Therefore from Equation 7-32, 



M,-m = F,-m ^ S,.^ = 384 (15) (0.81) = 4,670 Ib.-ft., 

 and from Equation 7-33, 



^Dm = ^Dm'^ ^Dm = 1,580 (15) (1.02) = 24,170 Ib.-ft. 



The value of a^ is found by interpolation between Figures 7-53 and 

 7-54 using W = 0.29, H/gT^ = 0.0031 and d/gT^ = 0.00466. 



Figure 7-53 W = 0.1 ; a^ = 0.34, 



Interpolated Value W = 0.29; a^ «^ 0.35. 



Figure 7-54 W = 0.5 ; a^ = 0.36. 



The maximum total moment about the mudline is found from Equation 7-36. 

 Mm = "m w C^H^Dd. 



M^ = 0.35(64) (0.7) (lO)Ml) (15) = 23,520 Ib.-ft. 

 say 



M^ = 23,500 Ib.-ft. 



The moment arm, measured from the bottom, is the maximum total moment 

 M^ divided by the maximum total force F^; therefore. 



M 



__m _ 23,520 

 F^ " 1,635 



14.1 ft. 



If it is assumed that the upper 2 feet of the bottom material lacks 

 significant strength, or if it is assumed that scour of 2 feet occurs, 

 the maximum total horizontal force is unchanged, but the lever arm is 

 increased by about 2 feet. The increased moment can be calculated by 

 increasing the moment arm by 2 feet and multiplying by the maximum 

 total force. Thus the maximiom moment is estimated to be 



m)2 ft. below mudline 



say 



(^m)2 ft. below mudline = 26,300 Ib.-ft. 



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



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



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



GIVEN : A design wave with height H = 10 ft. and period T = 10 sec. 

 acts on a vertical circular pile with a diameter D = 1 ft. in a 

 depth d = 100 ft. Assume % =2.0 and Cp = 1.2 



7-92 



