the pile. Concrete mass anchors have the advantage of being relatively inex- 

 pensive with a practical burial in soft-bottom material. Many bottom loca- 

 tions have at least a few feet of soft or otherwise favorable material for 

 anchor placement. A concrete mass anchor is only capable of developing a 

 resistance to movement of about one-half its submerged weight if the ground is 

 firm enough to resist settling. Both concrete mass anchors and pile anchors 

 for floating breakwaters are discussed in Giles and Eckert (1979). 



(2) Anchor lines. Acceptable materials for a floating breakwater 

 anchoring system are synthetic fibers, chain, or wire rope. Design compar- 

 isons should consider cost, size, working strength, and elasticity. Wire rope 

 is economical but with low longevity; it does not stretch or absorb shock as 

 readily as other materials. Wire rope is available in many varieties and 

 yields the highest strength per cost, but requires replacement frequently 

 (Stormer, 1979). 



Chain is available in many grades and types of materials. For anchoring 

 purposes, Miller (1974a) recommends stud link primarily because of ease of 

 handling. Chain derives its energy absorption capabilities from the com- 

 ponents of weight and the resultant catenary effect which effectively func- 

 tions as a spring. Connection is easily provided at any point on its length. 

 Anchor chains which are not galvanized should be designed oversized to allow 

 for corrosion. This oversizing is beneficial because the weight gained yields 

 a deeper catenary curve and more absorption capability because of the spring 

 effect. Mooring chains and joints always experience repeated loading, causing 

 a decrease in strength from fatigue and a loss in chain diameter through abra- 

 sion and corrosion. Araki (1978) conducted preliminary investigations to 

 determine cumulative fatigue damage. 



Nylon, dacron, or polypropylene synthetic lines each have unique charac- 

 teristics to be considered, but nylon is more practical because of its energy 

 absorption nature (the fundamental purpose of the floating breakwater system). 

 The size of nylon lines is important because the elongation and resultant 

 lateral movement of the floating breakwater must be kept within reasonable 

 limits. The recommended factor of safety for synthetic lines is 4 to 5. 

 Miller (1974a) noted that pertinent to the design of a floating breakwater is 

 the availability of sufficient reserve strength for the rare storm which would 

 greatly exceed the normal working loads. Prototype observations indicate that 

 it would be a rare condition if the entire length of a floating breakwater 

 were loaded uniformly at a particular time. It is more probable that only a 

 small percentage of the total number of anchor lines will be fully loaded at 

 any time. 



IV. SLOPING-FLOAT (INCLINED PONTOON) BREAKWATER 



The sloping-float breakwater, proposed by Patrick (1951), consists of a 

 row of moored, flat slabs or panels which lean into the incident waves, and 

 whose mass distribution is such that, in still water, each panel has one end 

 resting on the bottom and the other protruding above the water surface. 

 Incoming surface gravity waves encounter the structure which occupies the 

 entire water column. Some energy may pass over the barrier (if the freeboard 

 is not high enough to prevent overtopping), some will usually pass under it, 

 and in an assembly of floats, some energy will pass through the gaps between 

 the floats. Waves in the lee of the structure exist largely because of the 

 induced motion of the float, which is resisted by inertia, gravity, and the 

 moorings. A proposed modification of the original concept (Patrick, 1951) is 

 the addition of legs to create a gap between the lower edge of the float and 



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