When it is necessary to include the hydrostatic effects (e.g., seawalls), 

 the total force and moment are found by the expressions 



,2 



F , = ^-+ F (7-76) 



total 2 wave 



,3 



M , = ^+ M (7-77) 



total 6 wave 



where F^^ and ^ave ^^^ found from the design curves. The use of the 

 figures to determine forces and moments is illustrated in the following 

 example . 



************** EXAMPLE PROBLEM 31 *************** 

 GIVEN: 



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



(b) Wave height at the structure if the structure were not there H.= 1.5 

 m (5 ft). ^ 



(c) Depth at structure d = 3m (10 ft). 



(d) Range of wave periods to be considered in design T = 6 s (minimum) 

 or T = 10 s (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: 



H H 



i 1.5 i 1.5 



— = = 0.5 , = = 0.00A3 (T = 6 s) 



d 3 2 2 



gT 9.81 (6) 



Enter Figure 7-90 (because the wall is smooth) with the computed value of 

 H^/gT , and determine the value of H /H . from the curve for H ./d = 

 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.) 



H h 



i o 



For = 0.0043 — = 0.66 (T = 6 s) 



2 H 

 gT i 



Therefore, 



h = 0.70 (H.) = 0.66 (1.5) = 1.00 m (3.3 ft) (T = 6 s) 



7-170 



