The Study On Semi-submersible Vessel Loading And Sailing Safety Theory And Its Application

This dissertation mainly studies on the safety problems of the semi-submersible ship carrying the huge heavy cargo, which is based on the comprehensive investigations and analysis. This work belongs to transportation safety field under transportation planning and management discipline. This dissertation puts forward the semi-submersible vessel safety theory based on summing up the domestic and foreign scholars in this field, and applied the theory to practice.After summarizing and analyzing research on ship safety theory, semi-submersible ship's transport safety and other related areas, I found that the different stability criterion had different requirements to stability of load and unload, stability criterion usually had constrain to semi-submersible ship during the process of load and unload and ignored the navigation safety. It was lack research about the mechanism and application of safety factors. On these issues, this paper carried out the following studies:1 To the different stability requirement in different stability criterion, the key factor affecting the safety were found out in the shelter or open sea. Then based on the theory of dynamic balance, static balance, and other parametric roll, the semi-submersible metacentric height formulas applying to different conditions were deduced. The influencing factors and their mechanisms were explored by the formulas. Calculation case verified that the formula for metacentric height was reasonable.2 To the lack of stability criterion for navigation safety, the ship model based on roll and heavy was used to simulated the nonlinear rolling and found the key factor which affect the parametric rolling happen or not. The range of safety value was gotten to avoid parametric rolling.3 To the lack of application search, The influencing factors were found by the safety theory in load and unload, the formula for metacentric height was used to analyze the relation of metacentric height and safety factors. For the navigation safety theory application, the safety speed was used to solve the economical speed. A integrated optimization model of cargo distribution and ship speed was built, this model considered the influence of different fuel consumption of semi-submersible vessel with full-load and no-load on heavy cargo. A global search method based on an insertion method and an improved recursive smoothing algorithm was design. The results of an application example show that the method can reduce the transportation cost.Finally, the research results on semi-submersible vessels safety problems in process of loading and transportation were summarized. Taking into account the safety theoretical system was imperfect, a several representative research direction were proposed to future study.Through analysis and research on safety theory and its application, the semi-submersible vessel safety theory get enrich and it improves the stability rules and unity. In the actual operations, the study also provide guidance for cargo transport operations.