Implications of Tendon Modeling on Nonlinear Response of TLP

Mekha, Basim; Johnson, Chloe; Roësset, José M.

doi:10.1061/(asce)0733-9445(1996)122:2(142)

Cited by 13 publications

(13 citation statements)

References 6 publications

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“…Inclusion of the tendon force does not signi®cantly affect the amplitude of the surge response as supported by the literature [6,12]. However, researchers have also shown that at greater tendon lengths, the importance of including a more sophisticated tendon model increases [6,9].…”

Section: Casementioning

confidence: 74%

“…Due to the length of a tendon compared to its diameter, modeling the tendon as a cable may be a reasonable assumption. However, in order to maintain generality and retain higher-order effects, a beam model is used which retains the tendon's stiffness [10,12,22].…”

Section: Derivation Of the Lagrangianmentioning

confidence: 99%

“…Mekha et al [12] created three different tendon models. The ®rst was as a massless spring to provide a constant lateral stiffness with TLP setdown disregarded.…”

Section: Introductionmentioning

confidence: 99%

See 2 more Smart Citations

Response of a tension leg platform to stochastic wave forces

Adrezin

Benaroya

1999

Probabilistic Engineering Mechanics

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Section: Casementioning

confidence: 74%

Section: Derivation Of the Lagrangianmentioning

confidence: 99%

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Response of a tension leg platform to stochastic wave forces

Adrezin

Benaroya

1999

Probabilistic Engineering Mechanics

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“…This was determined to be the governing failure criterion. Mekha et al (1996) [9] created three different tendon models. The first was as a massless spring to provide a constant lateral stiffness with TLP setdown neglected.…”

Section: Brief Reviewmentioning

confidence: 99%

Stochastic nonlinear response of coupled tendon-rigid body system

Adrezin

Benaroya

1997

38th Structures, Structural Dynamics, and Materials Conference

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A coupled tendon-rigid body model which may be used for the study of offshore or space structures is presented. A set of fully non-linear equations of motion for a single-tendon tension leg platform are developed. The response is analyzed for random wave and steady current loading. Motion is assumed to be planar and the equations of motion for the elastic tendon and the rigid hull are coupled. The response is determined numerically in the time domain by implementing a finite difference scheme. The responses for a model with a 470 m long tendon and a 50 m long hull exhibit both transient and steady state behavior. When waves forces alone are applied, the system oscillates about its vertical position. A combined load of waves and current produce an oscillation about an offset position, as has been shown in the literature. The analytical model presented in this paper would be useful to the designers of TLPs in determining the overall dynamic response characteristics. PROBLEM STATEMENTIn this paper, a set of fully non-linear equations of motion for a single-tendon tension leg platform are developed. Many of the simplifying assumptions used by prior researchers have been eliminated. The response is analyzed for random wave and current loading. Motion is assumed to be planar and the equations of motion for the tendon and the hull are coupled. The response is determined numerically in the time domain by implementing a finite difference scheme.Two assumptions were made in the modelling of the tendon: the tendon length is much greater than its diameter and the tendon is inextensible. The former is clear from the physical dimensions of a tendon, and the latter can be shown by comparing the first natural frequency of a beam for transverse vibration with that for longitudinal vibration. The ratio of longitudinal to transverse frequency is of the order of the length to its diameter which was assumed large.The tendon's bending stiffness, internal tension, and linear and rotational inertia are included resulting in a highly non-linear fourth-order partial differential equation of motion. As the hull undergoes surge motion, the set-down effect results in a greater submerged hull volume thereby increasing the tension in the tendon. The forces on the hull also enter the equations for the boundary conditions at the top of the tendon.The hull is treated as a rigid body and is represented by a hollow cylinder where its top must always remain above the water surface and its bottom below. Its center of gravity is located at the center of hull's volume and the center of buoyancy is a function of its submerged volume and orientation. Linear wave theory is applied and the waterlevel is assumed constant and horizontal across the hull's column at a given instance of time. This coupled tendon-rigid body model may be used for the study of offshore or space structures. BRIEF REVIEWOf the classes of offshore structures, the tension leg platform (TLP) is particularly well suited for deepwater operation. Unlike fixed structures, its cost does not...

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“…As suggested by the works surveyed [2,8,14], in certain circumstances, it is reasonable to replace the FEA cable with a linear spring equivalent. The idea behind the substitution is to increase simulation efficiency and speed, while maintaining accuracy.…”

Section: Introductionmentioning

confidence: 99%

Preliminary Assessment of the Importance of Platform–Tendon Coupling in a Tension Leg Platform

Masciola¹,

Nahon

Driscoll

2013

Journal of Offshore Mechanics and Arctic Engineering

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This paper presents performance metrics that can be used to evaluate the response sensitivity of a tension leg platform (TLP) to its tendons. An uncoupled TLP model ignores the intrinsic dynamics and environmental loads on the cables by treating each tendon as an ideal massless spring. A coupled TLP system, in contrast, considers the effects of distributed mass and drag along the tendon. Under certain operating conditions, an uncoupled dynamics model can produce results comparable to its coupled counterpart. This paper defines the conditions under which it is acceptable to model a TLP tendon as a linear spring, as opposed to one that considers the cable dynamics. The analysis is performed in the frequency domain and, for generality, the results are nondimensionalized. The findings indicate that a more elaborate set of conditions than the platform–to–cable mass ratio must be satisfied for the two models to provide similar results. To conclude this study, two simulations are performed and compared against the performance metrics derived in this paper.

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Implications of Tendon Modeling on Nonlinear Response of TLP

Cited by 13 publications

References 6 publications

Response of a tension leg platform to stochastic wave forces

Response of a tension leg platform to stochastic wave forces

Stochastic nonlinear response of coupled tendon-rigid body system

Preliminary Assessment of the Importance of Platform–Tendon Coupling in a Tension Leg Platform

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