* 



DETERMINATION OF MOORING LOAD AND 

 TRANSMITTED WAVE HEIGHT FOR A FLOATING TIRE BREAKWATER 



hy 

 Michael L. Giles and James W. Eckevt 



I . INTRODUCTION 



This report presents methods for predicting the transmitted wave 

 height and required anchor capacity for a floating tire breakwater (FTB) 

 using the FTB module concept proposed by the Goodyear Tire and Rubber Co. 

 (Candle and Fischer, 1977). The methods are based on prototype-scale 

 wave tank tests of the Goodyear module FTB (Giles and Sorensen, 1978). 



Because of the ease of module construction and availability of used 

 tires, this type of FTB provides an alternative means for sheltering 

 shorelines, docks, and boats from both storm and normal wave conditions. 

 In comparison to other types of floating or fixed breakwater structures, 

 the proposed module design has a relatively low cost. Because floating 

 breakwaters are most effective for short -period waves, this type of FTB 

 may best be used as protection for harbors of refuge and for shorelines 

 in which the waves are limited by fetch or water depths such as in large 

 coves, estuaries, and reservoirs. 



The FTB is assembled using individual 18-tire modules (Fig. 1) 

 measuring approximately 6.5 by 7.0 by 2.5 feet (2.0 by 2.2 by 0.8 meters). 

 The modules are constructed by stacking the tires in a 3-2-3-2-3-2-3 

 combination and threading tying lines through the tires as they are 

 stacked. An evaluation of various types of tying materials for both 

 freshwater and saltwater environments (Davis, 1977) has found that con- 

 veyor belting and unwelded open-link chain were the optimum choices for 

 corrosional resistance. Typically, the FTB has flotation material added 

 to the crown of each tire and two 2-inch-diameter (5 centimeters) holes 

 are punched in the bottom of each tire. The use of flotation material, 

 such as rigid urethane or polystyrene, will maintain uniform flotation 

 of the breakwater and will permit the use of severely damaged tires which 

 otherwise could not be used. The holes are to reduce the amount of sand 

 and debris which may accumulate in the tires. Additional details on the 

 construction of the individual modules and assembly of the modules to 

 form a complete breakwater are presented by Candle and Fischer (1977) and 

 by Kowalski and Ross (1975) . 



The data and design curves presented are applicable for wave heights 

 up to about 4.5 feet (1.4 meters), wavelengths between 30 and 165 feet 

 (9.5 and 50 meters), and water depths between 6.5 and 13 feet (2 and 4 

 meters). If design conditions are significantly different, then care and 

 engineering judgment should be used in applying these design procedures. 



II. DETERMINATION OF BREAKWATER WIDTH 



For specific site conditions, given the design incident significant 

 wave height, H. , wave period, T, water depth, d, and transmitted 



