POLOS DESIGN PROCEDURE BASED ON 

 CRESCENT CITY PROTOTYPE DATA 



PART I: INTRODUCTION 



Purpose 



1. Concrete armor unit (CAU) structural failure has been a primary 

 factor in the breakdown of many coastal rubble structures. Rational CAU 

 structural design has been slow to develop due to the complex and random 

 nature of the armor layer loads and the resulting response. CAU structural 

 design is currently based on engineering judgement with little or no rigorous 

 analysis. The CAU structural designer must have design methods that combine 

 both deterministic and probabilistic techniques in order to develop both safe 

 and cost-effective designs. The purpose of this report is to propose design 

 methodologies for the safe design of dolosse and to provide a template for 

 general CAU design. 



Armor Units. Concrete Armor, and Dolosse 



Engineering characteristics of armor 



2. Armor units are used to protect coastal rubble-mound structures 

 from erosion by the sea. Many types of armor unit shapes are available and 

 each has its own engineering performance characteristics. The various cate- 

 gories of armor units include stone, concrete blocks, concrete mats, and 

 slender complex- shaped concrete units. The default armor unit is stone for 

 both economic and aesthetic reasons. CAUs are used when the costs associated 

 with quarrying, transporting, and placing stone armor large enough to be 

 hydrodynamically stable exceed those of CAUs. In high wave energy environ- 

 ments, such as the U.S. west coast and Pacific Ocean islands, concrete armor 

 is often a design alternative because of the high costs of large stones. In 

 lesser wave energy locations such as the U.S. east coast and along the Gulf of 

 Mexico coastline, concrete armor will be increasingly important as stone armor 

 availability decreases. 



3. CAUs, as shown in Figure 1, come in a variety of shapes. While 

 many different CAU shapes have been developed, CAU shapes fall somewhere 



