Probability Distribution of Wave Force

In many design problems the sea state is specified as part of the design criteria. For offshore structures it is important to know the maximum probable wave height and the maximum probable wave force which might be experienced during the life expectancy of the structure, for example the 50 yr or 100 yr wave height and period and the 50 yr or 100 yr wave force. Based on previous analysis of wave and wave force measurements, practically no correlation was found between the measured apparent wave height and apparent wave force. Several authors have proposed statistical distribution of drag and mass coefficients, with recommendations for use in design. The statistical distribution of the calculated drag (or mass) coefficients has no relationship to the statistical distribution of the measured wave drag forces (or inertial forces). Borgman (1964) has considered the statistical distribution of wave forces. Methods are presented for predicting the probability distributions of peak wave drag and inertial forces, and a method is proposed which might be used to predict the most probable maximum wave force once the sea state is specified. It is found that there is a good correlation between the probability distributions of wave heights and the probability distributions of peak drag forces. For example, if the most probable maximum wave height is given from a statistical distribution of wave height, then it is possible to predict the most probable maximum drag (or inertial) force, and the most probable maximum force (combined drag and inertial force).