Development of structural modeling techniques for evaluating HDPE plastic net pens used in marine aquaculture

Finite-element modeling (FEM) techniques are developed to determine the structural capabilities of net pen flotation structures made of high-density polyethylene (HDPE). The modeling approach uses shell elements and localized failure criteria to predict critical loading conditions. Finite element modeling simulations were performed using values for the modulus of elasticity for weathered HDPE determined from a series of tensile tests. Poisson's ratio and yield stress used with the approach were obtained from standard manufacturers values. To investigate the method, a series of experiments were performed in the laboratory by testing circular sections of HDPE pipe to localized failure ("kinking"). The same test was replicated with the FEM using localized failure techniques. Laboratory and model results were within 16%. A FEM was then built to represent the complex geometry of a net pen flotation structure deployed at an operational fish farm located in Eastport, ME, USA. Simulations were performed using attachment line tension values measured at the site. The goal was to assess flotation pipe stress levels for typical operational conditions. Simulations were also performed to investigate the maximum capabilities of the net pen structure with different attachment line configurations. Quantifying the operational limits will become more important as these systems are considered for more exposed, energetic environments. (c) 2007 Elsevier Ltd. All rights reserved.