A Norwegian Standard NS 9415 (NAS, 2003) has been introduced to the offshore fish farming industry in Norway. This is the first standard dealing with offshore fish farm facilities. The main objective of the standard is to reduce environmental pollution by fish escape. The work process leading to NS 9415 revealed the need for research work in several areas to enhance design criteria with the objective of having a consistent safety level through out the life cycle of a fish farm facility. This paper presents results from a government supported research project with the objective of enhancing criteria for design and operation of fish farm facilities. A case study of a fish farm facility representative for the majority of polyethylene based fish farms in Norway is presented and the sensitivity of such fish farms to variation in the mooring system is shown and discussed for design relevance. The sensitivity of net cage volume to current and weights is presented and discussed. Possible hazards from operational conditions are listed.
As of April 1st 2004 all new marine fish farms in Norway need to be certified to comply with technical criteria in a new Norwegian Standard, NS 9415 (NAS, 2003). This paper gives an overview of the design rules. Marine fish farms have a strongly flexible hydroelastic behavior. The design rules have revealed the need for calculations to verify the structural capacity of such facilities. This paper describes how loads and response are derived on the fish farm structures. In order to account for the large geometrical deflections occurring in fish farm components such as the net and anchor cables which interacts with stiffer structural components, time domain simulations analysis of such facilities is required to assess the structural integrity. This paper report a proposed practical calculation method and results from model tests have been carried out to validate calculations. Good correspondence was shown. Additionally some applications are described.
This paper presents how the design verification process for a tidal current power plant was carried out, and points out the challenges needed to be addressed in the technical assessment phase of the concept. The rules and regulations found suitable for the design process are presented. The paper focus mainly on what analysis is required to validate the capacity of the structure. The structure is exposed to a harsh offshore environment. The relative importance of the different loads and load effects is shown and discussed. The need for hydroelastic coupled analysis is demonstrated. The work shows that interactions between the main components are of large importance. There are interaction effects between moorings and structure as well as between turbine blades and structure. In fact the fully integrated system needed to be analysed as an integrated system, hence the need for coupled analysis. Although the structure was designed to derive energy from tidal currents, wave induced forces showed as important as currents for the structural integrity of the unit. The analysis demonstrated the versatility of the used FE analysis program AquaSim. This program is developed specifically to carry coupled analysis with hydroelastic interactions between structure and fluid. The FE program is in wide use within the Aquaculture industry. It is also in wide use in the offshore industry including moored systems and towed seismic equipment.
This paper presents how analysis can be used in the design and the design verification process for towed equipment. Analysis of a seismic gun array has been carried out and points out the challenges that need to be addressed in order to obtain an assessment of the system. It is shown how analysis should be carried out to obtain proper design verification. Applicable rules and design criteria are presented and discussed. The work shows the importance of carrying out a coupled hydroelastic analysis of towed equipment. The strong effect of waves and currents to positioning of equipment is shown.
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