Fatigue Design of Floating Fish Farms Based on Load and Response Interaction

摘要

A study of fatigue design for floating fish farms based on non-linear time integration of thernequation of motion is presented. The study is based on a structure used in Norwegian fishrnfarming today, i.e. a floater made of steel cylinders configured as a square.rnThe hydrodynamic loading is modeled taking dynamically updated water plane area, freernsurface location as well structural response into account.rnHydrodynamic loading is implemented as a combination of Morison loading and buoyancy.rnMorison loading is found using relative velocity and acceleration and considering the level ofrnsubmergence. Buoyancy is implemented as non-linear springs taking into account thernaforementioned non-linear effects.rnA fatigue design procedure for floating fish farms in steel is suggested. The procedure is basedrnon a time domain analysis of the structure in irregular waves. For each sea state a one-hour (realrntime) analysis is performed and the stress history for an assumed critical location is collected.rnBased on the stress histories, the damage is found based on rain flow counting and SN-curves.rnIt is shown that it is realistic and feasible to base a fatigue design procedure on time simulationrnof all sea states using a conventional PC.