Experimental investigation for the responses of semi-submersible platform subjected to bidirectional waves

It is rare to find unidirectional wave in the real seas and only multi-directional waves or short crested waves are found. The short crested waves are defined as linear summation of different long crested waves propagated to different directions. The wave forces generated would be randomly varying in magnitude and direction. Nowadays, designers tend to use the directional wave statistics for the design of offshore structures. The main reason is to obtain the optimum design of the structures for cost and time effectiveness. As a part of the research focused on the dynamic responses of the semi-submersible platform subjected to short crested waves, this paper presents the results of the experimental investigation for semi-submersible platform subjected to short crested bidirectional wave. The experiment was conducted in the wave tank of the offshore engineering laboratory at Universiti Teknologi PETRONAS. The model was subjected to 5 sets of bi-direction waves crossing angles of 40°, 45°, 55°, 90° and 120°. The direction of the wave propagating was found to affect the responses. Two typical trends of the responses were found for wave crossing angles of 40°, 90° and 120° along with 45° and 55° respectively. The optimum wave crossing angle 40° and 55° give the maximum responses.