A practical method for stability assessment of a damaged ship

Abstract Reliable onboard stability assessment for a damaged ship is of great importance to ship operators. This paper presents a practical method to calculate ship's damage stability directly from the full three-dimensional (3D) geometric models, in which the method of lost buoyancy is used. First, the computational database is established by cutting the 3D models of hull and compartments in transverse direction according to ship's frame distance table; Then, trapezoidal rule integration method is adopted to calculate ship's volumetric data; After that, the centre of gravity of liquid loads is calculated using Newton's iterative method; Finally, ship's equilibrium state of balanced trim and draft for a given heel angle is determined using a successive linear method, and the right level could be obtained. Lloyd's Register (LR) test cases for IACS UR L5 Type 1, 2 and 3 are used to verify the proposed method. In every stage of the test program, the method achieves a high-accuracy result, and thus can be used onboard to calculate intact stability and damage stability of ships by direct application of preprogrammed damage cases, especially for bulk carriers and tankers.