On the estimation of design wave forces

The determination of wave-induced loads on ocean structures is a key aspect in the design of such structures. In the present study, five alternative approaches to estimating the load levels associated with a specified return period are described. The alternative approaches are based on different treatments of available wave data, rather than on new force formulations. The approaches include the estimation of a maximum wave height directly from the longterm distribution of significant wave heights (Method A); from the long-term distribution of individual wave heights (Method B); from the joint distribution of heights and periods (Method C); from a first order reliability method applied to estimating the maximum wave height (Method D); and from a first order reliability method applied to estimating the maximum wave force directly (Method E). These approaches to estimating the maximum wave force are carried out for small and large vertical circular cylinders. The analyses are also carried out to indicate the influence of wave period and the type of analytical distribution of significant wave height that is adopted. The results show that the most conventional approach, Method A, predicts relatively low values of the maximum wave force for both the slender and large cylinder. The estimation by Method C is closer to Method A. The force values by other methods are significantly higher for the large cylinder than the slender cylinder. The Type HI distribution for H s gives lower force values than Type I distribution. The force values are higher when T = 4.43 -Jns than T is constant. In general, the results indicate that For both slender and large cylinder, the estimation of wave force by the Methods B, D and E might be on the conservative side, while by the Methods A and C may be less conservative.Applied Science, Faculty ofCivil Engineering, Department ofGraduat