Abstract

In this study, the wave run-up over a simplified semi-submergible platform with two columns in regular wave is predicted numerically using a three-dimensional particle method in order to investigate the wave run-up and wave impact on the columns of the platform. A series of fully-nonlinear regular waves are generated by a flap-type wave- maker in a numerical wave tank, and the reflected waves from the opposite side of wave-maker are induced to be intentionally dissipated in the beach region including wave absorbers. The results of the present simulation for time-series of wave run-up and impact pressure acting on the columns of the platform are compared with those of the grid- based simulations and experiments performed by MARIN.

Introduction

The area for developing fossil fuel has gradually expanded to the deep sea because demands for fossil fuel from developing countries have been gradually increased. There are many types of offshore structures operated in deep sea, such as semi-submersible, spar and ship-shaped vessels. Especially, semi-submersible offshore structure has been usually operated in the deep ocean of harsh environment because the structure represents good performance in heave motion. However, these offshore structures have been continuously subjected to severe wave impact loads caused by environmental conditions due to long operating time in a local place. In addition, there were some reports on failure of semi-submersible structure operated in offshore, such like Alexander Kielland in 1980(ALK, 1981; Moan, 1981; Moan and Holland, 1981), Ocean Ranger in 1982 (OR, 1984), P-36 in 2001 (P-36, 2003). Therefore it is of significant to predict accurately wave impact loads on semi-submersible structure for safe and economical design of the structure.

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