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ObjectivesIn order to accurately assess the ultimate load-bearing capacity of a hull structure under cyclic loading, it is necessary to consider the effects of the cyclic properties of the load on the ultimate strength of hull stiffened plates. MethodsFinite element software ANSYS is used to carry out the numerical simulation of ultimate strength based on the elastic shakedown limit state under in-plane cyclic loading for 200 T-bar stiffened plates and flat-bar stiffened plates. The material Bauschinger effect, welding initial deformation and residual stresses of the hull stiffened plates under in-plane cyclic loading are considered in detail. Based on the stiffened plate nonlinear finite element numerical simulation results of the elastic shakedown limit state, the dimensionless ultimate strength of the stiffened plates is taken as the objective function, the flexibility coefficients of the plates and stiffeners are taken as the independent variables, and a formula for predicting the ultimate strength of hull stiffened plates under in-plane cyclic loading based on the elastic shakedown limit state is proposed. ResultsThe accuracy of the formula is verified through comparison with the nonlinear finite element simulation results. ConclusionsThis study has positive theoretical and engineering significance for the ultimate strength assessment of hull stiffened plates under cyclic loading.

ObjectivesTo fully consider intact initial imperfections, including welding initial deformation and residual stress, it is necessary to conduct a study on the plastic deformation distribution and ultimate strength of a box girder under different cyclic bending moments. MethodsFirst, an isotropic material model and the Chaboche material model are chosen. Using the Python language, programs are developed to directly apply the initial deformation in finite element software. Subsequently, ABAQUS software is employed to conduct nonlinear finite element numerical simulations of the ultimate strength of a box girder under different cyclic bending moment patterns. The analysis considers the influence of welding initial deformation, residual stress, material hardening and the Bauschinger effect. ResultsThe results show that under unidirectional cyclic bending moments, the bending stiffness and ultimate strength of the box girder decrease continuously as the number of cycles increases. The plastic deformation extends from the upper deck of the box girder to the side plate region. The plastic distribution region of the box girder with welding initial deformation and residual stress is wider in the ultimate state. Compared to a single loading and considering only the initial deformation, after three bidirectional cycles, the ultimate strength of the box girder decreases by 10.44% to 15.15%. Considering intact initial imperfections, the ultimate strength decreases by 8.41% to 14.50%. ConclusionsThe ultimate strength of a box girder considering intact initial imperfections under different cyclic bending moments decreases more moderately. The obtained results can serve as a reference for the study of the ultimate strength of box girders under different cyclic bending moments.

ObjectivesIn order to improve the accuracy of the ultimate strength evaluation of hull plates, this study carries out a nonlinear finite element numerical simulation of the ultimate strength of ship hull plates under cyclic loading based on the critical state of elastic shakedown. MethodsFinite element software ANSYS is used to primarily investigate the effects of elastic-perfectly plastic and cyclic-plastic Chaboche material models on the release of welding residual stress and ultimate strength of hull plates after reaching the critical state of elastic shakedown. ResultsThe results show that after the first cycle, the welding residual stress is basically released and tends to become stable after reaching the elastic shakedown state under cyclic loading, at which point the ultimate strength of the Chaboche model is greater than that of the elastic-perfectly plastic model. ConclusionsWhen performing the nonlinear finite element numerical simulation of the ultimate strength of ship hull plates under cyclic loading based on the critical state of elastic shakedown, it is necessary to select a material model that takes into account material hardening and the Bauschinger effect. The obtained results have a certain reference value for further research on the ultimate strength of hull structures under cyclic loading.

ObjectivesIn order to improve the accuracy of nonlinear numerical simulation of the ultimate load-bearing behavior of a hull stiffened plate, the effects of ideal elastoplastic, isotropic hardening and cyclic plastic Chaboche material models on the plastic yield distribution, compression and tensile ultimate strength of stiffened plates in their ultimate state are studied. MethodsFor a stiffened plate of the same size, ANSYS software is used to carried out non-linear finite element numerical simulation of ultimate bearing performance under axial cyclic compression and cyclic compression-tension loads. ResultsThe results show that different material properties have a significant impact on the ultimate bearing capacity of stiffened plates and the plastic yield distribution in the ultimate state. When carrying out nonlinear finite element numerical simulation of the ultimate bearing behavior of a hull stiffened plate, it is necessary to select the appropriate material model according to different load forms. ConclusionsThe results of this study can provide valuable references for further research on the ultimate strength characteristics and cumulative plastic failure mechanisms of hull structures under cyclic loading.