Nonlinear Dynamics of Multi-Segment Mooring Systems

Abstract

A general formulation applicable to multi-segment mooring systems is derived from first principles using the concept of lumped mass model and presented in this paper. The problem of seabed contact is addressed using an elastic-dissipative model of seabed. The contribution of seabed force along with the tension force is considered in creating global tangent stiffness matrix of the system. An implicit generalized-α method is used for time integration and it is modified for the current problem by developing an incremental iterative version of the method with corresponding predictor and corrector terms. An in house code named LM3D is developed based on the derived formulation. The code is verified with orcaflex results and also validated with experimental results. The main purpose of this paper is to showcase the reduction in tension observed in a simple branched mooring system when compared to a single line. Three configurations of branched system were considered and compared against a single line arrangement with same material properties. The dynamic analysis of this branched system was carried out with the developed in-house code.