*************** EXAMPLE PROBLEM 28*************** 



GIVEN ; A design wave with height H = 10.0 m (32.8 ft) and period T = 12 s 

 in a depth d = 26.0 (85.3 ft) acts on a pile with a diameter D = 1.25 m 

 (4.1 ft). (Assume Airy theory to be valid.) 



FIND ; The variation of the total force on the pile as a function of distance 

 from the wave crest. 



SOLUTION ; From an analysis similar to that in Section III,l,e, 



C^=0.7 



and 



C = 1.5 



m 



From Figures 7-71 and 7-72, using the curve for Airy theory with 



d 26.0 



= 0.0184 



2 2 



gT 9.8 (12) 



K . = 0.38 ; K = 0.20 



im Dm 



and from equations (7-37) and (7-38), 



2 

 F = 1.5 (1025.2) (9.8) "^^^'^^^ (10.0)(0.38) = 70.3 kN (15,800 lb) 

 im ^ 



F = 0.7 (0.5)(1025.2)(9.8)(1.25)(10.0)^ (0.20) = 87.9 kN (19,800 lb) 



Dm 



Combining equations (7-29) and (7-33) gives 



F = F sin e 



i im 



and combining equations (7-30) and (7-34) gives 



F = F cos e 1 cos 6 I 

 D Dm ' ' 



where 



2lTX 2Tlt 



" — — z — — — ;;; — 



The wavelength can be found from Figure 7-68, 



L « L = 171 m 



A 



7-152 



