Trivariate joint probability model of typhoon-induced wind, wave and their time lag based on the numerical simulation of historical typhoons

Typhoon-induced wind and wave can interrupt the operation and even threaten the safety of moving vehicles and bridges. However, the typhoon-induced maximum wind speed and maximum wave height are not coincident in time. Hence, it is a critical issue to include the time lag in the hazard model of wind and wave conditions for bridges. This paper adopts the concept of the pair-copula decomposed model to develop a trivariate joint probability model of typhoon-induced maximum wind speed, maximum wave height and their time lag. Pingtan Strait, where a sea-crossing bridge is being built, is taken as the example site. Considering the long-term measured wind and wave conditions under typhoons are not available, 58 tropical cyclones from 1990 to 2018 that influenced the example site are selected. The typhoon-induced maximum wind speed, wave height and their time lag at the example site are simulated using the validated SWAN + ADCIRC coupled numerical model. The trivariate joint probability modeling of wind, wave and time lag was carried out based on the simulated data. The trivariate environmental surfaces with the 50-year and 100-year return periods were finally obtained by the inverse first-order reliability method. The results show that more than 50% of typhoons have the maximum wind lagged behind the maximum wave at the example site. The higher typhoon-induced maximum wind speed and wave height tend to occur simultaneously. Two-parameter Weibull distribution is suitable to fit the distribution of the maximum wind speed and wave height, and the GEV distribution is ideal for the distribution of time lag. According to the trivariate environmental surface, neglecting the time lag might slightly overestimate the demand of the wind and wave loads. This study is of particular interest to the researchers and engineers in developing the metocean conditions.