The following examples demonstrate the increased load-carrying capacity 

 when foam is added to the tires : 



(a) Example 1. If none of the tires are foamed, m = and m/n = 

 in equation (3) so that F ge( j = 13 kilograms per tire. Therefore, a 

 weight increase of approximately 13 kilograms per tire can be accom- 

 modated before the breakwater starts to submerge. 



(b) Example 2 . If all the tires are foamed, m = n and m/n = 1 

 above so that F gec i = 30 kilograms per tire. In this case, each tire 

 can carry approximately 30 kilograms of additional load for a total 

 reserve buoyancy of about 5300 kilograms per single-pipe module. 



4. Cost Estimates . 



Major construction components for the PT-1 module and their respective 

 costs as of mid-1980 are listed in Table 1. It should be noted that the steel 

 pipe accounts for nearly 60 percent of the total cost. Therefore, substantial 

 savings are possible if used pipe can be purchased, which was done for the 

 floating breakwater at the Mamaroneck site where used dredge pipe was obtained 

 at a fraction of the cost indicated in Table 1. As a precautionary measure, 

 steel pipe should be filled with foam before the end caps are welded into 

 place. The total component cost amounts to $19.60 per square meter of 

 breakwater. 



Table 1. Cost estimates of PT- Breakwater components. 



Module dimensions: 3.7 by 12.2 m (B = 12.2 m) 



Materials: Truck tires (9.00-18 and 10.00-20) 



Steel pipe (41-cm-diameter steel-pile pipe) 

 Conveyor-belt material (three-ply, 14 by 1.3 cm) 

 Nylon bolts, washers, and nuts (13 mm) 



Item Quantity Unit cost Total cost Cost/m 2 



Steel pipe 



Polyure thane foam 



(pipe plus 20 percent of tires) 



Tying material 

 (conveyor belt) 



Tires 

 (transportation cost) 



Nylon bolts, washers, and nuts 



Cost of breakwater $19.60 



(excluding mooring system and assembly) 



23 



2.2 m 



$43.00 



$524.60 



$11.60 



2.4 m 3 



75.00 



180.00 



4.00 



94 m 



1.15 



108.10 



2.40 



176 



0.25 



44.00 



1.00 



80 



0.35 



28.00 



0.60 



