International Shipbuilding Progress - Volume 52, issue 2

Authors: Sung, Young Jae | Rhee, Key-Pyo

Article Type: Research Article

Abstract: A method is suggested to predict the stopping ability of the diesel ships with fixed pitch propeller. Based on sea trial measurements, the procedure of full astern stopping test is analyzed and modeled as the first order surge differential equation. Coasting with propeller windmilling state is taken into account for the reliable prediction of stopping ability. Duration of coasting state is determined from the propeller pitch ratio and the RPM at which braking-air is supplied. Resistance …and astern thrust are estimated from the speed and power at the maximum continuous rating condition. Calculated stopping distance and time are compared with sea trial measurements, and it can be confirmed that our method can be a useful tool to predict the stopping ability of diesel ships. Show more

Citation: International Shipbuilding Progress, vol. 52, no. 2, pp. 113-128, 2005

Authors: Koelman, Herbert J.

Article Type: Research Article

Abstract: The present SOLAS regulations on probabilistic damage stability have shown anomalies for irregular or complex compartment arrangements. In this paper it is motivated that the source of those problems can be found in the use of a limited set of crisp, sharp, damage boundaries, which arose from the analytical integration of the underlying Probability Density Functions. A possible remedy would be to postpone the integration process until an actual compartment or set of compartments is evaluated. …For practical reasons numerical integration is the most applicable method for that task. This proposal is elaborated and implemented in an experimental computer program, which is used to test the approach on a number of example cases. These tests have shown that there is a numerical deviation between conventional SOLAS and the proposed approach, which comes as no surprise. For practical reasons it is investigated whether new density functions, derived with the conventional method, in combination with numerical integration could lead to numerical compatibility. Finally, the effects of the current work on revision of the SOLAS rules are discussed, recommendations are made and subjects for further research are identified. Show more

Citation: International Shipbuilding Progress, vol. 52, no. 2, pp. 129-148, 2005

Authors: Senjanović, Ivo | Lju�tina, Ana Maria | Rudan, Smiljko

Article Type: Research Article

Abstract: A short introduction to liquefied gases and types of cargo tanks is given. Attention is paid to the independent tanks, especially those of C type operating under pressure up to 20 bar, for which pressure vessel criteria are relevant. Strength analysis for such a cylindrical tank with dished heads, design in accordance with the Classification Rules, is performed. The analytical and numerical approach, based on the theory of shells of revolution and the finite element method …respectively, are employed. The stress concentration in the cylindrical shell at the stiffening ring and in the sphere edge at its connection with the toroidal shell is analysed. In the former case the strength criteria are satisfied but in the latter they are not. The AD Merkblatt B3 tolerates such situation assuming that the FEM results are not realistic enough. Since the analytical solution indicates that the numerically determined stress level is overestimated only by 5%, the reinforcement of the tank head by a thicker spherical segment is recommended. The maximum stress is reduced to the allowable level. Show more

Keywords: cylindrical tank, dished head, stress concentration, shell theory, FEM, reinforcement

Citation: International Shipbuilding Progress, vol. 52, no. 2, pp. 149-167, 2005

Authors: Belenkiy, Leonid | Raskin, Yury | Tunik, Alfred

Article Type: Research Article

Abstract: Determination of limit loads based on the limit analysis is discussed in the paper for locally loaded grillages of ship structures, using ice loads and side grillages as examples. Both simple and complicated grillage arrangements with web frames and stringers are considered. The solution is derived using a combined version of the kinematic method allowing one to reduce the solution to successive examination of the limit loads for grillage members as isolated beams. Shear deformations are …accounted for in all cases. The results are presented as closed-form formulations. Show more

Keywords: plastic analysis, limit loads, local strength criteria

Citation: International Shipbuilding Progress, vol. 52, no. 2, pp. 169-182, 2005

Authors: Ni, S.Y. | Qiu, W. | Peng, H. | Hsiung, C.C.

Article Type: Research Article

Abstract: The panel-free method has been investigated for its validation in the first- and second-order wave force problems, where the geometry of a body surface is described by NURBS mathematically and the integration for the induced velocity and the potential have been performed using Gaussian quadrature. There are no assumptions on approximation for the body geometry and the source distribution, which have been always made in the conventional panel method. Accuracy and convergence of the panel-free method …have been demonstrated through the numerical examples for a moving submerged body and a Wigley hull. Show more

Citation: International Shipbuilding Progress, vol. 52, no. 2, pp. 183-196, 2005