A Reliability Design Method of Caisson Breakwaters with Optimal Wave Heights

AbstractThe paper presents an improved version of the deformation-based reliability design method by means of expected sliding distance proposed by Shimosako and Takahashi (1998 and 1999). The process of economic optimization is added, and the concept of the optimal return period for selection of design wave heights is introduced with a sample diagram for the optimal return period for three values of service lifetime. It proposes a new tolerable limit of expected sliding distance of 0.10 m instead of the value of 0.3 m adopted by Shimosako and Takahashi. The ratio of water depth to the significant wave height is demonstrated to govern the reliability design of caisson breakwaters, because of random wave breaking effects. In shallow water, a breakwater can be designed with the cross section smaller than that by the conventional design, but a larger cross section is needed in deeper water. Discussions are made on the comparison between the partial safety factor systems proposed by European groups and on the future problems to be solved for further refinements of the deformation-based design method.