International Shipbuilding Progress - Volume 55, issue 4

Authors: Senjanović, Ivo | Rudan, Smiljko | Ljuština, Ana Maria

Article Type: Research Article

Abstract: This work describes the remedy for a misalignment at the joint of two segments of hemispherical heads in a bilobe cargo tank. The misalignment is the result of a relatively thin spherical shell and production difficulties. Measurements of out-of-roundness show a rather large deviation of meridional camber and variation of radius in the head cross-section plane. At the ends of the segments the spherical form changes into a conical one. As a result a peak occurs in the meridional generatrix, which causes high stress concentration. The cross-section of the hemisphere at the segment joint is reinforced with a ring in …order to overtake the bending moment caused by the variation of circular radius. The ring dimensions are determined based on an approximate consideration. Stress concentration at the segment joint is reduced by two additional rings connected with a set of bars in the meridional direction. Angular distance between the bars is specified in such a way that the strength criteria, i.e. stress and fatigue requirements according to the Classification Rules, are satisfied. Stress distribution in the actual imperfect and reinforced structure is determined by the finite element method. Total static plus dynamic tank pressure is taken into account. Show more

Keywords: LPG carrier, bilobe tank, hemispherical head, misalignment, reinforcement, strength, fatigue, finite element method

DOI: 10.3233/ISP-2008-0049

Citation: International Shipbuilding Progress, vol. 55, no. 4, pp. 253-279, 2008

Authors: Shahid, M. | Das, P.K.

Article Type: Research Article

Abstract: The Finite Element Methods has become a common tool for engineering analysis and design subsequent to phenomenal increase in computing power available even on laptop and personnel computers. Further, design optimization and reliability analysis techniques and methodologies needing a number of evaluations of design problem at hand are becoming accessible and affordable. This paper concerns to review various techniques and methods that may be used in Reliability Analysis (RA) based on Finite Element Methods (FEM). A review of reliability analysis tools available within the ANSYS commercial FEA software as well as that of STRUREL, the commercial RA software is carried …out. A simple portal frame structure analysis has been done using various methods, and the results are compared for computational cost and accuracy. Show more

Keywords: Reliability analysis, structures, FEM

DOI: 10.3233/ISP-2008-0050

Citation: International Shipbuilding Progress, vol. 55, no. 4, pp. 281-300, 2008

Authors: Hu, Li-Fen | Ma, Kun

Article Type: Research Article

Abstract: This paper attempts to present a genetic algorithm-based counter-flooding decision support system for survivability evaluation and decision support in shipboard flooding accident. The developed system is also thought to useful as a crew training one, which is composed of a model base, a database and a man–machine interaction system structurally. The model base is of paramount importance to the system, which comprises three sub-models: a damaged floating position calculation model, a loading condition calculation model and a counter-flooding scheme optimization model. In order to solve the optimal strategy model, genetic algorithm, which is developed with roulette wheel selection, one-point crossover …and mutation, is used to choose the set of counter-flooding tanks should be filled or evacuated in order to achieve an optimal response to a flooding accident. The proposed evolutionary strategy enhances the diversity of population and the capability of search for the global optimum, which accelerates the evolution process of algorithm. The computational results validate the effectiveness of genetic algorithm. Show more

Keywords: Genetic algorithm, counter-flooding, decision support system, evolutionary strategy

DOI: 10.3233/ISP-2008-0051

Citation: International Shipbuilding Progress, vol. 55, no. 4, pp. 301-315, 2008

Article Type: Other

Citation: International Shipbuilding Progress, vol. 55, no. 4, pp. 317-319, 2008