ABSTRACT:

Driven by cost, project characteristics and the need to use local technologies in offshore projects in developing countries, DNV and MCS Kenny have led a second phase of the Spiral Welded Pipe JIP, which aimed at qualifying spiral welded pipe for offshore shallow water applications. This paper focuses on the finite element (FE) study performed as part of the qualification program and aimed to investigate the response of spiral welded pipe to different loading combinations and particularly to S-lay conditions. This paper provides benchmark and guidance to designers of spiral welded pipe for offshore applications regarding its points of strength and areas that require special attention. In the paper, issues such as quality control, tolerances and loading conditions (e.g., load controlled vs. displacement controlled) and how they affect the pipe response are discussed. Detailed analysis and discussion are presented on limit states highlighted in DNVs standard for submarine pipelines (DNV OS F101), such as burst, collapse, axial tension, local buckling and combined loading. The analyses comprised nonlinear 3D FE simulations of spiral welded pipe, using Abaqus, and taking into account relevant tolerances that were likely to affect its limit states and response to loading and installation conditions. The paper touches on non-proprietary conclusions and findings of the FE study regarding the above limit states and how spiral welded pipe fairs compared to other types of pipes commonly used in offshore applications, namely seamless and UOE pipes, as predicted by codes such as DNV OS F101. The presented FE work, together with other studies of the Spiral Welded Pipe JIP, provides needed information that supports confidence in the analysis and design procedures of this type of pipe, which is less costly and more readily available in more areas of the world.

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