On the Prediction of Extreme Wave Crest Heights

1. INTRODUCTION An important parameter regarding structural safety is the height from the still water level (accounting for tide and storm surge) to the lowest deck level of the platform. Standard practise, at least for structures at the Norwegian Continental Shelf, is to require that this height is larger than the wave crest height occurring with an annual probability of occurrence of 10-4 after accounting properly for the increase in crest height due to wave-structure interaction. For floating structures this requirement may be rather difficult (or, rather, very costly) to meet and for such cases the requirement is to design the structure such that it can take the impact forces caused by these events with merely local damage, i.e. the impact event is not to escalate into a catastrophic failure. For floating structures it is of course the relative wave motion that is of concern, but the methodology used herein for the undis turbed wave crests may also be applied for the relative wave motion.