Stern-cabin Strength Analysis Of Multi-function Rescue Ships

Multi-function rescue ships can do multiple salvage operations under bad weather conditions,which can provide guarantees for the rescue work of our country.The ship often has the long forecastle and there are different kinds of rescue equipment placing on the weather deck which took up large areas of stern.This arrangement type makes the local strength of stern more serious and that bring the difficulties in structural strength analysis.At present,there is no rule or guidelines for the structural design and strength check aiming at this ship type.In this thesis,on the basis of the features of layout and structure,a direct calculation method of strength based on a stern model is proposed,referring to the relevant specification of CCS.This calculation method includes the selection of cabin scope,boundary condition and load cases,calculation of loads,adjustment of shear force and bending moment,and the selection of allowable yield strength criterion.Finite element analysis and strength check are performed on a typical multi-function rescue ship by using the method proposed above.According to the Rules for Lifting Appliances of Ships and Offshore Installations,the strength of heavy-duty equipment and their support structures is calculated and checked.The results calculated by the local finite element method are used to compare with the results gotten by the stern-cabin finite element method which was proposed in this thesis and the result shows that the stern-cabin finite element method is reasonable and feasible.In this thesis,the stress concentration of long deckhouse ends is also analyzed and due to the assessment results,suggestions for the local structural design are put forward.The results show that such a problem can be alleviated through planting a circular-arc bracket on the end of longitudinal deckhouse casing.Besides,using the doubling plate to connect the deckhouse bulkhead with main deck can also reduce the degree of stress concentration and ensure the safety of hull structure.The research results in this thesis can be helpful and provide the reference for the stern-cabin strength assessment and the structural design of the superstructure ends of similar ship type.