RESPONSE STATISTICS OF OCEAN STRUCTURES TO NONLINEAR HYDRODYNAMIC LOADING .2. NON-GAUSSIAN OCEAN WAVES

In this second part, the response statistics of ocean elastic systems to non-linear hydrodynamic loading represented by a non-Gaussian rando m process are considered. The non-Gaussian process is generated from a non-linear filter excited by a white noise process. The filter non-li nearity is represented by a gradient of a potential function where an exact closed form solution of the stationary probability density exist s. The filter non-linearity is selected such that its response probabi lity density function exhibits the skewness feature of ocean waves. In order to estimate the filter power spectrum, a joint probability dens ity function of the filter response co-ordinates at two different time s is derived, using an orthogonal expansion technique together with th e Fokker-Planck equation. This process yields a first order differenti al equation governing the time evolution of the filter response statis tics. This equation forms an infinite hierarchy of coupled equations w hich are solved up to rank 10. The power spectra of the filter are obt ained for different filter and excitation parameters. The response sta tistics of a linear elastic structure subjected to non-Gaussian non-li near hydrodynamic forces are determined using the stochastic averaging method and, alternatively, the orthogonal expansion method. (C) 1996 Academic Press Limited