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Article type: Cover
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Published: March 30, 1987
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Article type: Index
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Published: March 30, 1987
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Article type: Appendix
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Published: March 30, 1987
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Mikio TAKAGI, Yasushi HIGO, Kazuya NAKAMURA
Article type: Article
Pages
1-10
Published: March 30, 1987
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There have been many studies concerning the stability problem of a semisubmersible platform since several tragic accidents of it had happened. Particularly it is important to stabilize the damage condition of semisubmersible platform in rough sea conditions from the safety viewpoint of a floating structure. So far, however, there have been very few study concerning it above mentioned. In this paper, an attempt to stabilize the damage condition of semisubmersible platform with a large list is made. A time domain simulation is developed to predict the motions of a semisubmersible platform in rough seas, in which the dynamic balance of the platform may vary with time due to the adjusting the ballast water in the lowerhull. Comparing with the experimental results of the platform with a large list in waves, it is made clear that the computer simulation fairly well estimate the dynamic behavior of the platform. In order to stabilize the platform with a large list, the adjusting the ballast water by using the pumping system is proposed. It is made clear from the time domain simulation that this method is very useful for stabilizing the damage condition of the platform with a large list in waves. Finally an unstable rolling oscillation of the platform with a large list angle is discussed.
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Tsugukiyo HIRAYAMA, Toshihito Ohno, Haruhira ARAKAWA
Article type: Article
Pages
11-20
Published: March 30, 1987
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In this paper, moored discus buoy characteristics (motions, accelerations, mooring tensions) in currents, regular waves, transient water waves, irregular waves and breaking waves are investigated in details, but winds are not included. For this study four types and 1/10, 1/20, 1/50 scale models are used, and a running mooring system is considered for generating relative current speed. Model motions are recorded by a remote measuring technique. From this study, following main points are concluded. (1) Frequency transfer functions in currents can be estimated farely well by the so called Strip Method even for such a full and flat body. (2) Effects of mooring rope on buoy motions are small like moored semi-submersible plat forms. (3) Capsizing rate and safety zone from capsizing in breaking waves could be shown, (4) Effects of type difference on infinitensimal motions are very small but on capsizing characteristics in breaking waves are farly large at large pre tensions or in small breaking wave height.
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Tsugukiyo HIRAYAMA
Article type: Article
Pages
21-27
Published: March 30, 1987
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Adding to the estimating system for one dimensional spectrum, estimating system for directional wave spectrum on board is developed measuring the time history of motions or acceleration of a running ship. Calculation of directional wave spectrum is made by adopting the so called Maximum Likelihood Method and by using a micro computer on board. There is a difficulty in transforming encounter frequency to absolute frequency, but here, we introduced a practical settlement for this problem.
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Yasuyuki TODA, Yoshikazu KASAHARA, Ichiro TANAKA
Article type: Article
Pages
29-38
Published: March 30, 1987
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The interaction between a propeller and a flow field around a full form ship is investigated. A method is presented for the prediction of effective velocity field from measured nominal velocity field, The prediction is made two-dimensionally, with three dimensional correction, by use of modified Huang et al.'s method under the assumption that the effect of vorticity, whose axis is vertical, is dominant for the distortion of velocity distribution due to propeller suction. The agreement between measured and predicted total velocity distribution with propeller is comparatively good. Characteristics of effective velocity field around a full form ship is discussed.
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Ryotaro OGIWARA, Yoshiteru SAKAI, Mikihiko NAKAYAMA, Noriyuki KAMOI, K ...
Article type: Article
Pages
39-50
Published: March 30, 1987
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This is the report on the strength analyses of Type B semi-membrane tank based on the requirements of the IMCO (the present IMO) Gas Carrier Code (the present IGC Code). The IMCO Code became effective in 1980, and then, it became compulsory for Type B semi-membrane tank with partial secondary barrier to prove its reliability using model tests, refined analytical tools and analysis methods to determine stress levels, fatigue life and crack propagation characteristics. The authors, therefore, made the following extensive strength analyses with regard to a semi-membrane type tank of a 77,400m^3 LPG carrier, including various studies and tests concerned. (1) Development of an FEM program for contact problems involving a thin-plate structure like a semi-membrane tank (2) Stress analysis by the FEM program for contact problems (3) Fatigue strength analysis (4) Brittle fracture strength analysis (5) Study on partial secondary barrier (6) Tests to obtain necessary data for these analyses (fatigue test, crack propagation test, brittle fracture test, leak test etc.) It was proved through these analyses that this tank satisfies all the requirements of the IMCO Code for Type B Tank. This tank was approved by Nippon Kaiji Kyokai and the U.S. Coast Guard as Type B Tank. Based on the results of this study, we built, first in the world, an LPG carrier with Type B semi-membrane tanks, M.S. "Clean River", under the supervision of NK.
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Isao NEKI, Hideaki TATAMI
Article type: Article
Pages
51-59
Published: March 30, 1987
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The boundary element method (BEM) has the merit to reduce the data of calculation model in the numerical analysis and the expectation to obtain the accurate results because of using the theoretical fundamental solution. Many papers and reports about BEM were published on the various fields, and there are many applications on the structural analysis. But, BEM for the structural analysis of cylindrical shells is very few, in spite of its importance. In this paper, the authors developed the new analysis method of BEM for cylindrical shells, and investigated its accuracy.
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[in Japanese]
Article type: Article
Pages
61-71
Published: March 30, 1987
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Article type: Appendix
Pages
73-
Published: March 30, 1987
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Article type: Appendix
Pages
75-82
Published: March 30, 1987
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Article type: Appendix
Pages
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Published: March 30, 1987
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Article type: Appendix
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Published: March 30, 1987
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Article type: Appendix
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Published: March 30, 1987
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Article type: Appendix
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Published: March 30, 1987
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Article type: Cover
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Published: March 30, 1987
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Article type: Cover
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Published: March 30, 1987
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