Total force and moment is given by, 



R^ = R«, + Re = 1>560 + 1,250 = 2,810 Ibs./ft. 



Ib.-ft. 

 M, = M„ + M, = 4,870 + 2,590 = 7,460 —r- 

 t m s ^ ' ft 



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



7.35 EFFECT OF ANGLE OF WAVE APPROACH 



When breaking or broken waves strike the vertical face of a structure 

 such as a groin, bulkhead, seawall or breakwater at an oblique angle, the 

 dynamic component of the pressure or force will be less than for breaking 

 or broken waves that strike perpendicular to the structure face. The 

 force may be reduced by the equation, 



R' = R sin^a (7-103) 



where a is the angle between the axis of the structure and the direction 

 of wave advance, R' is the reduced dynamic component of force, R is 

 the dynamic force that would occur if the wave hit perpendicular to the 

 structure. The development of Equation 7-103 is given in Figure 7-81. 

 Force reduction by Equation 7-lOZ should he applied only to the dynamic 

 wave-force component of breaking or broken waves and should not be 

 applied to the hydrostatic component. The reduction is not appliaable 

 to rubble structures . The maximum force does not act along the entire 

 length of a wall simultaneously; consequently, the average force per 

 unit length of wall will be lower. 



7.36 EFFECT OF A NONVERTICAL WALL 



Fonnulas previously presented for breaking and broken wave forces 

 may be used for structures with nearly vertical faces. 



If the face is sloped backward as in Figure 7-82 (a), the horizontal 

 component of the dynamic force due to waves breaking either on or seaward 

 of the wall should be reduced to, 



R" = R' sin2 d (7-104) 



where 9 is defined in Figure 7-82. The vertical component of the 

 dynamic wave force may be neglected in stability computations. For 

 design calculations, forces on stepped structures as in Figure 7-82 (b) 

 may be computed as if the face were vertical, since the dynamic pressure 

 is about the same as computed for vertical walls. Curved nonreentrant 

 face structures (Fig. 7-82 (c)) and reentrant curved face walls (Fig. 

 7-82 (d)) may also be considered as vertical. 



7-164 



