International Shipbuilding Progress - Volume 49, issue 3

Authors: Žiha, Kalman | Pedi�ić, Marta

Article Type: Research Article

Abstract: This technical note suggests the use of constant, residual strength contours of a damaged hull girder section to enhance assessment of a ship's survival ability when exposed to longitudinal vertical bending after an accident. Following a general discussion on a ship's hull girder longitudinal load carrying capacity based on elasticity theory, on fully plastic resistance moment theory and on ultimate bending moment approach, the investigation focuses on the effects of different damage modes of a hull …section on the residual longitudinal strength of an impaired ship. The practical application of the computational link between the residual strength contours and a ship's survival is further clarified in given examples. Show more

Keywords: ship, ship construction, strength of ship, longitudinal strength, theory of plasticity, load-end shortening method, ship's survival ability, residual strength, ultimate strength, buckling strength, collision, tanker, bulk carrier

Citation: International Shipbuilding Progress, vol. 49, no. 3, pp. 161-176, 2002

Authors: Fang, Ming-Chung | Chen, Gung-Rong

Article Type: Research Article

Abstract: In this paper, the relative motion and wave elevations between two ships advancing in waves are studied by using a 3D pulsating source distribution method. The numerical technique with four series expansions and one integral representation submitted by Telste & Noblesse [14] is adopted for solving the corresponding Greens function and derivatives. Including the three-dimensional hydrodynamic interaction between two moving ships, a set of equations of twelve coupled motions were obtained and then extended to solve …the relative motions and wave elevations. The satisfactory agreement of the motion amplitude with experimental data for zero speed is obtained, which can be firstly used to support the validity of the present technique. From the present results, we can conclude that the 3D prediction technique developed here is indeed better than the 2D one concerning many physical respects. However, if the experiments for relative motion and wave elevation between two moving ships can be made in the future for comparison, the present method will be more rigorous. Show more

Keywords: relative motion, wave elevation, diffraction potential, radiation potential

Citation: International Shipbuilding Progress, vol. 49, no. 3, pp. 177-194, 2002

Authors: Molland, A.F. | Turnock, S.R.

Article Type: Research Article

Abstract: A description is given of an investigation into the flow straightening effects on a ship rudder of an upstream propeller and hull. In order to quantify these effects an experimental investigation was carried out using a 3.5 m × 2.5 m wind tunnel. The tests were carried out with an all-movable rudder and a representative propeller for drift angles up to ±15°. Three different lengths of centreboards were tested upstream of the rudder-propeller combination, together …with a representative hull. Flow straightening effects were found to be dependent on the type of upstream body, drift angle and propeller thrust loading. The effects of the three centreboards upstream of the propeller were found to be significantly greater than the effect of the propeller on its own. The straightening effects of the hull were found to be less than those for the centreline boards. There was an increase in flow straightening with increase in propeller thrust loading at a drift angle of 15° but at 7.5° drift this effect was less apparent and sometimes reversed. The overall results provide a better understanding of flow straightening effects and data for improving the prediction of manoeuvring rudder forces. The data for the centreline boards are likely to have applications for vessels with a relatively thin upstream skeg, whilst the data for the rudder plus propeller combination in isolation should be suitable for vessels with open water sterns, such as twin screw vessels. Show more

Citation: International Shipbuilding Progress, vol. 49, no. 3, pp. 195-214, 2002

Authors: Domnisoru, Leonard | Domnisoru, Daniela

Article Type: Research Article

Abstract: This technical note is focused on a local ship and offshore structure strength problem. The study consists in computing the stress field in the joints of framing elements, for two constructive solutions: round and broken line form bracket flanges, with or without supplementary stiffeners. Based on the obtained stress distributions, the effective bending breadth of the bracket flanges is calculated. The numerical computations are carried out using a 3D Finite Element Model. The numerical results point …out that high longitudinal and transversal stresses occur in the bracket flanges, so that the effective bending breadth of the flanges will be much reduced. Supplementary stiffeners disposed on brackets are diminishing the concentration zones. Diagrams were drawn up from the numerical results, concerning the effective bending breadth of bracket flanges as function of several geometrical parameters. Show more

Citation: International Shipbuilding Progress, vol. 49, no. 3, pp. 215-229, 2002