Experimental investigation on dynamic responses of spar platforms subjected to multi-directional waves

In the real sea, only multidirectional waves or short crested waves are found. 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. In this paper, an experimental investigation on dynamic responses of spar platform subjected to multi-directional waves is presented. The model tests were performed in the wave tank of Offshore Engineering Laboratory of Universiti Teknologi PETRONAS. In the tests, a standard cosine spreading law was added to the Pierson-Moskowitz (P-M) and JONSWAP spectra to generate the multi-directional waves. The response data were collected and processed to obtain the dynamic responses of the spar model in terms of RAOs. The responses in 3 degree-of-freedom were presented and it was found that short crested waves, namely the multi-directional waves induce smaller responses compared to the long crested waves.