A NON-LINEAR ANALYSIS OF LYING A FLOATING PIPELINE ON THE SEABED

摘要

In this article, a model for the determination of displacements, deformations and tensions of a submarine pipelinernduring the construction is presented. The process is carried out from an initial floating situation to the final layingrnposition on the seabed. The existence of currents and small waves is also considered.rnFirst, this technique, usually applied to polyethylene pipelines, is described in this paper as well as some real worldrnexamples, as well as the variables that can be modified to control the behavior of the structure. A detailed descriptionrnof the actions in this process is considered, specially the ones related to marine environment, as Archimedesrnforce, current and sea waves. The structural behavior of the pipeline is simulated by an elastic geometrically nonrnlinear dynamic model.rnA 2-D beam model. I.e. without transversal deformation effects is developed. In the framework of an updatedrnLagrangian formulation, special care is taken of the numerical aspects related to sea bed contact, follower forcesrndue to externa water pressures an dynamic actionsrnFinally, some subroutines are implemented into ANSYS to simulate the two dimensional case, where the wholernconstruction process is achieved. With this software, a sensibility analysis of the bending moments, axial forcesrnand stresses obtained with different values of the control variables in order to optimize the construction steps.rnThese control variables are, the axial load in the pipe, the inundated inner length and the distance of the controlrnbarge from the coast.