Dynamic Stress due to End Effects in of Non-bonded Flexible Pipes

Abstract

In oil and gas industry, flexile riser is a crucial component for the production system which connected the seabed and the floating units. At the upper end of the flexible riser, bend stiffener is added to reduce the over bending. Flexible riser is mainly made of non-bonded flexible pipe, tensile amour layer is the crucial layer for sustain the longitudinal force. In this thesis, the maximum fatigue damage and stress components of the tensile amour layer are studied. The gap between the end fitting and the bending stiffener can decrease the end effects, in this thesis the effect of increasing the gap length is to be analyzed. In this thesis two kinds of cross-section- ITCODE31 and ITCODE0 are analyzed. For each cross-section, two different load conditions are analyzed, one is with low longitudinal force (0.1MN) and the other one is with high longitudinal force (0.5MN). Under each load condition, models with different gap length (0, 0.25, 0.5 and 0.75 pitch) are analyzed to study the effects on fatigue and stress components. Under 0.5MN longitudinal force, two more cases (1.5 and 3pitch length) are analyzed to better study the convergence of the gap effect. At last, friction sensitive study is performed. Three friction factors: 0.1, 0.15 and 0.3 are analyzed and compared.