Behavior of offshore pipelines subjected to residual curvature during laying
- Statoil, Trondheim (Norway)
- Norwegian Inst. of Technology, Trondheim (Norway)
During S-lay installation of offshore pipelines, the pipe is exposed to plastic strains when the pipe passes over a stinger exceeding a certain curvature. This means that the pipe leaves the stinger with a residual curvature. When passing the inflection point, the bending of the pipe is reversed, i.e. the residual curvature has to be overcome. This occurs partially through bending and partially through twisting. The twisting is here referred to as roll. Three different models are established to investigate the roll phenomenon. Firstly, a simplified analytical energy approach is presented. Secondly, 3D pipeline installation is simulated in a nonlinear FE-program. Finally, a solution of a governing differential equation for the roll based on a 2D pipeline configuration is found. The purpose is to quantify the roll angle and the as-laid state of strain and geometry for specified laying conditions. Furthermore, dimensionless graphs predicting roll initiation and roll angle magnitude are presented. The results show that if plastic deformations occur on the stinger, roll is likely to occur due to the reversed bending in the underbend. Thus, the primary consequences of the plastic deformation over the stinger and subsequent pipeline roll in the underbend are additional strains and stresses in the as-laid pipe.
- OSTI ID:
- 205499
- Report Number(s):
- CONF-950695--; ISBN 0-7918-1311-8
- Country of Publication:
- United States
- Language:
- English
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