Study on Snap Tension in Mooring Lines of Deepwater Platform

Based on the theory of impact dynamics, the motion equations for a mooring line-floating body system after and before impact loading are established with consideration of the viscoelastic property of mooring lines. The factors that influence the taut-slack conditions of a mooring system are analyzed through classifying the taut-slack regions, which are defined by nondimensional ratios of displacement, frequency and damping of the system. The mooring lines of Jip spar platform is analyzed, and the snap tension characteristics of mooring lines are given, the factors that influence the maximum tension in mooring lines, including the mass of floating body, length of mooring lines, frequency and amplitude of external excitation, and pretension in mooring lines, are also analyzed through computing the dynamic response of system and parametric study. It is shown that the maximum tension increases with increase of the mass of floating body, external excitation and pretension and decreases with increase of the length of mooring lines, also, it is found that the influence of the nondimensional ratio of damping increases with increase of the pretension in mooring lines.