evaluate h^ , F , and M , even though a rubble base will reduce the wave 



reflection coefficient of a structure by dissipating some incident wave 



energy. The values of h^j , F , and M used in this example were 

 determined in Example Problem 31. 



y^ = 5.5 m 



(T = 6 s) 

 y^ = 2.5 m 



Compute b/y for each case, remembering that b now represents the height 

 of the foundation. 



_b = 2^ = 0.491 

 Ye 5.5 



(T = 6 s) 



— = ^ = 1.08 > 1.0 

 yt 2.5 



Enter Figure 7-97 with the computed values of b/y , and determine corre- 

 sponding values of (1 - Xf) and (1 - r^) . For the 6-second wave, 



^ = 0.491; (1 - r.] = 0.26; (l - r^) = 0.52 

 and 



^> 1.0; [1 - r^] = 0.0; (l - r^] = 0.0 



From equation (7-82), 



F" = 0.26 (101.7) = 26.5 kN/m (1,820 lb/ft) 



(T = 6 s) 

 E].' = 0.0 (17.1) = kN/m 



For the 10-second wave, a similar analysis gives 



(T = 10 s) 



F^' = 30.8 kN/m (2,100 lb/ft) 



F^' « kN/m 

 The overturning moments about point A are, from equation (7-83) 

 [V^\ = 0.52 (163.8) = 85.2 kN-m/m (19,200 ^^~^^ ) 



[}^\ = 0.0 (11.8) = 



(T = 6 s) 



kN-m 



m 



7-179 



