The ideal foundation for your next project
In order to fully capture the potential in marine engineering and computerization offered by the latest technology, DNV GL has developed new rules for hull structures. These rules are an improved foundation for ship designers to construct vessels that are optimized to meet the needs of their customers. They also provide an enhanced framework for designing innovative solutions for the maritime industry.
Combining accuracy with efficiency
The introduction of Equivalent Design Waves (EDW) marks a significant change in the way dynamic loads are calculated in the DNV GL rules. The new advanced load concept is a major step towards a more realistic representation of the environmental loads.
Along with our state-of-the-art capacity models, this concept will increase the consistency in the safety level applied for the complete hull structure. In addition, this approach will also accommodate challenges related to the development of novel and unusual designs.
The EDW approach will provide for a more accurate representation of the dynamic loads and consequently enable a more precise stress distribution for the ship structure. Combined with the latest structural capacity models and clearly defined acceptance criteria, it will give designers and shipyards an improved framework to address critical areas. As such, it will also provide for a better basis to optimize the structure. To verify that the new methodology is in line with operational experience, we have performed extensive consequence assessments of existing designs.
The state of the art - simplified
Presently, the most advanced and accurate load response analysis that can be performed is full spectral analysis (FSA). This method investigates the responses on a structure exposed to a full range of multidirectional waves for specified sea spectra. But the time-consuming and costly nature of this method makes it unsuitable as a general approach for ship design.
An equivalent design wave (EDW) is a wave for which a selected structural response is equal to a target value for an extreme response from the FSA. An EDW aims to recreate a similar dynamic response for a specific target area.
The EDW approach significantly reduces the number of required structural response calculations needed to obtain a good representation of the environmental loads. And we have made a substantial effort in research and comparison studies to ensure that the EDW approach provides similar results to those of the FSA.
Compared with a full spectral analysis, the major benefit of the EDW approach is that it significantly reduces the computational time and costs while providing the same realistic results. It also allows us to derive simplified formulas for hydrodynamic loading and associated load combination factors.
In short, the new rules will accommodate designers to apply the steel where it is really needed. This will result in ships more suited for their purpose, requiring less maintenance and repair during their lifespan.
To account for the more advanced load descriptions, our calculation tools have been significantly updated, providing even better support for an efficient design process.
In addition, an extensive effort was made to ensure that the calculation scope is in line with the respective ship type. Flexibility is provided by allowing both simplified conservative requirements and advanced direct analysis. Combined, the new rules and tools will give a much improved basis for developing designs that are fit for their purpose.
The application of EDW in the new DNV GL rules represents an important shift towards a more consistent and accurate load description. Through a substantial effort in research and comparison studies, DNV GL has made the approach suitable for the complete range of ship types, shapes and sizes.