Effects of random wave surface fluctuation on response of offshore structures

This paper seeks to determine the effects of free surface fluctuation on the response of an offshore structure in a random wave field. The structure is idealized as a massless uniform vertical column fixed at the sea bed carrying a concentrated mass at its top. The waves are linear, Gaussian, stationary and longcrested with narrow-band spectrum. The wave forces are computed using the Morison equation. It is shown that free surface fluctuation reduces structural response, more so in shallower than in deeper water, especially when the sea is high and when the structure is susceptible to dynamic action.