(b) Breakwater Size . As with all breakwaters, the size of a 

 floating tire breakwater is site specific. The dimension of the 

 breakwater in the direction of wave propagation (width or beam) must 

 generally be at least as large as the locally predominant wavelength 

 (design wave). This implies that a very large breakwater will be 

 required at sites with long period waves, which not only increases 

 the breakwater's cost but also may not be feasible because of space 

 limitation. 



(c) Buoyancy. Portions of the breakwater configuration may begin 

 to sink If individual tires lose their flotation material (e.g., 

 caused by stretching and twisting while under high loads) or if the 

 structure gains too much weight with time (caused by deposition of 

 suspended sediments in the tire casings or excessive marine growth) . 



In an attempt to improve on the design characteristics of the floating 

 breakwaters discussed above, another wave protection concept utilizing 

 pneumatic tire casings as the major construction material has recently been 

 developed by the senior author at the State University of New York at Buffalo 

 (Harms and Bender, 1978; Harms, 1979a). It is referred to as the Pipe-Tire 

 Breakwater ( PT- Breakwater ) , or Harms Breakwater, and is basically a hybrid 

 structure with massive, rigid, cylindrical members (e.g., steel or concrete 

 pipes) embedded in a flexible matrix of scrap tires. Experiments performed 

 with several small-scale PT-Breakwater models (Harms, 1979b) and one full- 

 scale breakwater demonstrated that this design provides significantly more 

 wave protection than the Goodyear or Wave-Maze breakwaters constructed of 

 equal size. These early laboratory tests also suggested that a full-scale 

 PT-Breakwater would have superior extreme event survival capabilities, while 

 preliminary calculations indicated that costs would remain low enough for this 

 wave protection system to be economically attractive. 



Because of the PT-Breakwater 's potential contribution to low-cost wave 

 protection, prototype-scale experiments over a wide range of wave conditions 

 were conducted in a joint test program between the State University of New 

 York at Buffalo and the U.S. Army Coastal Engineering Research Center (CERC). 

 Full-scale tests, which are the subject of this report, were conducted in the 

 large wave tank at CERC. Investigations were aimed at defining the wave 

 transmission and mooring-force characteristics of PT-Breakwaters ; it was also 

 intended that structural failure modes be analyzed, should it be possible to 

 induce them within the range of wave conditions that could be generated in the 

 tank. 



Figures 1 and 2 provide a general impression of a floating PT-Breakwater. 

 This field installation at Mamaroneck, New York, is based on the PT-1 module 

 discussed in this report; it is constructed of truck tires with steel pipes 

 serving as the structural members and flotation chambers. The orientation of 

 the pipes with respect to the incident wave train is shown in Figure 3. 



II. THE PIPE-TIRE BREAKWATER 



The PT-Breakwater is basically a mat composed of flexibly interconnected 

 scrap tires, floating near the surface, into which massive cylindrical members 

 are inserted to provide stiffness in the direction of wave motion and to serve 

 as buoyancy chambers. Major structural features of the PT-Breakwater are 



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