engleski

Design Principles and Criteria

Proactive, timely safety measures are of the foremost importance, not only in terms of safe voyages, but also because imprecise safety and environmental protection measures undertaken in the hope of decreasing the costs can actually result in phenomenal expenditure in the event of an accident. Consequently statutory and regulatory bodies and others concerned with the design of ships and offshore structures have in recent years worked towards integrating consideration of safety in the design process as exemplified by the concept of “ design for safety” . Among the most prominent relevant initiatives has been the adoption of “ Goal Based Standards” by IMO. In order to meet the challenge posed by the move towards goal-based standards several methodologies and technologies have been developed and/or refined. Central to this has been the application of risk-based methods, which explicitly account for both the frequency of a failure occurring and also its consequence. The application of first principles methods has increased in recent years, and has become even more necessary to provide input into risk analysis. Furthermore, application of risk contribution trees has facilitated the process of “ Design for safety” (as coined by the marine industry in the late 1990s). Another important development is the classification societies’ drive towards common rules. Current initiatives have focused on rules for tanker and bulk carrier structures. The common rules have been developed in the spirit of goal-based standards. Other important initiatives include the increasingly prominent role taken by ISO in developing the first truly international standards for the design of offshore structures. Market forces have driven designers to innovate. For example, the economics of the container trade necessitate faster and larger containerships, the growth of natural gas as a major energy source requires larger LNG carriers, and the search for new offshore oil fields has led to offshore facilities in deeper waters as well as the search for new ocean space utilization has led to Very Large Floating Structures and relevant technique developments. These forces have resulted in novel configurations, extended existing configurations, and increased the use of newer materials. Some progress has been made in adapting decision theory and using rational approaches to address these trends. The challenge remains implementing these tools in a design environment dominated by minima imposed by rulebased design. Criteria and principles regarding design and the uncertainties are main objectives for designers and relevant innovative techniques have been developed over recent years. The same forces that have driven designers to innovate have also been the impetus to take a more rational view of the inspection and maintenance process. This includes the development of asset integrity management schemes, the application of risk-based methods, 598 ISSC committee IV.1: Design Principles and Criteria the development of models for predicting structural degradation rates, etc. In the same vein hull monitoring systems are increasingly being seen as important sources of information to feed back into the design process. The design, construction and maintenance phases of a typical marine structure have in the past been isolated phases with limited interaction between each phase. The trends summarized above suggest a future in which a more integrated approach, or a more “ systems” view of the asset in question, will prevail. This development should be encouraged.

risk based approach;; marine structures; life - cycle design

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