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L'abstract ci-dessous sera soumis à IOSC 2005 : International Oil spill Conference, Miami, 15-19 May 2005

Structural Modelling of Oil Spill Containment Booms
by the Finite Element Method

Boushaba Farid,  Serge Nouchi, Youssef Benelmostafa, Frederic Muttin,
Ecole d'Ingénieurs en Génie des Systèmes Industriels (EIGSI)
26, rue de Vaux-de-Foletier 17041 LA ROCHELLE CEDEX 1, FRANCE

> Abstract :

The current design of the antipollution boom proves to be ineffective in order to protect the sea coast from the oil slicks when the marine current exceeds of 1 knot. A few works have been done on the
antipollution floating booms. Thus our works concern the technical research framework of the control aspects of accidental water pollution. It's about developing an antipollution floating boom mathematical model.

In the present work, we consider in the first part the cable element which undergone large displacements and rotations in three-dimensional space. The cable is discretized in finite elements and it undergone drag effects, this force is obtained from fluid mechanics by the marine current. The equilibrium equations are solved by using the iterative method of Newton. The tangent stiffness matrix of a cable segment can be formed as the sum of two parts, namely an elastic stiffness and geometric stiffness. The elastic stiffness is associated with the extension of the cable member, the geometric stiffness is associated with the fact that as a stressed cable member is displaced, the forces it exerts on the nodes at its ends change direction. The cables may be used as anchors under water membrane, dams or as anchors for the floating structures.

In the second part we consider also the assembly of body articulated elements, the solids are assumed to be mounted on systems compose of elastic springs and dashpots. Thus displacements of these articulated solids due to the elastic strain are "drowned" in displacements more important, and the articulated solid movement is similar to the rigid evolution of body. Springs and dashpots elements added to the articulated solid elements allow displacements and rotations in the horizontal plane.

In the third part, we model the ribbon element by using the nonlinear theory of membranes, the ribbon is discretized in rectangular finite element with four nodes by using the Zienkiewicz-Irons isoparametric element, the Newton-Raphson algorithm solves the non linearity of the problem.

The analysis of the cable elements, solid articulated and the ribbon allow releasing certain remarks and observations which make it possible to understand the floating boom behaviour and its dimensioning.

Keywords: cable, boom modelling, membrane, mechanical response, oil containment, finite element, coastal region, current effect.

References

[1] E. Haug  and G. H. Powell. Analytical Shape Finding for Cable Nets. IASS Pacific Symposium Part II on tension Structures and Space Frames Tokyo and Kyoto. Paper N° 1-5, Architectural <?xml:namespace prefix = st1 ns = "urn:schemas-microsoft-com:office:smarttags" />Institute of Japan. 1972.
[2] F. Muttin , F. Guyot, S. Nouchi, and B. Variot, Un modèle simplifié pour le couplage structure/fluide-pollution adapté à un barrage flottant anti-hydrocarbure , Proc. 9èmes Journées Hydrodynamiques, ISSN 1161-1847, Poitiers-Futuroscope, p 267-280, 10-12 mars 2003.
[3] F. Muttin, F. Guyot, S. Nouchi and B. Variot, Experimental Numerical and Optimisation Study of Oil Spill Containment Boom, Proc. of Coastal Environment including Oil Spill Studies, OIL SPILL 2004 Conference, Alicante, Wessex Institute of Technology, p 421-430, 28-30 April 2004.
[4] Haug  and G. H. Powell. Finite element analysis of non linear membrane  structures. IASS Pacific Symposium Part II on tension Structures and Space Frames, Tokyo and Kyoto. Paper N° 2-3, Architectural Institute of Japan. 1972.
[5] D. Gay and J. Gambelin. Dimensionnement des structures. Hermes Sciences Publications, Paris, 1999.
[6] A. Amini, E. Bollaert, J.L. Boillat, A. Schleiss. Preliminary design criteria for oil spill confinement booms. OIL SPILL 2004 Conference, Alicante, Wessex Institute of Technology, 28-30 April 2004.

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