III. 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 7-66 

 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 Wove Action 



NON-BREAKING 

 Seaward of surf zone 



BROKEN 

 Shoreward of surf zone 



PILE SUPPORTED 

 Piers, offshore platforms 



WALLS 

 Seawalls, bulkheads, etc. 



RUBBLE 

 Groins, jetties, etc. 



Classification by Type of Structure 



Figure 7-66. Classification of wave force problems by type of wave action and 

 by structure type. 



Rubble structure design does not require differentiation among all three 

 types of wave action; problem types shown as IR, 2R, and 3R on the figure need 

 consider only nonbreaking and breaking wave design. Horizontal forces on pile- 

 supported structures resulting from broken waves in the surf zone are usually 

 negligible and are not considered. Determination of breaking and nonbreaking 

 wave forces on piles is presented in Section 1 below. Forces on Piles. Non- 

 breaking, breaking, and broken wave forces on vertical (or nearly vertical) 

 walls are considered in Sections 2, Nonbreaking Wave Forces on Walls, 3, 

 Breaking Wave Forces on Vertical Walls, and 4, Broken Waves. Design of rubble 

 structures is considered in Section 7, Stability of Rubble Structures. 

 NOTE: A careful distinction must be made between the English system use of 

 pounds for weight, meaning force, versus the System International (SI) use of 

 newtons for force. Also, many things measured by their weight (pounds, tons, 

 etc.) in the English system are commonly measured by their mass (kilogram, 

 metric ton, etc.) in countries using the SI system. 



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