These new coefficients are listed as a,, 61, Ci and d^ in Table 4.3. This fitted curve to the data is con- 

 sidered to be valid between Yg/rfj^^x = and ^effmax = 1-25 ilYgpFM^x = 2.5). The results in the 

 table can be employed as inputs to a predictive model for the strumming oscillations of a flexible cable 

 according to the methods described in Appendices D and E. However, it should be noted that the 

 coefficient Qf represents only the excitation force on the structure or cable. For vibrations in water it 

 is necessary to have an accurate and precise representation of the coefficients of the added mass, hydro- 

 dynamic damping and hydrodynamic inertia forces. These coefficients are not as well characterized as 

 Qf, but they can be derived from the total force measurements of Sarpkaya (28), for example, as 

 shown in Table 2.3 and Appendix E. 



Table 4.3 Excitation Force Coefficient C/^; 

 data from Fig. 4.9 



Force coefficient: Q^ = 0^ + b^ Yeff.max + Ci ^eff.max + ^1 Yeffmax 



where a^ = 0.12, ft, = 2.12, Ci = -3.57, rf, = 1.45 

 and the standard deviation of the curve cr =0.1. 



Enective displacement: I^effm^a'^ ' >/ = ;i 



7/ /,- 



In terms of Yf^^xl ^-^ 



Cle\-y^,, = «i + (*i/r,) ^YmaxID) + icjy}) (Y^Ax/Dy + id.lyj) (Y^ax/D)' 



where the factor y, is evaluated_for a given set of end fixities, i.e. free-pinned, pinned-pinned, 

 clamped-ciamped, etc. Hence Y^^xl ^^ 'S the peak displacement along the beam. The factor 

 -y, can be calculated from the data listed in Table El. 



+ Note that this form of the equation is slightly different than introduced by Blevins (71) as given in equation (4.3.5a) 



Several handbooks and catalogues of relevant data are available to augment the results contained 

 in this report. These include a survey of steady drag coefficients for cables subjected to cross flow 

 currents (73), a detailed handbook of hydrodynamic coefficients for moored array components (74), 

 and a book in which the practical aspects of moored cable and buoy engineering are discussed (75). 

 The report by Dalton (73) is a compilation of steady drag coefficients for stranded steel and synthetic 

 fiber cables. These data are tabulated according to the source and in each case a critical assessment is 

 made concerning the reliability of the experimental findings. The report by Pattison, Rispin and Tsai 



95 



