPAR2792. Then, the applicability and reasonability of the vulnerability criteria are analyzed. Finally, the paper gives the advice on the revised criteria values, which is for the sake of keeping consistent on every level of stability criteria.(4) Dead ship stability test: the thesis takes a tuna vessel as a model, and the model is restrained with a counter weight. First, the roll damping is obtained by decay test at zero speed. Then, roll motions are obtained with different beam winds and waves conditions, considering the effects of different initial heeling angles on roll motions, which strongly support the study of direct stability assessment in this thesis.(5) Direct stability assessment: the method of direct assessment is also being developed by IMO second generation intact stability expert group. First, one uncouple mathematical model is developed. The program is built by taking the tuna vessel as an object of study and the roll motions are predicted in beam winds and waves. Then, the capsizing probabilities are calculated with Monte-Carlo simulation, considering different initial heeling angles, and the practicability of 1DOF direct stability assessment is verified by comparing with the statistical linear method.