ICE-INDUCED response of offshore triceratops

Abstract

Increase in drilling operations in the Arctic region intuits to examine the suitability of platforms under ice loads. This paper examines the dynamic response of triceratops under continuous ice crushing. Effect of ice loads on one and adjacent buoyant legs are examined under different ice velocity, crushing strength and ice thickness. Based on the numerical investigations carried out, it is seen that the response of deck in active degrees-of-freedom is nonlinear, showing higher response with the increase in ice crushing strength. Ice loads cause a shift in the mean response. Limit ice load acting on the buoyant legs increases with the increase in the ice thickness. With the increase in ice crushing strength, set-down increases along with the increase in the mean value of surge; mean and total yaw response also increases with the increase in the ice crushing strength. Increased deck response under ice loads is due to transfer of translational response from buoyant legs to deck by ball joints. However, pitch response of the deck is lesser than that of buoyant legs, verifying the restraint offered by ball joints to transfer rotation. It may be an added advantage of triceratops under ice-infested sea loads. Though this may not be the only sufficient requirement, certainly no transfer of rotational response from buoyant leg to the deck enables a comfortable working environment. From the analysis of triceratops under lock-in ice condition, it is found that the response of the deck and buoyant legs is bounded and the resonance build up is not seen in any degrees-of-freedom due to damping present in the structure, which is an additional advantage of a triceratops.