The values o£ C^^ given in Table 7-3 show that Skjelbria (1960), 

 Dean and Aagaard (1970) and Evans (1970), used almost the same experimen- 

 tal data, and yet estimated different values of C^^. The same applies to 

 their determination of Cj^, but while the recommended choice of C^ 

 from Figure 7-58 is generally conservative, from Equation 7-46 the recom- 

 mended choice of Cyi^ for Rg > 5 x 10^ corresponds approximately to the 

 average of the reported values. This possible lack of conservatism, how- 

 ever, is not significant since the inertia force component is generally 

 smaller than the drag force component for design conditions. From Equa- 

 tions 7-30 and 7-31 the ratio of maximum inertia force to maximum drag 

 force becomes 



^im TT ^M D ^im 



= (7-47) 



^Dm 2 C^, H K^^ 



For example, if C^ «s 2 C^j and a design wave corresponding to 

 a/Hjy = 0.75 is assumed, the ratio ^im/^Dm ""^y ^^ written (using Figures 

 7-43 and 7-44 as 



"Dm 



D , „ 

 1.25 — (shallow-water waves) 

 H 



5.35 ~ (deepwater waves) 



(7-48) 



Since D/H will generally be smaller than unity for a design wave, 

 the inertia- force component will be much smaller than the drag- force com- 

 ponent for shallow-water waves, and the two force components will be of 

 comparable magnitude only for deepwater waves. 



7.316 Example Problem and Discussion of Choice of a Safety Factor . 

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



GIVEN : A design wave with height, H = 35 ft. and period, T = 12 sec, 

 acts on a pile with diameter, D = 4 ft. in water of depth, d = 85 ft. 



FIND : The wave force on the pile. 



SOLUTION : Compute, 



_H ^ 35 



gT2 (32.2) (12)2 



0.00755 , 



and 



d _ 85 



gT^ ~ (32.2) (12)2 



7-110 



0.0183 



