Structural Analysis of a Subsurface Cage for Sea Cucumber, Stichopus japonicus, Grow-out Using Numerical Modeling Techniques

AbstractThe structural characteristics of a subsurface cage system for sea cucumber, Stichopus japonicus, grow-out were analyzed by using numerical modeling techniques. The cage system was constructed of polypropylene pipe and netting and weighted to sit on the seafloor bottom. Inside the cage, concrete blocks were used for animal aestivation and weight and a thin-plated device was mounted for animal movement. Environmental loads on the structure, resulting from a prescribed irregular wave field with and without currents, were first determined with a Morison equation-type finite element model. The structural response of beam and truss cage components was then calculated with the software MSC.MARC/Mentat. In addition to the irregular wave and current input forcing parameters of the structure, response was also calculated for possible forces incurred during lifting operations. Reaction loads, bending moments, axial tensions, and von Mises stresses of the sea cucumber cage structure were calculated for evaluation. The results of the study indicate that the combination of numerical model analyses presented can be used to assess structural integrity of these subsurface cage systems. These techniques will become more important as the industry expands and economics of scale promotes the construction of larger sea cucumber containment structures.