Prediction of Design Wave Heights : A Case Study for the Forties Field at the North Sea

Offshore structures are exposed to random waves in the ocean environment and hence random waves must be used for their design. However, it is common practice and also much simpler to use regular design waves for analysis of jacket structures which do not respond dynamically to wave loading. This is usually the case for structures which are in water depths less than 120 meters. Design waves are usually described in terms of a given return period. For example, the American Petroleum Institute recommends the structure to be strong enough to withstand the 100-year wave at the site of the structure. The main objective of this project is to calculate the 100-year design wave for the Forties field in the North Sea. There are two different procedures for calculating the 100-year waveheight. The first procedure is based on the long-term probability distribution of individual waveheights in a particular site. The second procedure is based on the long-term probability distribution of the extreme waveheight during a fixed period of time. The second procedure is more accurate and hence will be used for derivation of the 100-year waveheight in this study.