3. Basic Floating Breakwater Groups . 



Jones (1971) and Richey and Nece (1974) recognized at least 60 different 

 floating breakwater configurations. Geometric and functional similarities 

 among these various configurations, however, allow for logical classification 

 into basic groups based on fundamental features. 



a. Pontoon Floating Breakwaters . This group of prismatic structures (sin- 

 gle pontoon, double pontoon, or other variations) contains the simplest forms 

 of floating breakwaters, and has been dealt with extensively by experimental- 

 ists and theorists. The prismatic form offers the best possibilities for 

 multiple use such as walkways, storage, boat moorings, and fishing piers. 

 Catamarans also logically fit into this group. Several factors in addition to 

 mass contribute to the performance of pontoon-type breakwaters. The radius of 

 gyration, antirolling devices, and the depth of submergence influence wave 

 attenuation characteristics. Furthermore, as the ratio of breakwater width-to- 

 wavelength increases, the pontoons tend to deform, absorbing wave energy in the 

 bending process. The design of the double-pontoon system attempts to combine 

 relatively large mass and large radius of gyration, and pontoons of this 

 configuration are capable of functioning as floating piers where cargo may be 

 unloaded. In this case, the stability and performance of the structure under 

 various loading conditions would be a prime consideration in design. 



b. Sloping-Float (Inclined Pontoon) Breakwaters. The sloping-float break- 

 water concept is a wave barrier that consists of a row of moored, flat slabs or 

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

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

 Preliminary tests and experience indicate that waves in the lee of the struc- 

 ture will exist largely because of the induced motion of the float, which is 

 resisted by inertia, gravity, and the moorings. The U.S. Navy is currently 

 interested in a hollow, steel barge adaptation (a pontoon barge or causeway 

 section) which appears to have acceptable dimensions and mass. The U.S. Army 

 Engineer Waterways Experiment Station (WES) is conducting an experimental 

 investigation into the possibility of utilizing the sloping-float breakwater to 

 provide a temporary protection to dredges and work boats in the nearshore open- 

 ocean region. 



c. Scrap-Tire Floating Breakwaters . Used automobile and truck tires are 

 accumulating at an enormous rate, and the seemingly physical indestructibility 

 of these abandoned tires has historically posed a problem of pollution-free 

 methods of disposal. The rubber industry is constantly seeking new and inno- 

 vative methods for utilizing these wornout tires. Coastal engineers have long 

 been interested in resilient energy absorption mats for shore protection, and 

 the use of scrap tires as floating breakwaters has been investigated intermit- 

 tently for the past 20 years. Stitt and Noble (1963) developed and patented a 

 geometric assembly configuration known as the "Wave-Maze," and the Goodyear 

 Tire and Rubber Company has investigated extensively the use of modular ele- 

 ments formed by securing together bundles of tightly interlocked scrap tires. 

 Harms (1979a) experimentally investigated a concept known as the "Wave-Guard" 

 (now referred to as the "Pipe-Tire" structure) which utilized massive logs 

 (telephone poles or steel pipes) as structural components with the scrap tires 

 threaded onto the poles. These three basic designs have received the greatest 

 attention from an experimental investigation standpoint. 



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