Towing of Proto-Type Offshore Structure

Abstract

The full-scale experiment has been carried out using the proto-type offshore floating platform of column-footing type (L×B×d=34m×24m×5.5m) named "POSEIDON" at 3km off of Yura port, Tsuruoka city, Yamagata prefecture for 4 years from 1986 to 1990. The experimental structure was constructed at Naruto city, Tokushima prefecture and was towed about 900 nautical miles all the way to the experimental cite. The towline tension has been measured during towing. On the design stage, the model experiment has been carried out in order to estimate the towing resistance and mameueverability. On the other hand, the measurement for the towline tension and the motion of the floating structure has been made during towing to Sakata port about 20 nautical miles north of the experimental site for scrapping the structure after finishing the experiment. The estimation for the average towline tension from the model test agrees well with the obtained results. As for the fluctuating towline tension, there exists the high frequency component wthich coincides with the wave frequency and the low frequency component. The average towline tension and the fluctuating towline tension are mainly discussed in this paper.