When the trough is at the wall, pressure increases from zero at the water 

 surface to wd — p at the bottom. The approximate magnitude of wave 



force may be found if the pressure is assumed to decrease linearly from 

 the free surface to the bottom when either the crest or trough is at the 

 wall. Figures 7-65 through 7-70 permit a more accurate determination of 

 forces and moments resulting from a nonbreaking wave at a wall. Figures 

 7-65, 7-66, and 7=67 show the dimensionless height of the clapotis orbit 

 center above Stillwater level, dimensionless horizontal force, and 'limen- 

 sionless moment about the bottom of the wall for a reflection coefficient, 

 X = 1. Figures 7-68 through 7-70 represent identical dimensionless param- 

 eters for X = 0.9. The use of the figures to determine forces and moments 

 is illustrated in the following example. 



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

 GIVEN : 



(a) Smooth-faced vertical wall (x = 1.0). 



(b) Wave height at structure if structure were not there, 

 % = 5.0 feet. 



(c) Depth at structure, d = 10.0 feet. 



(d) Range of wave periods to be considered in design, 

 T = 6 sec. (minimum) T = 10 sec. (maximum) 



FIND : The nonbreaking wave force and moments against a vertical wall 

 resulting from the given wave conditions. 



SOLUTION : Details of the computations are given for only the 6-second 

 wave. From the given information, compute H-/d and H-/gT^ for the 

 design condition: 



^i 5.0 H; 5.0 



— = = 0.5 , — - = ;- = 0.0043. (T = 6 sec.) 



d 10.0 gT^ 32.2 (6)2 ^ 



Enter Figure 7-65 (because the wall is smooth) with the computed value 

 °f H'/gT^, and determine the value of h^/H- from the curve for 

 )^^lo. = 0.5. (If the wave characteristics fall outside of the dashed 

 line, the structure will be subjected to breaking or broken waves, and 

 the method for calculating breaking wave forces should be used.) 



For -— = 0.0043, p = 0.70. (T = 6 sec.) 



Therefore, 



h^ = 0.70 (H,) = 0.70(5.0) = 3.5 ft. (T = 6 sec.) 



7-130 



