Experimental Investigation of Dynamic Responses for Semi-submersible Platform: Short Crested Waves vs. Long Crested Waves

In the real sea conditions only short crested
waves are found. The short crested waves are defined as linear
summation of different long crested waves propagated in
different directions. The wave forces generated would be
randomly varying in magnitude and direction. The statistics of
short crested waves are adopted for the design of offshore
structures to obtain the optimum design of the structures for
cost and time effectiveness. However, the researches focused
on short crested waves are limited especially on deepwater
structures. In this study, the dynamic responses of semisubmersible
platform were investigated experimentally. The
experimental tests were conducted in the wave tank of
Offshore Laboratory, Universiti Teknologi PETRONAS. For
the tests, a standard cosine spreading law was added to the
Pierson-Moskowitz (P-M) and JONSWAP spectrum to
generate the multi-directional waves. The results in term of
motion responses for the floater subjected to the bi-directional
and multi-directional short crested waves are compared with
that due to long crested waves.