Strength Analysis And Structural Optimization Of Truss-floating Tank Aquaculture Vessels

At present,there are two main types of deep-sea aquaculture facilities:closed aquaculture vessels and net-box aquaculture platforms.In order to make the aquaculture facilities both convenient for towing and fully adaptable to the aquaculture environment,this paper mentions a new type of truss-floating box type aquaculture vessel.As it is a new type of structure,no special design and construction specification has yet been developed,so the analysis of wave loads,wave sensitivity,structural stresses and strength checks for this type of vessel needs to be focused on.In this paper,the method of combining finite element software with parameter optimization software is adopted.Firstly,the stress calculation and strength check of the new truss-floating box type aquaculture vessel are carried out,and this was used as a basis for optimizing the structure of the vessel,thereby increasing its strength and reducing its overall weight.The main points are as follows:(1)The whole ship finite element direct calculation method based on the equivalent design wave method is used to calculate the stress and deformation results of the new truss-floating box type aquaculture vessel and check the structural strength: DNV SESAM software was used to build a whole ship hydrodynamic model and add load sections to calculate the wave load transfer function for this ship type in towing and operating conditions.The wave parameters for the worst conditions are determined from the maximum vertical bending moment and maximum wave torque,then structural stresses and deformations at this time are calculated to analyze the wave sensitivity and force characteristics of the type of vessel.Finally,buckling and yield strength checks are carried out on the basis of the normal and shear stresses of the plate and beam members under the worst conditions to verify whether the structural design of the ship has sufficient safety margins.And optimize the parts and components that do not meet the safety requirements.(2)Sensitivity analysis of parts and components that do not meet safety requirements: Linking iSIGHT with MSC Patran,Matlab,and using the DOE module’s parametric test method to vary the geometric parameters of the main components,sensitivity analysis was performed for maximum stress,maximum deformation and whole ship weight.Sensitive members,non-sensitive members and non-affecting members of the ship are screened out to provide reference for selecting design variables for structural optimization below.(3)Based on the optimization mathematical model,the optimization target are determined based on strength checks,the design variables are selected with reference to sensitivity analysis,and the multi-objective optimization of maximum stress,maximum deformation and total weight of the whole ship is carried out using the adaptive simulated annealing algorithm and multi-island genetic algorithm of the Optimization module.Based on the optimal solutions obtained by the two algorithms,the whole ship model is established to calculate the structural stress and the strength check is carried out again.The results show that the structural strength of the optimized midship truss structure has been significantly strengthened,and the total weight of the whole ship is also reduced;Both algorithms can fulfil the purpose of optimizing a ship,and as they have their own advantages and disadvantages,so it is necessary to choose the appropriate algorithm for optimization in actual use.