Dynamic analyses of offshore triceratops in ultra-deep waters under wind, wave, and current

Abstract

Compliant offshore platforms are sensitive to aerodynamic loads. Triceratops is one of the new generation compliant platforms consisting of a deck, which is connected to buoyant legs through ball joints. Ball joints partially isolate the deck from buoyant legs by transforming translational motion and restricting the rotational motion. Buoyant legs are connected to the seabed using taut-moored tethers. This study is carried out to assess the dynamic response of triceratops under the wind, wave and current loads at a water depth of 2400 m in different sea states. Numerical analysis is carried out using ANSYS AQWA under moderate, high and very high sea states. Results of studies show that aerodynamic load resonates response of deck in different degrees of freedom under moderate and high sea states. Pitch response of the deck is insignificant, verifying the satisfactory design of the conceived geometry. Statistical analyses show that the response increases with the increase in wave height and wind speed, but lesser than a surge in all sea states. Presence of current induces a shift in the mean position of surge response, and the platform oscillates at this new mean position; this shift increases with an increase in the sea states. Pitch response is significantly reduced under the combined wind, wave and current loads.