Wave Induced Faroes and Motions of Tubular Structures 



as 



ix XX i xy'i 



F. = k X. + k 



(23) 



X- r K y- . 

 yx X yy'i 



These forces may then be transformed back to the oxyz coordinates 

 for inclusion in the equations of motion. The anchor spring constants, 

 k ... k are computed from a knowledge of the aforementioned 

 elasticity and weight-shape characteristics of the anchor line. 



In a tension leg mooring, the mooring lines are vertical and 

 provide essentially total restraint against vertical movement of their 

 upper ends. Figure 2 illustrates the horizontal force which results 

 when the upper end of such a mooring line is displaced horizontally 

 as a result of surge, sway, and yaw. The restoring force in the 

 direction opposite the displacement, x^, of the end of mooring line 

 n is given by 



F = -^x 



(24) 



The displacement, x , may be expressed in terms of its components 

 in the x- and z-directions , in which case the corresponding com- 

 ponents of Fp in these directions will be given by (24), 



-HORIZONTAL CX)MPONENT 



MOORING LEG "n" 



Fig, 2, Restoring force in tension mooring legs 



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