Figure 3. Orientation of PT- Breakwater. 



(a) densely spaced tires, (b) tire-armored longitudinal stiffeners (frequently 

 steel pipes) , and (c) flexible connections and binding materials (no steel-to- 

 rubber connections). The orientation of the pipes with respect f:o the inci- 

 dent wave train is shown in the drawing in Figure 3, with major structural 

 features of the breakwater shown in the module schematic in Figure 4 and the 

 definition sketch in Figure 5. 



1 . Breakwater Modules and Components . 



Two versions of the PT- Breakwater, designated as the PT-1 and PT-2 mod- 

 ules, were tested in the large wave tank at CERC (Fig. 6). The PT-1 module, 

 which is the most massive of the two due to its composition of truck tires and 

 steel pipes, is shown in the foreground. The PT-2 module is constructed from 

 car tires and used telephone poles. From the detailed drawing of the PT-1 

 module (Fig. 4), several important structural features of the breakwater 

 emerge : 



(a) A series of parallel conveyor-belt loops receive all lateral 

 loads (at right angles to the direction of wave motion), supports all 

 tires that are not "riding" on the pipe, and couples one module to 

 the next . 



(b) Wave-induced hydrodynamic loads are ultimately transferred 

 from tire strings to the tire-armored steel pipe. This takes place 

 in stages. Wave action displaces tire strings and belt loops in the 

 direction of the wave motion (along the pipe) causing the pipe tires 

 to slide along the pipe and become compressed as they transfer their 

 load to the tire retainer at the end of the pipe (Figs. 4 and 7). 



(c) The pipe itself effectively floats in a dense matrix of 

 flexibly connected tires. 



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