Fatigue Assessment of Offshore Triceratops Restraining System Under Hurricane-driven Metocean Conditions

Chandrasekaran, S.; Shah, Bharat; Chauhan, Yogesh J.

doi:10.1007/s13296-022-00689-w

Cited by 6 publications

(2 citation statements)

References 28 publications

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“…The offshore platform's buoyancy is very high compared to the platform's self-weight, and the excess buoyancy is taken care of by pretension tethers. The fatigue damage studies are very much useful to analyze the service life of the compliant taut moored platforms and floating structures [8][9][10][11][12][13][14]. The stability IOP Publishing doi:10.1088/1757-899X/1288/1/012032 2 of positively buoyant structures is more tactful to tethers, so the postulated failure is a fundamental analysis scenario that must be considered during the compliant taut moored platforms design process [15,16].…”

Section: Introductionmentioning

confidence: 99%

Dynamic response of offshore triceratops under regular waves with tether postulated failure

Chandrasekaran¹,

Rao

2023

IOP Conf. Ser.: Mater. Sci. Eng.

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Triceratops are innovative offshore platforms that consist of a deck, three buoyant legs, and ball joints. Their deck is supported by buoyant legs, which, in turn, are restrained on the sea bed using taut-moored tubular tethers. Ball joints partially isolate the deck from the buoyant legs by restraining the transfer of rotations from the legs to the deck. Triceratops platforms exhibit a monolithic structural action in the vertical plane and a hybrid dynamic behavior resembling tension leg platforms and spar buoys. The present study investigates their dynamic response in regular waves. Response amplitude operators (RAOs) are estimated for intact and postulated failure conditions of the tethers. Based on detailed numerical investigations, it is seen that the pitch response of the deck increases significantly under the postulated failure of tethers, which are otherwise absent due to the presence of ball joints. Marginal change in surge response, even under tether failure, confirms the suitability of triceratops for ultra-deepwater installations. The fatigue life of tethers before and after postulated failure conditions is compared using the S-N curve approach and noticed that the adjacent tethers’ fatigue life reduces significantly under postulated failure conditions of tethers.

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Section: Introductionmentioning

confidence: 99%

Dynamic response of offshore triceratops under regular waves with tether postulated failure

Chandrasekaran¹,

Rao

2023

IOP Conf. Ser.: Mater. Sci. Eng.

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“…Support systems of offshore wind turbines are chosen from a wide range, namely TLPs, trifloaters, shallow-draft barge, and fixed platforms (Chandrasekaran et al, 2023a;2023b;Hendersen & Patel, 2003;Srinivasan, 2016;Skare et al, 2007;Wayman et al, 2006;Zambrano et al, 2006;. Linear frequency domain analysis is used for systems in which wind turbine characteristics are included by supplementing the mass matrix.…”

Section: Introductionmentioning

confidence: 99%

Dynamic analysis of offshore triceratops supporting wind turbine: Preliminary studies

Chandrasekaran,

Chinu

2023

Marit. Technol. Res.

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Offshore triceratops, the recent innovation in deep water compliant platforms, is primarily designed to withstand lateral forces through its geometric shape. The uniqueness of the platform is the presence of the ball joints between the legs and deck, which partially restrain the transfer of rotations from the legs to the deck and vice-versa. However, displacements such as surge, sway, and heave motions are transferred, ensuring a rigid connection between the legs and the deck. Efficient operations of offshore wind turbines are more dependent on the support systems on which they are mounted. Increased stability and reduction in stress concentration in rigid connections are desirable. Nonlinear dynamic response analysis is carried out in FAST by coupling the frequency response of the platform obtained in ANSYS AQWA with that of the HydroDyn module of FAST. The current study investigates a fully coupled three-dimensional hydro-aerodynamic model of triceratops mounted with a horizontal axis wind turbine. Unsteady Blade Element Momentum theory (BEM) is used to estimate the aerodynamic loads, which encompasses the effect of wind shear using a power law and spatially coherent turbulence. In contrast, Morison equations are used to estimate the hydrodynamic loads on the platform. After the preliminary proportioning of the platform, Response Amplitude Operator (RAO) plots are drawn to illustrate the partial motion transfer between the deck and the buoyant legs. Based on the preliminary studies, it is seen that the environmental loads do not impose instability, reinforcing the dynamic stability of the platform. Frequency responses for operating and parked conditions illustrate the coupling between the degrees of freedom and the influence of the rotor motion of the wind turbine on the platform deck. Tether tension variation is assessed in all three legs for the operational sea states to check the safety standards for a compliant system to avoid tether pull-out. The presented study is prima facie to encourage the suitability of triceratops as floaters to support the wind turbine under moderate sea states. Highlights This study is focused on new-generation offshore triceratops as support system for wind turbine Prelimiary dynamic anlaysis of coupled action of the supprting system and wind turbine are presented Use of ball joints help partial isolation of the deck and restrain transfer of moment from the turbine shaft to the supporting system, which is a novelty Infleunce of rotor motion of the triceratops is illustarted to highlight the advantage of complinacy of trirceratops This study disucsses only the performance assessment and not the design perspectives

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Steel Coped Beam with Functionally Graded Material for Offshore Topside: Numerical Investigations

Chandrasekaran,

Thennavan

2024

Int J Steel Struct

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Fatigue Assessment of Offshore Triceratops Restraining System Under Hurricane-driven Metocean Conditions

Cited by 6 publications

References 28 publications

Dynamic response of offshore triceratops under regular waves with tether postulated failure

Dynamic response of offshore triceratops under regular waves with tether postulated failure

Dynamic analysis of offshore triceratops supporting wind turbine: Preliminary studies

Steel Coped Beam with Functionally Graded Material for Offshore Topside: Numerical Investigations

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