Efficient estimation of the skewness of the response of a wave-excited oscillator

The Multiple Timescale Spectral Analysis is a framework relying on the existence of well-separated timescales in the dynamic response of structures to generalize for higher-order statistics the famous background/resonant decomposition, widely applied by the wind engineer- ing community to compute the variance of the response of SDOF structures or of each modal response of MDOF structures. This fast spectral analysis method mainly concerns the statistics of the response of onshore structures subjected to a buffeting wind loading whose characteristic frequency is typically lower than the natural frequencies of the structures concerned. By con- trast, when dealing with wave-loaded floating offshore structures, the roles of the slow and fast timescales are likely to be interchanged and the method is extended further in this paper to com- pute rapidly the variances and the skewnesses of modal responses of such structures responding in the inertial regime as well, since these statistics are necessary to consider the influence of the non-Gaussianity of the loading.