Non-Gaussian response of offshore platforms: dynamic.

A hybrid method, consisting of spectral and probabilistic analysis techniques, is proposed to evaluate the dynamic response characteristics of offshore platforms considering nonlinear wave kinematics and free surface fluctuation effects. The effect of nonlinear wave kinematics and intermittent loading is that the wave loading is non Gaussian. The response of platforms to such non Gaussian loading will be non Gaussian. A combination of spectral and probabilistic analyses is developed to estimate the response up to the fourth moment. The probability distribution of the response is estimated as a mixture of Gaussian distribution and shifted exponential distribution. With the help of an example, it is shown that the free surface fluctuations have a significant effect on the response. The skewness and kurtosis are shown to increase with an increase in significant wave height. The probability distribution is shown to deviate from the normally assumed Gaussian distribution, particularly at the tails commonly found in full scale measurements.