S = a N^ 



J , (6.11) 



v Pi 



In Equation 6. 1 1, N„„ = H^„ /AD„^q is the stability number based on the zeroth moment 

 wave height, the test duration / for constant wave conditions is normalized by the peak 

 period, and ap and b are again empirical coefficients that will be obtained from data. It 

 is noted that Equations 6.10 and 6. 1 1 assume 5 = at f = and constant wave 

 conditions. 



The expression for a^ in Equation 6. 10 can be found from Equation 6.9 

 where P = 0.4 for conventional rubble-mound breakwaters. For Q = 1.2, P = 0.4, and 

 cot = 2, a^ = 0.003 for Equation 6.10 ifb = 0.5 is applicable to the present long 

 duration tests. Van der Meer (1988) analyzed the five long duration tests with A^„. up to 

 15,000 conducted by Thompson and Shuttler (1976) and obtained the term S/N„°-^ in 

 Equation 6.9 for A^^ = 1,000-8,500. His data analysis indicated b < 0.5 for A^^ > 8,500. 

 In the following, the values of a^ and b are calibrated for this experiment where N^ = 

 60,000 for Series A' and N,, = 18,000 for Series B' and C. 



The empirical relationship in Equation 6.10 is limited to damage due to 

 incident irregular waves with constant H^ and T„ starting from S=Oatt = 0. As a 

 result, these formulas and other existing formulas are intended for prediction of damage 

 during the peak of a design storm. In order to develop an empirical procedure for more 



122 



