Impact of copula model selection on reliability-based design optimization of a rubble mound breakwater

Reliability-based design optimization (RBDO) is one of the most well-known methods to deal with uncertainties in the design methods. There are still challenges with the application of RBDO in the design of coastal structures, such as data adequacy, computational cost, and the correlation between environmental variables. The current study aims at addressing these items and bringing insights into the correlated design. In this regard, a step has been taken forward, and the RBDO of a rubble mound breakwater has been performed by considering the cor-relation among significant wave height, wave period and water level. Four different copulas are considered: Independence, the Gaussian, the Drawable Vine dependence, and the Gumbel. The expected lifetime costs for the independence, the Gaussian, and the Gumbel dependence cases are 9.32%, 5.70%, and 3.12% lower than that of the D-vine case. The results indicate that considering a suitable vine structure, the optimal solutions of the In-dependence, the Gaussian, and the Gumbel copulas are not reliable. While without considering this dependence structure, the obtained designs have met the probabilistic criterion. This is a novel and crucial outcome and highlights the significance of the proper selection of dependence structure on the reliable design of marine structures.