In the last two years a number of accidents with several dead or heavily injured crew members have been reported to the German Federal Bureau of Maritime Casualty Investigation caused by excessive roll motions with large transversal accelerations. All accidents happened on board of container vessels in situations of large stability and partial draft like in ballast or in laid-up situations. Also the accident situations were similar in all cases. During harsh weather conditions the crew tried to keep the ship against the incoming sea at constant slow speed. It was possible to reconstruct the accident events and the occurrence of high transversal acceleration values by numerical seakeeping simulations. To figure out if container vessels have an inherent danger of such problems a numerical study on a group of fifteen container vessels of different sizes was carried out in the mentioned accident situations. In this paper the reported accidents and the numerical investigation on the accidents are described, furthermore the results of the extended numerical study are presented and a phenomenological conclusion is drawn from the results.
A well-founded determination of steel structure scantlings is essential during the early design process of a ship or an ocean structure. In the first 4 up to 6 weeks of a new building project, the major part of the final building costs has to be fixed. Amongst others a proper steel weight estimation is crucial. The weight depends on the structural dimensions which are determined mostly by experience and rarely by direct calculations. Therefore, a simple direct strength calculation tool has been integrated in a ship design software. The tool uses structural and general ship design information. Besides the structural constraints, posed by the project design, the steel designer has to fulfill also the structural constraints posed by the classification societies. Normally they are checked with software solutions provided by the societies. However these software tools are not well adapted to the early design process as various design parameters change frequently. For this purpose a link has been created between a rule scantling tool on one side and a design software on the other. The link allows an automated exchange of steel scantlings and project information. By this the modeling and design work as well as the structure scantling and steel weight determination is performed in the design software tool, while the rule scantling tool is only used for a quick assessment of class conformity. With the help of the mentioned methods, the structure can be pre-dimensioned directly based on the early design model in accordance with the classification rules. Furthermore the steel dimensions can not only be optimized with regard to local and global loads, but also with regard to design boundary conditions. In consequence the early steel design process is improved by a more accurate steel scantlings determination and results in a better optimized steel structure as well as severely reduced time spent on the steel iterations.
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