Analytical method to assess double-hull ship structures subjected to bulbous bow collision

The paper presents simplified analytical methods to assess the plastic deformation and failure of double-hull ship structures subjected to bulbous bow collision. To validate the methods, numerical simulations are conducted on double-hull tanker side structures including three frame spacings along the longitudinal direction and two stringer spacings along the vertical direction. The paper estimates the extent of damage within double hull ship structures during minor ship-to-ship collision, where the inner hull does not participate in dissipating incident energy. In the analytical methods, the nose shape of striking bulbous bow is simplified as a hemisphere or a cylinder with hemispherical ends. This equivalence is validated against the similar numerical force displacement responses using the actual bulbous bow and the simplified strikers. The analytical methods derive expressions to estimate the relation between the plastic deformation and the crushing force of the double-hull structures. The onset of fracture in the outer hull is evaluated by a simple formula based on experimental and theoretical analyses. Finally, the probabilistic structural absorbed energy until the rupture of specific struck ship with respect to the displacement of striking ship is assessed according to the statistical data of ship dimensions and the design principles of bulbous bow.