present random boundary conditions and highly varying drag profiles (Fig- 

 ure 3). Finally, the CAUs are generally unreinforced and because of their 

 deep sections and irregular shape, the stress -strain behavior of the concrete 

 is difficult to predict. Therefore, the design methods for any one CAU shape 

 must be unlike any other coastal or land-based method. 



Figure 3. 42 -ton dolosse at Crescent City, CA 

 CAU design unlike any other 



15. Until recently, no general CAU structural engineering design tools 

 were available. CAU design has been limited to determining the hydrodynamic 

 stability using empirical formulae like the formulae developed by Hudson 

 (1958) and more recently by van der Meer and Pilarczyk (1987) . The hydro- 

 dynamic stability design formulae generally assume that the critical design 

 condition occurs when several armor units are displaced from their equilibrium 

 positions, exposing the underlayer to direct wave action. The hydrodyna- 

 mically stable weight determined from an empirical formula is typically 

 verified in a physical model. 



16. In a conventional hydrodynamic stability model study, the strength 

 of the armor units is not scaled. The units are made of grout or polyester 

 materials, which produce model strengths several orders of magnitude greater 

 than scale. Thus, traditional design methods assume that the armor units will 

 remain structurally intact. But experience has shown that a breakwater might 



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