difficult. The primary technical problem with the method is that there is no 

 way to separate the response due to the different forcing functions. The 

 unit-to-unit impact loads scale differently than do the wave and self -weight 

 loads. To scale the entire response requires a material that is too difficult 

 to work with in the laboratory. 

 Conventional structural analysis methods 



19. Seawall design is similar to conventional land-based structural 

 design where conventional structural analysis techniques are used with lab and 

 field-measured loadings to determine the internal stresses and overturning 

 moments. This is the classical approach to structural analysis where the 

 loads are determined and then applied to the structure, and analytical and 

 numerical methods are used to solve for the structural response. In conven- 

 tional structural design, load factors are often applied to the loads to 

 account for understrength or overload. The structural response to these 

 modified loads is commonly analyzed using deterministic matrix methods such as 

 a stiffness formulation or, for continuous media, finite element methods 

 (FEM) . The individual members are sized to resist the maximum stresses. 



20. But conventional structural analysis cannot be employed for armor 

 layer analysis because the loadings are not yet known. Many laboratory tests 

 with the appropriate instrumentation would be required to quantify the loads 

 on a given armor unit for any given set of design parameters. Even then, 

 because the boundary condition scenarios are so varied and the concrete be- 

 havior difficult to quantify, accurate stress quantification by a design 

 engineer would be technically very difficult and not economically feasible. 

 Stochastic stress design methods 



21. The design method discussed in this report follows basic 

 reliability techniques with determination of the armor layer design stress 

 from a design probability distribution of maximum dolos stresses. Using this 

 stochastically based design method, the designer need not be concerned with 

 the loads on, or the stresses within, each dolos. This design procedure 

 utilizes deterministic modifications to prototype dolos static and pulsating 

 stress distribution statistical moments to compute separate design 

 distributions. Handling the static and pulsating stress distributions 

 separately allows independent modification and scaling of the distributions. 

 The individual distributions are computed and combined in the microcomputer- 

 based program called CAUDAID (Concrete Armor Unit Design Aid) (Appendix A) . 



13 



