Static and fatigue analysis of multi-leg mooring system

The report describes theoretical developments for evaluating the fatigue life of multi-leg mooring systems. It is a continuation of previous, detailed research on the statics and dynamics of mooring line. The basic conclusion from the previous phase of this study on mooring dynamics was that cables are subject to substantial tension amplification in deeper waters, because they are forced by the action of drag to employ the large elastic stiffness, instead of the small catenary stiffness, in response to oscillatory excitation in the wave frequency range. The basic conclusion from the present, second phase of the effort is that multi-leg lines have a relatively small fatigue life in deeper waters, due to the basic amplification mechanism discovered during the first phase. This finding makes the use of the computational methods developed by the authors very useful, because they allow a realistic estimate of the fatigue life at a reasonable small cost.