MOORING CABLE DYNAMICS 



by R. L. Webster 

 10 January 1980 



The dynamic responses of the mooring lines themselves become an important 

 consideration in deep water moors. It is the purpose of this note to outline 

 some of the characteristics of mooring lines, to describe an approach to 

 modeling them, and to focus on some of the problems encountered. 



Important Characteristics of Mooring Lines 



Special behavior features which may appear in significant combinations in 

 long mooring lines are: 



Geometric Nonlinearity - This is a large displacement effect which 

 produces a stiffness dependent on the deflections and preloads in the 

 line. As an example, consider a simple straight line segment with 

 negligible bending stiffness. The stiffness of the segment along its 

 axis is 



^axial = f + I (1) 



where A = cross-section area 



E = Young's modulus 

 L = segment length 

 P = preload in the segment 



Usually P is small compared to AE and is neglected; however, the stiffness 

 transverse to the line is not zero when P is not zero. It is 



P 

 '^lateral " L ^^^ 



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