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Structural flexible pipes models for the offshore industry: new approaches through the finite elements method

Grant number: 14/22528-0
Support type:Scholarships in Brazil - Doctorate (Direct)
Effective date (Start): March 01, 2015
Effective date (End): February 28, 2018
Field of knowledge:Engineering - Mechanical Engineering - Mechanics of Solids
Principal Investigator:Celso Pupo Pesce
Grantee:Caio Cesar Pereira Santos
Home Institution: Escola Politécnica (EP). Universidade de São Paulo (USP). São Paulo , SP, Brazil

Abstract

The oil and gas extraction in deep waters requires the use of flexible pipes and umbilical cables. These types of structures have proven their effectiveness over the last decades, especially in the Brazilian ultra-deep water oil fields. Flexible pipes are composed of several layers, to resist to all kind of loads. Such a geometry results in a very flexible composite structure resistant to combined pressure, axial, torsional and bending loads. The complexity of these structures led to the development of structural models based on analytical and semianalytical calculation. The Finite Element models (FE) are powerful tools supplementing analytical results. The analytical methods are more practical, but restricted. The Finite Element Method (FEM) is more comprehensive, but involves several other difficulties, dealing with the correct representation of geometries, loads and boundary conditions, as well as the formulation of contact interactions and material behaviors.This research project aims at expanding the development of a finite element approach, which was originally proposed in previous scientific work undertaken by the candidate, with excellent results. This proposal is based on a methodology for simplified geometric representation of helical layers of flexible pipes, with the objective of reducing the numerical complexity, preserving the structural behavior. This task is accomplished by representing helically wound layers as equivalents tubes formed by two materials (the first one representing the steel wires, and the second one representing the gap between the helical elements). Firstly, this model has been studied considering axisymmetric and flexural loads. This methodology will be extended not only with regard to the type of loads, but also with respect to geometric representation, material behaviors and interfacial contact conditions. The results obtained with this particular model will be faced with those arising from analytical models (developed inside the own research group's and found in the technical literature) and experimental results published or available on the Offshore Mechanics Laboratory (LMO) database. (AU)