This paper addresses the problem of estimating the waves run up for a large semi-submersible production platform. Significant run-up evaluations on its squared-section columns were observed for the waves in operating design displacement. Some seed numbers generated JONSWAP waves in tank were used, and are generally regarded as a pure randomness in nature. Some identical sequences of relatively waves run up were found apart from one another for different seeds. This finding supports the recurrence of waves run up for the large semisubmersible platform.


The deep water scenario of oil and gas exploitation in Malaysia is one of the main factors that are inspiring the government and offshore company to develop a new generation of 58,748 tones semisubmersibles, characterized by having large displacement hulls. These platforms are stabilized by a 4 rectangular columns arrangement and its position is maintained by 12 chain catenary anchor legs. Given the impact that this level may have on the system, the high accuracy prediction methods have been conducted, although they are not adequately established. There are various reasons that make the implementation of numerical methods even harder and they are related to the complexity of the hydrodynamic problem. Once the design criteria for air gap definition are associated to extreme events, problems such as the non-linearity of incoming and scattered waves play an important role. On semi submersible platforms, one of the critical lower-deck areas are those in centre line and surrounding the columns, frequently subjected to the wave run-up phenomenon. According to Eatock Taylor and Sincock, hydrodynamic interaction effects between large columns can cause substantial increases in local wave height. They analyzed this phenomenon of wave upwelling theoretically using a high order hybrid element technique. It was concluded that wave upwelling effects are highly significant and should be considered in design.

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