Mooring with Multicomponent Cable Systems

Relative to the present-day need for offshore operations involving the use of moored vessels, mooring system design has become quite complex. Since a proper choice of mooring line components in the form of anchors, clump weights, chains and cables is vital for vessel station-keeping and mooring system survival, the adequacy of the mooring system under consideration must be checked out by suitable analysis techniques. This paper gives a general discussion of the various mooring line components available for use, presents an analysis tool to determine the stiffness characteristics of a multicomponent cable including the effect of line stretch, and demonstrates how these could be included in the dynamic analysis of an offshore construction vessel moored by a multileg anchoring system. The maximum limiting tension of the mooring line considered, which is a combination of anchors, clump weights, chains and cables is determined from the several breaking strengths and anchor capacities associated with the various cable configurations that can occur. Finally, in order to illustrate a practical application, the dynamic response of a moored production barge subjected to external environmental forces is examined.