Comparison of Extreme Responses From Wheeler and Vertical Stretching Methods

Linear random wave theory (LRWT) is frequently used to simulate water particle kinematics at different nodes of an offshore structure from a reference surface elevation record. However, it is well known that LRWT leads to water particle kinematics with exaggerated high-frequency components in the vicinity of mean water level (MWL). To avoid this problem, empirical techniques such as Wheeler and vertical stretching methods are frequently used to provide a more realistic representation of the wave kinematics in the near surface zone. In this paper, the Monte Carlo time simulation technique is used to investigate the effect of these two different methods of simulating water particle kinematics on the probability distribution of extreme responses. It is shown that the difference could be significant leading to uncertainty as to which method should be used.