Abstract | A finite element method for the analysis of catenary mooring lines is described. In this a mooring line is modelled as a series of interconnected straight truss elements. These elements cannot withstand compression and resist external loads by changing their positions. A direct stiffness approach is used in the formulation to derive the equations of motion. The static solution presents special numerical difficulties: not only compound nonlinearities exist in the motion equations, lack of bending and compressional stiffness in the mooring lines also leads to occurrence of ill-conditioning of the tangent stiffness matrix. An adaptive dynamic relaxation technique is developed to overcome these difficulties and has proven very effective. The present finite element approach maximizes the flexibility in dealing with general mooring line configurations, arbitrary external loads and nonlinear boundary conditions. The formulations can be used for the final design and / or analysis of a general catenary mooring system and for model test design of such systems. |
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