A fatigue analysis of the high-density polyethylene (HDPE) floating system of fish cage is presented. The fatigue analysis is based on the deterministic method and the finite element method combined with a hydrodynamic model. The stress of the floating collar is evaluated based on the joint use of the finite element method and hydrodynamic model. The fatigue life of the HDPE floating collar is about 20 years, which is using the deterministic method and evaluated by applying Palmgren-Miner cumulative damage theory and S-N curve of the material HDPE. Results indicate that the sensitivity of the fatigue life to the wave height is more important than that to the wave period.


Due to the growing domestic demand for seafood and the decline of fresh water resources available to the near-shore aquaculture, developing the marine cage net aquaculture in the open ocean is becoming a worldwide trend in the aquaculture industry. Unfortunately, the detrimental environment condition in the unprotected open ocean may lead to the collapse and fatigue failure of floating fish farms. Thus, ensuring the security and sustainability of marine cage becomes an important issue.

In the past decades, numerous studies were conducted to analyze the hydrodynamic characteristics of net cage system. Tsukrov et al. (2005) evaluated the performance of a tension leg fish cage and predicted the overall dynamics of the system in the open ocean environment, using a consistent finite element to model the net panels and nonlinear elastic components of mooring systems Fredriksson et al. (2003) analyzed the reactions of the net cages in waves by physical and numerical methods and compared the results with field observations. To investigate the dynamic properties of a flexible net sheet exposed to waves and currents, Lader and Fredheim (2006) conducted a series of experiments and developed a numerical model in which the super element concept was used to simulate the net sheet. Kristiansen and Faltinsen (2015) proposed a screen type force model for the viscous hydrodynamic load on nets, simulating the net by a system of trusses and investigated the mooring load on the net cage by experimental and numerical study. Shainee et al. (2014) examined the submergence characteristics of the single-point mooring (SPM) cage concept in random waves with following current using numerical simulations and experimental model tests. Decew et al. (2013) used an acoustic method to monitor the deformation of a small-scale fish cage deployed in currents. Zhao et al. (2014) and Bai et al. (2015) analyzed the deformations of the floating collar in waves using the curved beam method.

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