the structure geometry. This method also provides no indication of the severity of 

 damage as characterized by the profile shape. 



Jackson (1968) gave damage due to regular waves in terms of the WES 

 eroded volume definition of damage. Jackson's damage values, given in Table 7-9 in 

 the SPM, have been widely used to predict damage but are limited to regular waves with 

 damage starting from an undamaged structure. Also, the damage is not given as a 

 function of time, which is critical for determining the reliability of a structure. 



Broderick and Ahrens (1982) and Van der Meer (1988) defined a 

 dimensionless damage index using profile data as 



A. A. 



Ms, 



k P" ; 



d'so (3.1) 



where 



Ag = eroded volume per unit length or cross-sectional eroded area 



M50 = mass of median armor unit in mass distribution 



p^ = armor unit density 

 where their variable nomenclature has been modified to avoid confusion. Broderick and 

 Ahrens stated that A^ was calculated from the profile data by determining the difference 

 between before and after testing profiles. The difference in Broderick and Ahrens' 

 method from the traditional eroded volume method was that they nondimensionalized 



36 



