FEM modelling and automatic control for collision prevention of top tensioned risers

Rustad, Anne Marthine; Larsen, Carl M.; Sørensen, Asgeir J.

doi:10.1016/j.marstruc.2007.04.003

Cited by 36 publications

(15 citation statements)

References 19 publications

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“…9b, 10b and 11b it can be seen that realization of displacements of point E requires a characteristic force which is not larger than ±5 % of the tangential force. Special devices are necessary for technical realization of the optimal displacement (y E (t) or force T L; t ð Þ) Information about the method of realizing displacements at point E and about devices used can be found in papers dealing with "heave compensation systems" [26,27].…”

Section: Optimisationmentioning

confidence: 99%

Compensation of top horizontal displacements of a riser

et al. 2016

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The nonlinear dynamic problem of catenary risers is solved by means of the rigid finite element method. The method enables us to model slender systems such as lines, cables and risers undergoing large base motions. The formulation allows elimination of large values of stiffness coefficients: shear, longitudinal and torsional (dependent on permissibility of the system analyzed). The analysis presented in the paper is concerned with the dynamics of a riser initially bent and undergoing heave excitation. Comparison of the results with those obtained using the finite difference and finite element methods shows good compatibility and indicates the correctness of the models obtained by means of the rigid finite element method. Numerical effectiveness of the method enables it to be applied in solving the dynamic optimization problem. The problem described is the compensation of the horizontal vibrations of the vessel or a platform by vertical displacements of the upper end of the riser. Bending moments which arise during the motion of a platform or a vessel can seriously influence and in some cases damage the structure. Thus the aim of the optimization is to ensure that the maximum bending moment at a given point does not exceed its static counterpart. The results of numerical simulations show that the systems enabling heave compensation can be used to minimize the difference between the bending moment caused by displacements of the platform or a vessel and the static moment.

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Section: Optimisationmentioning

confidence: 99%

Compensation of top horizontal displacements of a riser

et al. 2016

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“…A crucial approach in classification of researches is the structural model of riser. A riser can be modeled as a tensioned rod [1] or a tensioned beam. The underlying assumption for modeling the riser as a beam is that the flexural rigidity of riser can't be neglected [2][3][4][5].…”

Section: Introductionmentioning

confidence: 99%

On the selection of boundary conditions for top tensioned risers facing wave induced vibrations

Haghayeghi¹,

Ketabdari²

2018

J. vibroeng.

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Abstract. The severe ocean environment is obviously the source of many uncertain random loads on offshore structures. This harsh environment when acting on the slender top tensioned risers with high aspect ratio (L/D) causes multimodal vibration leading to fatigue failure. Thus, a reliable stress analysis procedure should be applied in the assessment of their long-term behaviors. This research is a study on the effect of boundary conditions on the total and local response of offshore risers due to loads in different sea states. A FEM code is developed for discretization of riser's structural model and was run for the riser of Amirkabir semisubmersible vessel for 87 sea states in the Caspian Sea and four boundary conditions. The results show that the most severe stresses in the riser don't happen essentially in the harshest environment. The comparison of boundary conditions shows that clamped-clamped boundaries lead to lowest stress values while the riser experiences a wider band of stress in the pinned-pinned boundary type. While the riser top end boundary condition highly influences the displacements and stresses even in the lower part of riser.

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“…Rustad et al used finite element method to build a mathematical model of an ocean pipeline system consisting of a tension leg platform, a pair of risers, environmental forces and hydrodynamic interaction [10]. Hong et al developed a novel method for analysis of 3D nonlinear dynamic of marine riser and pipes [11].…”

Section: Introductionmentioning

confidence: 99%

Three-dimensional coupled dynamic analysis of deep ocean mining system

Dai

Zhang

et al. 2016

Teh. vjesn.

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Original scientific paper A new three-dimensional coupled dynamic model of the deep ocean mining system is developed. The seafloor tracked miner is built as a 3D single-body vehicle model with mesh element track-terrain interaction mechanics model, which not only can realize the fast dynamic simulation in contrast to traditional 3D multi-body model, but also can allow the loading of the seafloor sediment special terramechanics model. The mining pipeline is built as a 3D multi-body discrete element model that is divided into rigid elements linked by flexible connectors, also can realize the fast dynamic simulation for such long pipeline. New integrated mining operation modes for the total system are proposed and simulated, which show that during the whole operation processes, the synchronized stable motion of the total system can be kept well. The dynamic simulation analysis in the paper can provide important theoretical basis and technical reference for structure design, performance evaluation and operation control of the practical deep ocean mining system. Keywords: deep ocean mining system; dynamic simulation; mesh element mechanics model; multi-body discrete element model; 3D coupled dynamic modelTrodimenzionalno spregnuta dinamička analiza sustava iskapanja u dubokom oceanu Izvorni znanstveni članak Razvijen je novi trodimenzionalno spregnuti dinamički model sustava za rudarenje u dubokom oceanu. Kopač koji se vuče po dnu napravljen je kao 3D model kompaktnog vozila s mehaničkim modelom gusjeničara s elementima u zahvatu, s kojim ne samo da se može ostvariti brza dinamička simulacija nasuprot tradicionalnom 3D modelu sastavljenom od više dijelova, već se može također omogućiti nošenje specijalnog terramehaničkog modela za talog s morskog dna. Cjevovod za kopanje izrađen je kao 3D model diskretnih elemenata s više dijelova koji je podijeljen u krute elemente povezane fleksibilnim konektorima, i može također ostvariti brzu dinamičku simulaciju za tako dugačak cjevovod. Predloženi su i simulirani novi integrirani načini iskapanja za čitav sustav koji pokazuju da se kroz cijeli postupak može dobro održati stabilno sinhronizirano djelovanje čitavog sustava. Dinamička simulacijska analiza data u radu može pružiti važnu teoretsku bazu i tehničku referencu za dizajn konstrukcije, ocjenu djelovanja i kontrolu rada praktičnog sustava iskapanja u dubokom oceanu.

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FEM modelling and automatic control for collision prevention of top tensioned risers

Cited by 36 publications

References 19 publications

Compensation of top horizontal displacements of a riser

Compensation of top horizontal displacements of a riser

On the selection of boundary conditions for top tensioned risers facing wave induced vibrations

Three-dimensional coupled dynamic analysis of deep ocean mining system

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