Figure 16. PT-1 module ready for lift into wave tank. 



3. Breakwater Buoyancy. 



a. Pipe Buoyancy Test . A simple buoyancy test was executed by resting 

 steel I-beams on top of one of the tire-armored pipes of the PT-1 module until 

 total submergence was attained (i.e., crown of tires just at the water sur- 

 face, case B in Fig. 17). Starting from the static, no-load equilibrium 

 position of the breakwater (i.e., crown of pipe at water level and interior 

 of the tire vented to atmosphere, case A), two steel I-beams, each 10.7 meters 

 long and weighing 98 kilograms per meter, were placed onto the tire-armored 

 pipe. These beams provided the loading needed to attain total submergence of 

 the pipe-tire unit. In each case, equilibrium demands that 



where 

 F 



F e 

 F a 



F F 

 W. 



tw 



"ta 



F + n(W ta + W tw ) + F e = F p + nF a 



added external load 



extraneous loads (from mooring system, etc.) 



buoyancy force per tire due to entrapped air 



net buoyant force due to pipe (lift minus weight) 



weight of tire segment submerged in water 



weight of tire segment in air 



number of tires on pipe 



(1) 



20 



