r+k has longstanding experience with offshore pipelines, based on the experience with onland pipelines, but extended with the typical sea environment conditions.
Experience with offshore pipelines started in 1972 with a request of Shell UK Expro to assist, based on its onland pipeline analysis developments, with the design and analysis of riser-tie in structures. The start was the interaction between the riser, (attached to the platform structure) and the sea line, (often on a slippery sea floor) with the tie-in in between. Each element has its own conditions and its own contractor and thus its own approach to analysis. That’s why the boundary conditions at the interfaces between these three elements became the problem. The pipeline structure, however, acts as one structure and r+k Consulting Engineers was asked to integrate the behaviour of the pipeline as a whole.
One aspect that evolved from these studies was the development of the dog-leg type tie-in.
Wave and current loadings are a typical offshore aspect. Development and applications in analyses are based on:
- long crested Airy waves
- short crested Airy waves (cross pattern)
- long crested 5th order Stokes waves
- 7th order current parabola (default)
- user-defined current profiles
Other experiences followed, i.e.:
- on-bottom stability
- differentiated riser tie-in structures
- bottom tow and J-tube riser pull-in
- free span analyses
- pipeline self burying
- upheaval buckling (overbending onland)
- incident analysis (e.g. anchor hooking, cable sawing…)