Experimental and Analytical Investigation for the Responses of Semi-Submersible Platform

This paper presents the results of model tests of an offshore semisubmersible
platform subjected to regular sea waves that was
conducted in the wave tank of the offshore engineering laboratory at
Universiti Teknologi PETRONAS. The measured responses were
compared with the numerical results obtained by using time domain
analysis and linear wave diffraction analysis. The semi-submersible
platform prototype was modeled as a rigid body with three degrees of
freedom restrained by mooring lines. In the time domain analysis,
Linear Airy wave theory and Morison modified equation were used
for calculating the wave forces on the structure. The mass, damping
and stiffness matrices were evaluated at every time step and the
equations of motion were formulated for the platform dynamic
equilibrium. The equations were solved using Newmark Beta time domain dynamic analysis method. The results were obtained as Response Amplitude Operators (RAO) in surge, heave and pitch. Then the RAOs were obtained using software by linear wave diffraction analysis. The wave tank tests responses were compared with the analytical responses and the approaches were validated the applicability on the structures with large hulls e.g. the semisubmersible
platforms.