Numerical modeling of nonlinear elastic components of mooring systems

This paper deals with the finite-element analysis of compliant structures containing nonlinear elastic components and subjected to loading by waves and currents. An efficient procedure to model such components is developed and implemented in a computer program. It can be applied to analyze nonlinear elastic ropes, rubber tethers, risers, and hoses. The elastic modulus is assumed to depend on the amount of strain in a component. The Newton-Raphson iteration scheme is modified to account for the change of elastic properties on each step of time integration procedure. The approach is applied to develop feed buoy mooring systems for the University of New Hampshire Open Ocean Aquaculture site. The complex nonlinear and viscoelastic load-elongation behavior of suitable high stretch mooring elements for this application is modeled to obtain realistic numerical predictions at sea conditions. Various designs and environmental loading scenarios are considered. Numerical simulations provide predictions of the overall dynamics of the system and maximum values of tensions in critical components.