Dynamics of Seabed Pipelines and Study on Critical Free Span Length

Dynamics of Seabed Pipelines and Study on Critical Free Span Length
Authors : Anu Mathew, Dr. T. P. Somasundaran
Publication Date: 03-03-2017


Author(s):  Anu Mathew, Dr. T. P. Somasundaran

Published in:   International Journal of Engineering Research & Technology

License:  This work is licensed under a Creative Commons Attribution 4.0 International License.

Website: www.ijert.org

Volume/Issue:   Volume. 6 - Issue. 03 , March - 2017

e-ISSN:   2278-0181

 DOI:  http://dx.doi.org/10.17577/IJERTV6IS030028


Over the past few years there has been an enormous need for natural resources. The increase in demand of pipelines which are used to carry such natural resources in sea conditions have also been increased which creates a need for research in this area. Offshore pipelines should be stable under the combined action of hydrodynamic and hydrostatic forces. Thus a study is carried on the pipelines resting on sea bed for various hydrodynamic forces. An accurate prediction of response is crucial assessment of the safety of submarine pipelines. Accurate response requires a well -adapted structural formulation and realistic description of both the external loading and interaction between the response and the loading. A MATLAB coding is developed for the prediction of dynamic motion of ocean bed pipelines. An elastic spring system simulates transverse, axial and vertical resistance of the soil. The pressure differential across the pipeline wall modifies the tensile stress and influences the flexural stiffness of the finite element model through geometric stiffness. Hydrodynamic inertia and viscous drag forces are calculated using modified Morison’s equation. The equation of motion during wave activity can be integrated using Newmark-Beta method. The primary features of the work are Modelling pipe as a series of 3D- beam elements , Modelling soil using Winkler’s model , Modelling hydrodynamic forces and Prediction of responses under monochromatic and random wave. Currents are very important underwater, there can be positive or negative currents. For the present study a steady current with constant velocity is allowed to act along with wave and the response is studied. The most crucial part in the area of response due to uneven seabed is the determination of critical free-span length is also included in the present study. Thus all the possible sea conditions are studied in this work to assess the safety of pipelines.


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