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The behaviour of flexible riser tensile armour in the region of an end fitting

Martindale, HGA; (2006) The behaviour of flexible riser tensile armour in the region of an end fitting. Doctoral thesis , UCL (University College London). Green open access

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Abstract

This is a study of axial and transverse slip in helically wound armour wires on flexible pipe under the influence of end restraint. Analysis of steel strip layers in order to find the effect of end restraint prompted the development of a new model to describe their behaviour. This avoids the shortfalls of adapting previous models designed either for similar but different structures or for application away from any end fitting restraint. Previous analytical solutions concerning flexible pipe tensile armour have concentrated on pre-defined paths on the supporting surfaces, these being strained helices or geodesic curves, and have avoided any consideration of end effects. The work presented here is aimed at finding the path adopted by armour wires approaching end fittings, and the resultant stresses and slip. A model is developed which uses small changes in helical angle along the strip to describe tensile armour configuration as a flexible pipe is bent and stretched. The problem is characterized by a strip on a cylinder at a variable angle to its axis which itself has a variable curvature applied to it. A solution is found by minimizing total strain energy to find stress concentrations and slip characteristics. The simplest case of a straight pipe under tension is solved first, followed by a more typical flexible riser configuration involving bending under tension. The results show that under frictionless conditions tensile armour wire slips to reduce tension and that near the end fitting this slip leads to increased bending stresses in some or all of the wires. The model is applied to typical riser designs for the transport of oil and gas to find the location and level of the greatest increases in stress. Their sensitivity to pipe design parameters is also assessed.

Type: Thesis (Doctoral)
Title: The behaviour of flexible riser tensile armour in the region of an end fitting
Identifier: PQ ETD:593012
Open access status: An open access version is available from UCL Discovery
Language: English
Additional information: Thesis digitised by ProQuest.
URI: https://discovery.ucl.ac.uk/id/eprint/1445688
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