The Research On The Stability Of Semi-Submersible Vessels With Transporting And Loading Awkward Cargo Under The Influence Of Wind And Waves

Semi-submersible vessel carrying awkward cargoes,which has high center of gravity and poor stability,is likely exposed to wind and waves.Hence,under this transport model,a minor mistake may cause serious losses of life and property.However,the requirements of meteorological conditions in the shipping industry are not consistent,so it is called the world's most dangerous shipping task.Based on a 50000DWT semi-submersible ship,this thesis focuses on the study of the stability issues of this ship type.It includes two aspects:stability conditions when ships undergoing the float-on operation and stability conditions while ships underway.The main study and conclusions are as follows:Firstly,this thesis introduces the theory of ship stability.According to the actual operation situation of the semi-submersible ship,it fully studies the whole process of the float-on operation and analyzes the change of the stability of the float-on operation.The key point of the research is when the main deck of ship is going to reach the waterline.Secondly,by means of the spectral analysis,the response amplitude operator is used to study the motion response under different meteorological conditions,so the frequency response function is obtained and the response amplitude of roll,pitch and heave is calculated.By studying the relevant regulations,this thesis derives the methods to calculate the inertia force,wind force and friction force in the float-on operation.Then,the model of stress analysis is established.Thirdly,for float-on operation,combined with particular example,this thesis assesses the ability of this vessel to resist wind and waves based on the requirements of the relevant regulations and considering the joint effect of wind and waves and stress analysis model.In this case,the wind is best not more than beaufort wind scale 4.According to the calculation results of the stress,the lasing lines are recommended to be used to reduce the lateral and vertical stress of the cargo.At the end,by means of numerical analysis,this thesis assesses the ability to resist wind and waves when the vessel is underway.The calculations show that the semi-submersible vessel can resist the wind 12 on beaufort scale.From the point of view of stability,the semi-submersible ship has better capability of resisting wind and waves.