Hydroelastic analysis and model tests on the structural responses and fatigue behaviours of an ultra-large ore carrier in waves

Abstract

To provide guidance on structural design for the life cycle safety of an ultra-large 500,000 deadweight tonnage ore carrier, the springing-induced high-frequency responses in waves, the resultant structural loads and their influences on the structural fatigue damage were investigated by employing the three-dimensional linear and second-order non-linear hydroelasticity theories of ships and the corresponding numerical methods. The theoretical predictions of the structural loads and responses and the comparisons with the model tests carried out in the towing tank of the China Ship Scientific Research Center are presented in this paper. The results for the hydroelastic responses of the ship at a forward speed and at zero forward speed in regular and irregular waves are illustrated, which provide the quantitative relations for the wave-motion-induced and the springing-induced structural loads, and their linear and non-linear components of the ship in different sea states, especially when the first flexible body resonant frequency is in the wave frequency region. The results show that the springing responses may occur in waves with any significant wave heights for such a large ship when the characteristic wave periods are less than a certain amount. The short-term and long-term distributions of the wave-induced and rigid-body-motion-induced structural loads and the springing-induced high-frequency loads are predicted. Based on the hydroelastic predictions of the structural loads, the accumulated fatigue theory is applied to assess the fatigue damage of the typical deck and bottom structural components of a ship serving in three shipping lines.