Deformation Analysis and Reliability Assessment of the Ship Hull in Irregular Waves

When the ship navigates in the sea, the dynamic deformation of the ship hull will be induced by the waves. The relative large deformation of the ship hull induced by the waves may affect the operation of some certain equipment. In order to keep the equipment operating normally, the influence of the ship deformation should be evaluated. The method for the calculation and analysis of the ship deformation is discussed here. The wave loads of the ship in unit regular wave amplitude are calculated based on 3-D linear potential flow theory. The sea pressure and inertial force of the ship are obtained and applied to the global finite element model of the ship. Under the quasi-static assumption, the structural deformation response in unit regular wave amplitude is calculated with the use of finite element analysis. Then, the amplitude frequency response of the relative deformation between two arbitrary positions in the hull is achieved. The history of the deformation can be obtained based on the simulation of deformation response in irregular waves or the modal superposition method. With the help of spectral analysis method, the spectrum of the relative deformation between two arbitrary positions in the hull may be obtained. The statistical analysis of ship hull deformation in the short-term sea state is realized. Considering the critical value of ship deformation, the reliability analysis method is adopted to assess the ability of hull to resist the deformation.