Finite element model of USCGC STRATTON overlaying the actual ship

measurement location was derived using a combination of hydrodynamic and structural finite element tools.

The wave information needed for the red line was derived from the Copernicus wave satellite database. A single significant wave height, period and heading was used to describe the sea state. Although only one deployment is shown in the figure, multiple deployments were investigated. From this analysis it was found that the total cumulative, calculated damage is two to four times higher than the measured damage for the various deployments. In Copernicus, however, multiple wave systems can be distinguished. This subdivision provides a more accurate description of the sea state. And, as can be seen from the figure, this also leads to a more accurate assessment of the accumulated fatigue damage.

Cost-effective solution There are various assumptions that influence the performance of a VHSM system. The presence of multi-modal sea states has

report 17

been mentioned. Other features include the spectral wave shape and wave spreading, but also non-linear response characteristics such as whipping. Further analysis of combined traditional and virtual hull monitoring will provide knowledge on the accuracy and shortcomings and will also provide insight into potential correction factors for these shortcomings.

A combination of traditional monitoring and VHSM provides a cost-effective solution to fleet monitoring. The thorough understanding of the accuracy of design tools and methods obtained from a limited number of ships can be applied in the analysis of similar vessels. From the initial work done so far it seems virtual hull monitoring certainly deserves its own role within MARIN’s portfolio of monitoring services.

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