Optimal Linearization of Morison‐Type Wave Loading

The linearization of Morison‐type wave loading is to replace $u\left|u\right|$ by cu, where u is a zero mean, stationary Gaussian random process and c is a constant. The coefficient c is traditionally determined by a use of the statistical least‐square error linearization; that is minimizing $E\left[\right(u\left|u\right|-\mathrm{cu}{)}^2]\text{.}$ In this study, the optimal linearization refers to a coefficient c, chosen in such a way that the statistics of structural response calculated from the linearized force will be identical to that calculated from the originally nonlinear force. To accomplish this, the optimal linearization must not only consider the ocean wave properties, but incorporate the structural properties. While most offshore structural engineers believe that the least‐square linearization may cause significantly nonconservative error only when the fundamental structural frequency is nearly three times the peak wave frequency, this study shows that worse errors may occur for other frequency ratios.