1.0 

























*o\ 



\ 

 \ 



















v 



S ^\ 



o 









0.4 









O^ \ 



















■^SL 



















«o 



^^-^ 



^o^ 





0.2 















?** 









Anchor Ch lins Uncro ised 

 Anchor Ch lins Cross :d 





2 









o 









0.1 



0.7 



0.2 03 0.4 0.5 0.6 



Ratio of Breakwater Width-to-h'avelength, W/L 



COEFFICIENT OF TRANSMISSION (Ct) 

 note; numbers beside oata points VERSUS RELATIVE WIDTH (W/L) 



INDICATE THAT THE NUMBER TWO-DIMENSIONAL TESTS 



OP DATA POINTS EXCEEDS ONE p| _ AN 3 ^.^ ^^ 



Figure 44. Coefficient of transmission, C t , versus relative break- 

 water width, W/L, results from two-dimensional experi- 

 mental investigation of Alaska-type floating breakwater, 

 Olympia Harbor, Washington (after Carver, 1979). 



section of a model breakwater is subjected to monotonic waves and the force 

 parameters are measured. Anchor forces scaled up from such tests are apt to 

 be unrealistically large (Richey and Adee, 1975) because: (a) the elasticity 

 and restraint conditions are not precisely simulated, (b) the model is usually 

 short with respect to the crest lengths of the incident wave, and therefore 

 receives the wave over its full length, and (c) the regular, monotonic waves 

 can force the breakwater to translate to the end of its tether, taking up all 

 slack in the anchor system, at which time high forces develop. In the natural 

 random wind-wave environment, the probability of a series of waves striking 

 the full length of a floating breakwater is very low. Anchor forces measured 

 at Tenakee Springs, Alaska, indicated the large forces to be 7,146 pounds for 

 a 60-foot module, or about 6 percent of the weight of the structure. 



Richey and Adee (1975) combined the studies of Sorensen (1967) on ship 

 waves and Stramandi (1974) on breakwater response of ship waves to assess the 

 ship wave problem in the Bar Point Harbor site. When vessels travel at speeds 

 less than 8 knots, wave heights exceeding 1 foot would be exceptional; the 

 waves would strike the breakwater at an appreciable angle, so the transmission 

 coefficient of 0.3 or less would be appropriate. Therefore, the transmitted 



80 



