Numerical simulation of nonlinearity and viscoelasticity of synthetic fibre rope for taut moorings in deep water

Synthetic fibre ropes are preferable for taut moorings due to their low weight to strength ratio, which facilitates the reduction in cost. But the fibre ropes exhibit significant nonlinearity and viscoelasticity behaviour, which introduces difficulty in predicting the mooring dynamic response. The present study proposes a lumped mass method to simulate the dynamic response of mooring line. The elastic modulus of the fibre ropes is assumed to increase linearly with the instantaneous tension and a dashpot parallel to the spring is employed to represent the viscoelasticity. Six mooring configurations are employed and different types of motion are imposed to the fairlead. The energy dissipated by the hydrodynamic force and the viscoelastic force is calculated by the work done, which clarifies the damping characteristics of taut mooring lines.