Research On Boundary Condition Of DSA In The CSR

Common Structure Rules for ship was developed by the International Association of Classification Societies(IACS)based on the International Maritime Organization(IMO)Goal Based Standards(GBS).In the early stage,Common Structural Rules was divided into Common Structure Rules for Bulk Carriers(CSR_BC)and the Common Structural Rules for Double Hull Oil Tanker(CSR_OT).At present,the two relatively independent were unified and called Common Structure Rules for Bulk Carrier and Oil Tanker(CSR BC&OT),which was formally published on July 1,2015.Since the new standard published,the researches for it have increased,but the study on the boundary condition is seldom and remains to be further explored.This paper introduces hull girder loads adjustment principle and boundary condition of three holds direct strength analysis in the CSR BC&OT.A bulk carrier was taken as an example to establish the whole ship structure model,put pressures and adjust loads according to the requirements of CSR BC&OT,conduct direct strength analysis by support method and inertia release two boundary processing,then compare the same elements stress of the two boundary condition.The N5,N6 and N7 three holds model which cut from the whole ship model was to analyze by keeping the grids and loads unchanged,applying force and displacement boundary conditions according to the CSR BC&OT.Through the hull girder loads comparison in three holds areas and the elements Von Misses comparison in the mid cargo of the whole ship model and three holds model,the rationality on CSR BC&OT direct strength analysis boundary condition in three holds model of mid ship is verified.From the theoretical analysis,the simple support boundary condition for fore hold direct strength analysis in CSR BC&OT does not conform to the actual stress state and a new boundary condition similar to "overhanging beam" is put forward.The fore hold model which cut from the whole ship model was to analyze by keeping the grids and loads unchanged,applying force boundary conditions according to the three holds model direct strength analysis in CSR BC&OT,respectively using the standard simple support and the overhanging beam two kinds of boundary conditions.The element stress in the fore hold area of the whole ship model was taken as a benchmark to make subtraction in Von Misses of the same element in the mid cargo between the whole ship direct strength analysis and the fore hold direct strength analysis of two kinds of boundary condition.The subtraction results show that the stress in overhanging beam boundary condition is closer to that in the whole ship in the area of mid cargo on the premise of the same grids and the little different loads.Thus the overhanging beam boundary condition is more reasonable for the direct strength analysis of the fore hold.