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Item type:Publication, Access status: without files , Local stress analysis of welded ship structural details under consideration of the real weld profileThe fatigue strength of welded ship structural details can be assessed by local stress approaches. In contrast to the widely applied nominal and structural hot-spot stress approaches, the notch stress approach can explicitly consider the shape of the weld. Usually a quite simplified weld profile is assumed, but it is also possible to reproduce the real weld profile, if data is available. In the paper, the notch stress approach is described and techniques are introduced for measuring the weld profile, focusing especially on the laser-based sheet-oflight measurement system. Taking different bracket connections as an example, which have been analyzed in a recent research project, the derivation of a realistic weld profile from the laser measurement is described, introducing a fictitious notch radius to account for micro-support effects of the material. The so-called effective notch stress is then analyzed using finiteelement submodels of the coarse bracket models. The fatigue test results are compared with design S-N curves based on the computed effective notch stresses as well as with the structural hot-spot stresses derived from the coarse models. Finally, conclusions are drawn with regard to the practical application in ship structural design.Publicationtype: Conference Paper30 - Some of the metrics are blocked by yourconsent settings
Item type:Publication, Access status: without files , Dynamic stability criteria based on the simulation of full scale accidentsIt has become obvious that modern ships suffer from problems related to their seakeeping-behavior, which is mainly related to large amplitude roll motion in head and following seas. As these effects are not covered by the existing intact stability criteria, an additional concept was developed. This new concept allows us to quantify the risk of the occurrence of large roll angles by calculating a capsizing index. The question left open so far was, how much stability would be required for a certain ship to meet a distinct safety level against capsizing. This paper presents an approach addressing this question based on the analysis of some real capsizing accidents analyzed by applying various criteria proposed in the past, in comparison to the new intact stability index. For this purpose our simulation code, ROLLS, was applied, taking into account relevant effects such as cargo shift, additional heeling moments and water ingress.Publicationtype: Conference Paper5 - Some of the metrics are blocked by yourconsent settings
Item type:Publication, Access status: without files , The propulsion and maneuvering concept of the BCF- super C- Class double end ferriesOne important milestone of British Columbia Ferries (BC Ferries) during their Major Fleet Replacement Program was the development of a new Double Ended Ferry class to replace their existing C-Class vessels. The final design of the ships called the BCF Super Class Ferries, which are actually the world's largest double end ferries, was finally carried out by Flensburger Schiffbau- Gesellschaft (FSG), Germany. Some of the Design requirements put forward by BCF had been very hard to fulfill in the final concept. Most challenging was the demand for extremely low fuel consumption, low wake wash, and very good steering performance that had to be combined with the requirement for a diesel electric power plant. Furthermore, the operational profile of the vessel required a very short acceleration time of the vessel from zero up to full design speed, which is quite high with 21 knots. These requirements lead to an unconventional propulsion concept with bow and stern CPP- Propellers which are operated in constant rpm mode where the bow propeller feathers with the trailing edge. This propulsion concept is embedded into a completely new hull form that was developed on the basis of numerical flow simulations. The concept was finally derived from the numerical and experimental evaluation of many alternative concepts. With respect to the maneuvering demands, most challenging was the fulfillment of the Active Pass Route operation, which was demonstrated by a full mission maneuvering simulation carried out during the initial design phase. The harbor approach procedure requires a mode shift which includes the de-feathering of the bow propeller at full speed and the starting procedure of the bow drive motor into the constant shaft speed mode using a soft starter. To do so, the automation system of the propulsion plant was combined with the maneuvering model that allowed for the determining of all important interactions of the complex systems; thus finally leading to the design of the propulsion control system. The paper shows that the technological challenges of such a complex kind of ship can only be tackled in close cooperation between the owner, the shipyard, the main suppliers, and the research institutions, as many design tasks require scientific simulations on a high level.Publicationtype: Conference Paper61 - Some of the metrics are blocked by yourconsent settings
Item type:Publication, Access status: without files , Development of a probabilistic methodology for damage stability regarding bottom damagesToday damage stability calculations are carried out in three major steps: Firstly a damage generation, secondly a system response and thirdly a validation of the system response are carried out and therefore the generation of damages is highly time consuming. This paper suggests a methodology to automate the damage generation by using Monte Carlo simulations. This methodology is exemplified with bottom damages and based on the probability density functions given in the IMO/ MARPOL- Oil-outflow regulations. The paper shows on one hand the statistical inconsistency of these functions, but will on the other hand demonstrate that damage generation with the Monte Carlo simulations is applicable with very short calculation times. That opens the opportunity to compare different subdivision arrangements even in an early design stage of a vessel quickly. Furthermore this methodology can be extended to side damages, because the automization of the damage generating is in focus.Publicationtype: Conference Paper7