Combination Criteria of Joint Extreme Significant Wave Height and Wind Speed in Weizhoudao Offshore Area

With the data of annual maximum wave heights and their corresponding wind speeds acquired at Weizhoudao Observation Station in China from 1961 to 1989 as a statistical sample, the joint probabilities of extreme wave heights and wind speeds at the station are estimated by using the following distribution models: (1) the bi-variable Pearson-III distribution, (2) the conditional distribution, and (3) the independent distribution. To examine the dependence of design load criteria on the assignment of distribution model, design base shears of a jacket platform are computed by assigning one of the three models, respectively. It is found that the 100yrs base shear resulting from the model (1) is less by 7% than that resulting from the model (2), and is less by 18% than that resulting from the model (3). This suggests that the design load criteria could be reasonably reduced by considering the correlation between environmental conditions, so as to reduce the engineering investment of marine structures.