WAVE TRANSMISSION AND MOORING-FORCE CHARACTERISTICS 

 OF PIPE-TIRE FLOATING BREAKWATERS 



by 



Volkev W. Harms, Joannes J. Westevink, 



Robert M. Sorensen, and James E. MaTamany 



I. INTRODUCTION 



This report presents methods for constructing a recently developed float- 

 ing breakwater that consists largely of scrap pneumatic-tire casings, and 

 also provides basic data for the design of such structures. The idea of con- 

 structing floating breakwaters almost entirely from scrap tires was originally 

 conceived two decades ago by R.L. Stitt and resulted in a patent for the wave- 

 maze floating tire breakwaters (Stitt, 1963; Kamel and Davidson, 1968). More 

 recently, this concept was adapted in the development of the Goodyear floating 

 tire breakwater (Kowalski, 1974; Candle, 1976). Both these breakwaters 

 are flexible in all directions since there are no rigid structural members 

 utilized. The Goodyear module differs from the Wave-Maze in the size of the 

 tires used (automobile as opposed to truck tires) , geometric arrangement of 

 the tires (single-layer upright versus triple-layer "sandwich"), and binding 

 materials and techniques used (typically conveyor-belt loops as opposed to 

 bolted-tire connections). A number of floating breakwaters of both types have 

 been installed on the Great Lakes, the east and west coasts of the United 

 States, and overseas, with various levels of success. 



Although the installation of floating breakwaters is frequently favored 

 over bottom-resting structures for a number of environmentally related reasons 

 (e.g., Impact on water circulation, fish migrations), the principal reason for 

 considering floating breakwaters made of tires is their relatively low cost. 

 For small marinas of less than 100 boat slips, floating breakwaters are fre- 

 quently the only wave protection system that is economically feasible with 

 costs ranging from $10 to $100 per horizontal square meter of breakwater. At 

 the same time, it must be recognized that floating tire breakwaters provide 

 less wave protection, are less rugged, and have lower extreme event survival 

 capabilities than conventional bottom-resting structures, such as rubble-mound 

 and sheet-pile breakwaters. A comparison of knowledge acquired from field 

 installations and prototype-scale laboratory tests suggests that the Goodyear 

 and Wave-Maze floating tire breakwaters should be limited to semiprotected 

 sites, or short fetch applications (e.g., 10 kilometers or less), with signif- 

 icant wave heights below 0.9 to 1.2 meters. At locations with severer wave 

 climates (larger wave height and period), several limitations have been 

 encountered with regards to: 



(a) Structural Integrity . The response behavior of wave-induced 

 mooring loads increases approximately with the square of the wave 

 height. While under severe wave action the following problems have 

 been encountered: (1) modules connected to the seaward mooring lines 

 separate because of excessive loads, (2) anchors fail or "walk" 

 because of the large mooring forces, (3) flotation material is lost 

 from individual tires because of the excessive stretching and twist- 

 ing, and (4) tire connection and binding materials reach their fail- 

 ure limit. 



