c. Wave directionality. 



d. Wave grouping. 



e. Dolos position on breakwater and in armor layer. 



f. Structure slope. 



g. Structure porosity. 



The range of values of design interest for the first five items listed above 

 for the Crescent City case are contained implicitly in the pulsating design 

 distribution. For general application of this design procedure, although all 

 of the variables listed above may have a significant effect on the dolos 

 hydraulic stability, it is likely that they will not significantly affect the 

 design stress distribution that is based solely on the combination of static 

 and pulsating responses because the pulsating response is small compared to 

 the static response. Therefore, exclusion of these variables is reasonable. 

 Impact response 



61. Wave -induced impact. The impact stress is a function of the armor 

 unit hydrodynamic stability. There will be no impacts below the stability 

 threshold, but the impact stress above this threshold can be very high. 

 Preliminary tests have shown the design impact stresses to be on the order of 

 twice the combined static and pulsating stress for rocking in place. Because 

 no impacts were observed in the Crescent City prototype dolos data, the design 

 impact stress could not be determined for this initial design procedure. But 

 because the prototype dolos static stresses approached the critical material 

 strength, armor unit impact loads will not be allowed in the large dolos 

 designs. The design procedure is configured such that impact response EPFs 

 can be easily added in the future as they become available. 



62. Construction-caused impact. For the reasons stated above, 

 construction- caused impacts during dolos transport and placement must be 

 minimized. Dolos placement from floating barge-mounted cranes should there- 

 fore be avoided. 



Combined response 



63. Given two independent PDFs , f x (x) and f y (y) , the joint PDF can 

 be written using the convolution integral as 



f z = fj x (x)f y (z-x)dx (2D 



31 



