APPENDIX B 



MOORING ANALYSIS 



1. Purpose of the Program . 



Computer program BRKMOOR computes the forces and moments imparted 

 by a pair of mooring cables on a floating breakwater section. BRKMOOR 

 also computes the changes in the mooring cable tensions and the spring- 

 constant values for the moorings as the breakwater moves in sway, heave, 

 or roll . 



2. Program Description . 



Program BRKMOOR is written primarily in FORTRAN IV although FORTRAN 

 II print statements are used. 



The program consists of the main program BRKMOOR and the subrou- 

 tines LINE2, CHAIN, NYLON, EQULIB, SPRING, and LTERPS . 



BRKMOOR calculates the forces in a mooring cable by using a discre- 

 tized approximation to the cable. The cable is divided into the number 

 of segments specified in the input data. Each segment may be of a diff- 

 erent material or size. Each segment is in turn divided into a specified 

 number of sections. The cable is considered to be made of these sections 

 with the weight of each section concentrated at the node at the bottom 

 of the section. Connecting each node is a straight but elastic section. 



The main part of the program specifies IS different angles at the 

 attachment, ranging from nearly vertical to nearly straight to the 

 farthest reasonable anchor position. A first guess at a top tension is 

 made. 



LINE2 then sums down the cable computing forces and coordinates of 

 each node starting with the initial angle and initial tension. The po- 

 sition of the end of the cable is compared with the specified water depth 

 at the anchor. The initial tension is adjusted and the summation repeated 

 until the cable ends at the proper depth. Control then returns to the 

 main program. 



LINE 2 calls the subroutines NYLON or CHAIN to compute the strain of 

 the cable section of the appropriate material. If other materials are 

 used new subroutines should be written for strain computation, along 

 with the appropriate calling expression in LINE2. 



At each angle the cable forces at the attachment and the anchor 

 position are stored in arrays. EQULIB then computes the breakwater 

 equilibrium position for the specified conditions. 



SPRING is called by EQULIB. SPRING computes the change in mooring 



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