Research on the ultimate strength of a bulk carrier considering elastic shakedown under cyclic bending moment

Objectives In order to evaluate the longitudinal ultimate strength of hull girder under cyclic bending moment accurately, the effects of elastic-perfectly plastic and Chaboche material model on the elastic shakedown and ultimate strength of hull girder under cyclic bending moment are studied. Methods Through the nonlinear finite element method, the ultimate strength numerical simulation of a double bottom bulk carrier considering the elastic shakedown under cyclic bending moment is carried out. In this study, the Bauschinger effect of the material during the reverse loading of the structure, the influence of the welding initial deformation and residual stress were considered. Results The calculation results show that the welding initial imperfections will significantly reduce the lower limit of elastic shakedown of bulk carrier, and the range of elastic shakedown of bulk carrier considering welding initial deformation and residual stress is the largest. After reaching the elastic shakedown under cyclic bending moment, the ultimate strength of bulk carrier considering the welding initial deformation and residual stress under hogging and sagging state is 7.15 % and 5.68 % higher than that under single loading, respectively. Conclusions The welding initial imperfections have a major impact on the elastic shakedown interval and the elastic shakedown ultimate strength of the bulk carrier, which should be carefully considered in the actual research and analysis.