Research On Design And Strength Of Spread Mooring And Riser Interface Structure For General Purpose FPSO

With the ever-changing international situation and the rapid development of the domestic economy,the demand for oil as a strategic resource is getting higher and higher.General purpose FPSO refers to a new design concept ship type that is applicable to a variety of sea environmental conditions,a variety of mooring methods,a variety of topsides,compatible with a variety of riser systems,and can be configured with a detachable propulsion system to meet the combination of various design parameters.General purpose FPSO also has the unique advantages of rapid response to oil and gas field development,batch construction,short construction cycle,flexible deployment mode and low towing cost.Mooring modules and riser modules have the characteristics of diversity and uncertainty,which bring new problems to the design of spread mooring interface structures and reinforcement structures,as well as riser interface structures and reinforcement structures.This thesis mainly designs and researches the spread mooring interface structure and reinforcement structure of the target general-purpose FPSO,as well as the riser interface structure and strengthening structure.Combined with the main hull model,the structural strength check analysis and optimization research are carried out,and a set of suitable general-purpose FPSOs is formed.The main contents of this thesis are as follows:(1)Study the spread mooring and riser interfaces and reinforced structural types mainly used in the active FPSO,and compare and analyze the advantages and disadvantages of different structural types.Combined with the general arrangement drawing and basic structural drawing of the target general-purpose FPSO,the layout principle of the spread mooring at the bow and stern and the interface structure of the midship riser pipe is mainly to meet the strength requirements.The spread mooring at the bow and stern and the interface structure of the midship riser are preliminarily designed.(2)The finite element model for spread mooring interface and strength check analysis of reinforced structures at bow and stern is established,and the material parameters of the calculation model and the criteria for strength analysis are determined according to the requirements of relevant ABS specifications.The main conclusions are as follows: The dominant condition that affects the structural strength of the spread mooring interface at the bow and stern is the condition in which the tension of one mooring chain reaches the minimum breaking load and the other mooring chains are in a state of pretension.The chain guide support structure and the reinforced platform plate connected to it are the main load-bearing components,and safety must be paid special attention to.(3)The finite element model of the riser interface and the strength check analysis of the strengthened structure are established,and the boundary conditions and load conditions are determined with reference to the relevant content of the ABS FPI specification.The main conclusions are as follows: The dominant working condition affecting the structural strength of the upper riser platform at the riser interface is the working condition under the design load condition of the ultimate working condition,and the leading working condition affecting the lower riser support structure is the working condition under the design load condition of the temporary working condition.(4)In order to ensure that the strength of the spread mooring and riser interface structure meets the requirements of the classification society,the optimal design of the bow and stern spread mooring interface,the reinforcement structure,the midship riser interface,and the components of the reinforcement structure that do not meet the strength requirements is carried out.Through the design and finite element model calculation of spread mooring and riser interface and reinforced structure of general-purpose FPSO,a set of optimization scheme for spread mooring and riser interface structure design suitable for target general-purpose FPSO is formed,which can provide reference for shipyards in designing spread mooring and riser interface structure of FPSO.