By a similar analysis for an impermeable breakwater, using Figures 7-34 

 and 7-35, 



— « 0.33, 

 H, 



and 



H = (0.33) H. = 0.33(6) = 1.98 ft. , say 2 ft. 



The presence of an impermeable core in this instance does not provide 

 a significant decrease in transmitted wave height. Most of the wave 

 energy is transmitted by overtopping for the example conditions. 



************************************* 

 7.3 WAVE FORCES 



The study of wave forces on coastal structures can be classified in 

 two ways; (a) by the type of structure on which the forces act and (b) by 

 the type of wave action against the structure. Fixed coastal structures 

 can generally be classified as one of three types: (a) pile supported 

 structures such as piers and offshore platforms, (b) wall type structures 

 such as seawalls, bulkheads, revetments and some breakwaters, and (c) 

 rubble structures such as many groins, revetments, jetties and breakwaters. 

 Individual structures are often combinations of these three types. The 

 types of waves that can act on these structures are nonbreaking, breaking 

 or broken waves. Figure 7-38 illustrates the subdivision of wave force 

 problems by structure type and by type of wave action, and indicates nine 

 types of force determination problems encountered in design. 



Classification by Type of Wave Action 



NON-BREAKING 

 Seaward of surf zone 



BROKEN 

 Shoreward of surf zone 



PILE SUPPORTED 

 Piers, of fstiore platforms 



WALLS 

 Seawalls, buiktieods, etc. 



RUBBLE 

 Groins, jetties, etc. 



Classification by Type of Structure 



Figure 7-38. Classification of Wave Force Problems by Type of 

 Wave Action and by Structure Type 



7-63 



