Experimental and Analytical Investigation of Classic Spar Responses

Abstract - This paper presents the results of model tests
of an offshore classic spar 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 Morison
equation and linear diffraction method. The classic spar
was modeled as a rigid body with three degrees of
freedom restrained by mooring lines. Linear Airy wave
theory and Morison modified equation were used for
calculating the wave forces on the structure in the first
case. 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 transfer functions in surge, heave and pitch.
In the second case, the transfer functions were obtained
using software based on linear diffraction method. The
experimental responses were compared with the
analytical responses and found in good agreement.