A method for assessing the fatigue strength of hull structures after high-temperature fire exposure

Due to the unclear mechanisms of ship fire development and the insufficient understanding of the post-fire mechanical property evolution of marine steel, there are no systematic and reliable methods for assessing the fatigue strength of hull structures undergone fire. In this study, a holistic framework based on the integration of multiple techniques is proposed for the fatigue assessment of hull structures after high-temperature fire exposure. First, a steady-state tensile tests are conducted on AH32 marine steel under high-temperature and post-fire conditions to obtain the static mechanical parameters. Subsequently, fatigue tests are carried out on typical hull welded joints to establish their S-N curves after high-temperature fire exposure. Then, a two-zone large eddy simulation technique is integrated with the finite element method to reconstruct the residual state of the hull cabin structure after fire. Finally, spectral analysis is employed to evaluate the fatigue strength of hot spots in the hull structure after high-temperature fire exposure. The results indicate that the degradation of steel fatigue performance caused by high-temperature fire and the structural deformation induced by thermal stress significantly reduce the fatigue life of hull structures after fire.