2 

 F. (D = 0.6 m) = F. (D = 0.3 m) ^^'^\ = 1,875 (4) = 7,500 N (1,686 lb) 



zm vm (0.3)^ 



F = (D = 0.6 m) = F (D = 0.3 m) ^ = 3,255 (2) = 6,510 N (1,464 lb) 

 DM DM U • J 



The new value of W from equation (7-41) is 



V = 2.0(0.6) ^ 



^ C H 1.2(3) ^'-^-^ 



D 



and the new values of cj) and a are 



m m 



(t) = 0.15 

 m 



and 



a = 0.10 



m 



Therefore, from equation (7-42) 



[f ] 0.6 -m diam. = (f. w C H D 



m m D 



(F ) 0.6 -m diam. = 0.15 (10,047) (1.2) (3)^ (0.6) = 9,766 N (2,195 lb) 

 m 



and from equation (7-43) 



(m ) 0.6 -m diam. = a wC H^Dd 



m m D 



(m ] 0.6-m diam. = 0.10 (10,047) (1.2) (3)^ (0.6) (30.0) = 

 '" 195.3 kN-m (144,100 ft-lb) 



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



d. Transverse Forces Due to Eddy Shedding (Lift Forces) . In addition to 

 drag and inertia forces that act in the direction of wave advance, transverse 

 forces may arise. Because they are similar to aerodynamic lift force, 

 transverse forces are often termed lift foraest although they do not act 

 vertically but perpendicularly to both wave direction and the pile axis. 



Transverse forces result from vortex or eddy shedding on the downstream 

 side of a pile: eddies are shed alternately from one side of the pile and 

 then the other, resulting in a laterally oscillating force. 



Laird et al. (1960) and Laird (1962) studied transverse forces on rigid 

 and flexible oscillating cylinders. In general, lift forces were found to 

 depend on the dynamic response of the structure. For structures with a 

 natural frequency of vibration about twice the wave frequency, a dynamic 

 coupling between the structure motion and fluid motion occurs, resulting in 



7-132 



