Design & Verification methodologies
Technical Bulletin 2013

Much effort has been expended on the development of accurate and robust deterministic tools designed to determine issues such as the hydrodynamic and structural behaviour of floating structures, fire propagation, fuel efficiency, noise emission. Highly technical tools, however, are worthless if they are not coupled with proper design methodology.

In the field of hydro-structure computation, the key point is the choice of design conditions representative of all the met-ocean states that the unit will encounter during its lifetime. The concept of Equivalent Design Wave (EDW) is used increasingly these days, but several types of EDWs exist, and the nature of the relevant wave type employed is very important. A comparison of several EDW types shows that the Irregular Design Wave is a much more robust concept than the usual Regular Design Wave, even if sometimes it is better to use a Design Sea State. In a second paper, a methodology is proposed to validate the choice of an efficient set of EDWs for several types of floating structures.

To validate alternative designs and arrangements in connection with safety of life at sea and for other specific scenarios such as onboard fire, it is important to have a quantitative method that allows a comparative approach. A severity index method, based on direct fire and evacuation simulations, has been developed by Bureau Veritas. This is a major improvement compared to current methods as it facilitates going beyond the time criterion, with a unique severity indicator, which is explicit regardless of the situation experienced. This indicator can be used directly in risk assessment and enables designs to be compared in a risk-based manner. Risk-based methodology is also applied to ensure the safety of new types of LNG floating units when no rules are able to frame fully the development of these projects.

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