A New Method of Moments for Reducing the Sampling Variability of Estimated Values of Probability Distribution Parameters

Offshore structures are exposed to random wave loading in the ocean environment and hence the probability distribution of their response to wave loading is the minimum requirement for probabilistic analysis of these structures. Even if the structural system can be assumed to be linear, due to nonlinearity of the wave loading mechanism and also due to the intermittency of wave loading on members in the splash zone, the response is often non-Gaussian. The method of moments is frequently used to determine the parameters of an adopted probability model from a simulated or measured record of response. However, when higher order moments (e.g. 3^rd or 4^th order moments) are required for estimation of the distribution parameters, the estimated values show considerable scatter due to high sampling variability. In this paper, a more efficient form of the method of moments is introduced, which will lead to more accurate estimates of the distribution parameters by reducing their sampling variability.