Study On Load And Structural Response Characteristics Of Ship Structural Collapse

The accidents of ship collapse and fracture in waves occur from time to time,which not only causes ecological pollution to the marine environment,but also poses a great threat to the life safety of crew members.Therefore,the structural collapse of ship structure under waves has always been the focus and research focus of relevant researchers.Ship breaking and sinking accident is a dynamic process of loss of hull bearing capacity,and also is a nonlinear fluid structure coupling problem,which involves complex wave load nonlinearity,structural nonlinearity and their dynamic coupling problems.Therefore,it is necessary to explore a fluid structure coupling method considering wave load nonlinearity and structural nonlinearity to evaluate the structural collapse of ship structures under waves,so as to provide reference for ship structure design and safety evaluation.In this paper,the structural collapse of ships in waves is studied by means of joint model test and numerical simulation.Firstly,the model test of dynamic collapse of three compartment hull structure in wave making tank is carried out in this paper.According to the purpose and conditions of the test,and referring to the structure and loading characteristics of the container ship,a three-dimensional reinforced structure test model is designed and manufactured.The test model is composed of the head and tail rigid section and the middle test section.In the test,the head and tail section is used to obtain and transmit wave load,and the middle test section is used to produce collapse response.In the test,a series of working conditions with variable wave height and wavelength are carried out to test the wave pressure and structural dynamic response of the test model under different wave conditions.Then,a CFD-nonlinear finite element two-way fluid structure coupling method is proposed to simulate the collapse model test of ship structure.The numerical method combines the advantages of computational fluid dynamics(CFD)and nonlinear finite element(NFEM)in dealing with nonlinear problems,and can consider the nonlinearity of relevant loads and structures in the process of ship structure collapse.The CFD platform based on viscous flow theory adopts overset grid and volume of fluid method to accurately solve the ship motion and load;The dynamic collapse process of ship structure is simulated by implicit dynamic nonlinear finite element method.The twoway transmission of wave pressure and structural deformation information is carried out on the wet surface of the hull to realize the two-way coupling between CFD and NFEM.In order to consider the influence of inertial force of hull motion,the inertial force function is written and the mapping and transmission of inertial force is realized,so as to more comprehensively consider the influence of dynamic effect on structural collapse response.This method is used to simulate the ship structure collapse model test,and the numerical simulation results are compared with the test results to verify the effectiveness of the numerical simulation method.Finally,from the perspective of engineering application,the numerical simulation method verified by model test is used to evaluate the structural collapse response of4600 TEU container ship under wave.The structural collapse response under a series of variable wave height and variable wavelength conditions is calculated,the structural dynamic response of the hull under three states of elasticity、elastoplasticity and post ultimate strength is analyzed,the structural collapse mode of the container ship under waves is obtained,and the influence of variable wave height and variable wave length on the dynamic collapse response of the hull structure is discussed.