CERC.1979. PT-1 BRERKWRTER WITH MOORING TYPES 1.2.3: DEPTH- 4.6 M 



00 



5° 



+ - 



+ 



D= 102 cm 



^.00 



0.50 



1 .00 



1.50 2.00 2.50 3.00 

 RELATIVE WflVELENGTH 1 ' L/B 



Figure 34. Wave transmission data for PT-1 breakwater (d = 4.7 m) . 



D/d) and breakwater geometry (aspect ratio, B/D, and pipe spacing, G/D). 

 For design purposes, the transmission characteristics of each breakwater are 

 summarized in the form of a single wave height transmission curve. This curve 

 corresponds to a wave steepness of H/L = 0.04 (a moderate value frequently 

 encountered in practice) and different values of D/d. Although much data 

 have been obtained at wave steepness other than 0.04, indicating that the 

 transmission ratio, C t , generally decreases with increasing wave steepness, 

 the available data are not adequate for defining transmission curves for wave 

 steepness other than 0.04. Nevertheless, the influence of wave steepness has 

 been preserved to a large extent by grouping the data according to steepness 

 categories; in Appendix C the value of H/L is actually listed next to each 

 data point. Appendix C should be particularly useful for design cases with 

 wave steepness near the extremes encountered in nature, either high or low 

 (e.g., H/L larger than 0.08 or less than 0.02), since deviations from the 4- 

 percent design curve may then become significant. The wave transmission data 

 in Appendix C have also been segregated with respect to the type of mooring 

 system installed, but it was found that this had no discernible influence on 

 wave transmission characteristics. It is therefore permissible to combine the 

 data for all of the mooring systems as has been done in Figure 34. 



a. PT-1 Breakwater . Wave transmission data for the PT-1 module (truck 

 tires, steel pipe) are shown in Figures 34 and 35 for two water depths, D/d - 

 0.22 and 0.51. In both cases the transmission ratio, C^, increases mono- 

 tonically with relative wavelength L/B. The breakwater is very effective 



38 



