Coastal distributions of design environmental loads in typhoon-affected sea area based on the trivariate joint distribution and environmental contour method

Southeast China's coastal areas usually suffer from typhoons, accompanied by extreme wind, waves, and currents, which threaten offshore structural safety. To mitigate the risk of failure, herein, an integrated assessment framework is developed to estimate typhoon-induced environmental loads along the coast. An environmental database of 30-year is obtained from verified numerical simulations. A methodology for extracting typhoon-induced extreme values is proposed to determine the extreme environmental variables and trivariate joint distributions are constructed. The structure of vine copula ensures that the marginal, bivariate, and trivariate distributions can match their respective optimal model, and provide appropriate correlations for three-dimensional environmental contours (ECs). Thus, physical information from the metoceanic environment is transferred to the probabilistic space and structural response. The results reveal that the EC profiles exhibit a pronounced layered distribution along the wind axis, which indicates the dominant role of wind loads in structural safety. The spatial distributions of 137 sites along the coastal areas are analyzed to reveal the inherent relationships between typhoon propagation, environmental loads, topographical change, and structural response. The central part of the coast is prone to failure owing to undiminished typhoon intensity.