Numerical simulation of multi-material hybrid lines for offshore mooring

Abstract

In the last decades, great attention is being given to the development and improvement of station-keeping systems of offshore structures, such as wind turbines, energy converters, and platforms. In deep- and ultra-deepwaters installations, the use of synthetic, light-weight materials in lieu of chains and wire ropes is almost mandatory because of the deadweight of the entire mooring system. Several materials are useful for such purpose, such as polyester (PET), aramid, high modulus polyethylene (HMPE), and polyamide. However, since each material has its own advantages and disadvantages, an alternative is to design multi-material lines, with inserts of different materials aligned in series in one complete single line. In this sense, numerical tools are of utmost importance to the simulation of the behavior of the ropes in service conditions, and the quality of the results depend on the accurate definition of material properties. Here, we propose a constitutive framework for the finite element simulation of multi-material mooring ropes and test it to five configurations of multifilament samples combining PET and HMPE. We show that the model is capable of simulating the mechanical behavior of all configurations with a single set of constitutive parameters.