Aibel is developing an offshore power converter platform concept. Its foundation is gravity-based and consists of four columns interconnected by a ring-shaped pontoon at the seabed. The platform is intended for water depths in the order of 20 to 40m. In these waters, breaking waves typically cause large wave loads on the foundation that need to be accounted for in the design. The slamming loads, pressures and air gap at the platform were investigated with a combined approach of physical and numerical modeling. This paper summarizes the set-up, test program, measurement techniques, results and analysis of the physical model tests.

The tests showed that reflection and diffraction patterns caused a significant steepening of the waves between the columns, reducing the air gap and increasing the slamming frequency and magnitude on the downstream columns and underside of the deck. Excitation of resonant wave modes was identified for certain wave frequencies. Although the global wave loads were primarily governed by inertia, largest loads occurred under slamming impacts on the upstream columns, in phase with the inertial force.

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