************** EXAMPLE PROBLEM *************** 

 GIVEN : 



(a) A vertical wall 10 feet high in a water depth of dg = 7.5 feet on 

 a nearshore slope of 1:20 (m = 0.05), and 



(b) design wave periods of T = 6 sec. and T = 10 sec. 



FIND : Determine the reduced force and overturning moment because of the 

 reduced wall height. 



SOLUTION : Calculations of the breaker heights, unreduced forces and 

 moments are given in preceding example problems. From the preceding 

 problems, 



Hj, = 8.4 ft. , (dj, = 8.9 ft. > dj , 



R = 16,900 Ibs./ft. , 



Ib.-ft. 

 M^ = 126,800 -T— (T = 6 sec.) 



and 



Hj, = 9.8 ft. , (dj, = 9.2 ft.>dj, 



R^ = 11,500 Ibs./ft. , 



Ibs.-ft. 

 M^ = 86,300 —J— . (T = 10 sec.) 



For the breaker with a period of 6 seconds, the height of the breaker 

 crest above the bottom is 



The value of b' as defined in Figure 7-77 is 6.7 feet (i.e., the 

 breaker height ti^ minus the height obtained by subtracting the wall 

 crest elevation from the breaker crest elevation). Calculate 



W (\i 



'^ = T7 = 0-798 . (T = 6 sec.) 



Hj, 8.4 



7-156 



