c. Flotation Materials . Floating breakwaters should be fail-safe if 

 specific compartments are filled with polystyrene or other foam flotation 

 materials. Certain compartments should be left open for weighting of the 

 structure to allow even flotation characteristics (Stormer, 1979); this would 

 be much simpler than adding flotation to a breakwater which was otherwise 

 overweighted. The method of providing flotation should allow for punctures 

 and leakage by including a redundancy in the form of bulkheads or simply the 

 interconnection of all components. The flotation material must be resistant 

 to, or protected from, impact and deterioration. Polystyrene foam is both 

 gasoline- and solvent-resistant, and should be specified for all uses in 

 floating breakwaters. 



d. Timber Components . Timber is both abundant and versatile in framing, 

 but the connection between members is always the weakness in the system. Two 

 timber members should be connected with long dapped joints, heavy bolts, and 

 large washers. All hardware should be hot-dip galvanized, and the timber 

 structure should be as continuous as possible (eliminating all unnecessary 

 joints). The mass, depth, and width of a floating breakwater should be as 

 great as economically allowable. The mass of a proposed pontoon-type struc- 

 ture consists of concrete supported by timber-framed floats. The timber, 

 hence, provides both a sound structure and a means of supporting the required 

 flotation. 



All timber used in a floating structure should be pressure-treated in 

 accordance with industrial standards. Any cuts or holes required after the 

 treatment should have similar solutions applied hot and forced to soak into 

 the wood. Miller (1974a) considers creosote the most effective substance for 

 use in the Pacific Northwest; however, copper-chrome-arsenate has been found 

 more resistant to borer attack elsewhere. The use of creosote in sunbathing 

 areas has been objectionable; thus, chemonite or pentachlorophenol treatment 

 is recommended for decking, with creosote used on those parts below the 

 waterline. 



e. Module Connections . All hardware and mechanical connections necessary 

 to join modules of a floating breakwater should be carefully sized to exceed 

 the strength of the anchor lines in retaining the structure. The connections 

 (shackles, clevises, swivels, bolts, pins, etc.) usually experience the 

 greatest wear and motion and should have secondary methods of loss prevention 

 such as cotter pins or double nuts. Custom-designed and fabricated connecting 

 devices have been found to be the best and most economical, but compatible 

 materials can be used to lessen galvanic action. Under load conditions 

 equivalent to those of actual breakwaters, Araki (1978) performed tests on 

 chains, pin joints, and boss holes in seawater tanks to determine the amount 

 of abrasion anticipated after a finite number of loadings. 



Different schemes at different locations have been used in efforts to 

 develop the most appropriate connector of large concrete pontoon-type units. 

 Figure 52 shows the connection used at Sitka, Alaska. In this system, chains 

 at the top and at the bottom pull the modules together and compress the square 

 rubber bumpers slightly. The rubber bumpers are bolted to one module but not 

 to the other; hence, any tension in the chains is not transmitted to the 

 rubber bumpers. Wooden blocks were also placed between the concrete modules 

 and the bumpers. This system is believed to be an improvement over the system 

 previously used at Tenakee Springs, Alaska (Adee, 1975b). 



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