To understand the evolution of dynamic stiffness of damaged synthetic fiber mooring ropes, experimental investigations of polyester and high modulus polyethylene (HMPE) ropes are systematically performed utilizing a specially designed experimental system. An experimental procedure is proposed and test results show that the dynamic stiffness increases with increasing mean load and loading cycles, while decreases with increasing strain amplitude and damage level. The similarity criterion of dynamic stiffness is derived from the dimensional analysis for damaged ropes and verified by experiments. An empirical expression that accounts for the damage, mean load, strain amplitude, and loading cycles is proposed to describe the damage effect upon dynamic stiffness of synthetic fiber mooring ropes.

The present work proposes a novel structural configuration for floating wind farms after an investigation into the structural configurations of current floating wind farms. The uniqueness of the structural configuration lies in the ability to adjust its heading to wind inflow directions, i.e., the self-adaptive property. To verify the existence of the self-adaptive property, a structural design is performed, and a quasi-static framework to analyze the responses is established. To simplify the loads on wind turbines under yawed inflow conditions, empirical expressions for wind loads are proposed, based on which the quasi-static analysis is performed under the yawed inflow direction of 90 deg from the structural heading. The analytical result indicates that under yawed inflow conditions, the structural heading will eventually turn to align with the wind inflow direction on account of the structural configuration and the wind turbine control. Then, the effects of inflow wind velocity, initial offset, number of wind turbines, complex environmental conditions, and hydroelastic properties on the responses of the structure are investigated.

To obtain an optimum connection parameter combination for modular floating structures of multiple functions, an integrated methodology for the assessment and optimization is proposed in the present work, out of consideration for the balance between the functional performance and economic effect. To illustrate the whole process, two types of modular floating structures, i.e., a modular wave energy converter (WEC) and a modular mobile offshore base (MOB), are taken as the cases. For the two cases, connection configurations are first specified based on structural functions as well as environment conditions; then, quantified measurements are established and studied, based on which the following process of selection of optimization algorithms is done and the optimum solutions are obtained, making up a whole process of specification of the connection parameter combination for modular floating structures. The proposed methodology possesses the potential of offering guidance for the phase of preliminary design of connection structures of modular floating structures.