The array described at the end of Section III has been taken here . 

 This array has a weight of 50 tons . Because it is hollow with rather thin walls, 

 approximately (600) (62) (2.25 tt) ^ 250,000 pounds of water are trapped in it 

 and have to move with it. Also, the apparent additional mass of the array in 

 water is about 250,000 pounds. Hence, the total dynamic mass of the array, 

 M^,, is about 600, 000 pounds. The value of A is equal to (600) (5) = 3,000 ft^ , 

 The value of 1.2 for a has been obtained from the literature. Therefore, 

 we have: 



P SL 



c wL _ 



U = —T. = TT" 0.353 



M M 



a a 



4apA|U I 



3 = ^ ^, ° = 0.16 lU I 

 3 IT M o' 



a 



^^ , An 



m = — = 1 . 47 UD 

 c 



Ie 1 = ^ |u e' 1 = 1,000 I u I' I 



max L o max o max' 



Now, if we take I U | = 1 f t and ou = 1.26 rad/sec (which corresponds to a 



period of 5 sec), then B = 0ol6 and u)' - 1.85 . Then, from Figure 3, 



It.' I = 1 . 9 and therefore, Ie I = 1,900 psi. Also, for the same tl) , 

 max max 



and lU I = 10 ft, 1e | = 20,000 psi. Similarly, for | U | = 19 ft and 

 ' o' max' ' f } 1 qI 



UD = 0.63 (which corresponds to a period of 10 sec), \T, | = 23,700 psi. 



The static stress distribution is linear, and for this cable and array without 

 any buoyancy, the maximum static stress (at the top of the cable) is 103,000 

 psi while its minimum value (at the bottom of the cable) is 33, 300 psi . 

 Stresses due to currents of the type considered in Section III are much smaller 

 than these static stresses. Even without determining the locations of the above 

 dynamic stresses, it is obvious that this cable will be able to withstand the 

 maximum total stress with a factor of safety of about 2 . If a larger factor of 

 safety is desired, the metallic cross-sectional area of the cable can be in- 

 creased and/or buoyancy in the cable and array can be utilized in order to de- 

 crease the large static stresses. However, if the static stresses are de- 

 creased below the dynamic stresses, the cable will buckle (see Section VI). 



20 



artbur H.ILittUJnt. 



S-7001-0307 



