Dynamic analyses of stiffened triceratops under regular waves: experimental investigations

Abstract

ABSTRACTGeometric forms of offshore complaint structures deployed for ultra-deep waters are modified significantly to conform to higher degree of compliancy. One such recent innovation is the stiffened triceratops, which is discussed in this study. The platform comprises of three buoyant leg structures (BLS), supporting the deck. Each single buoyant leg unit is interconnected with a finite number of stiffeners to make it monolithic and thereby reducing the effect of encountered wave loads. However, BLS units are not interconnected so that their compliancy by design is not compromised. Ball joints are introduced between the buoyant legs and the deck to restrain transfer of rotation from the BLS units to the deck and vice versa. In this study, experimental investigations carried out on the scaled mode of stiffened triceratops to estimate its dynamic response characteristics under regular waves are discussed in detail. Results show that the translational and rotational motion of the deck in all active degrees-of-freedom decreased significantly due to the presence of ball joints while stiffening of BLS units increased the tether tension. It is also seen that the pitch response decreases significantly with the increase in wave period, while this effect is marginal on surge and heave responses.