Analyses |
 
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Analyses |
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The pipe is modelled in the initial static analysis for its entire lay length as a straight pipe which extends beyond the vessel bow along a flat guide surface. A series of vertical degree of freedom boundary conditions are used to suspend the pipe in close proximity to the guide surface. The plastic material properties are defined via the *PLASTIC HARDENING keyword using an X65 (steel grade) non-linear stress-strain relationship.
A restart quasi-static analysis is used to release the vertical degree of freedom boundary conditions and allow the pipe to settle onto the flat guide surface. Solution robustness is aided with the addition of some mass damping on the pipe.
A series of dynamic restart analyses are used to simulate the payout of the pipe over the vessel stinger and lowering to the seabed. The initial payout analysis is restarted from the quasi-static release analysis and a displacement boundary condition is applied to the bow end of the pipe to push it over the stinger and lower to the seabed. Once the pipe reaches the seabed, the seabed end is attached to the seabed using a pinned boundary condition and the vessel is offset in the negative surge direction while also applying a displacement boundary condition at the bow end of the pipe. This procedure is carried out in incremental restart analysis steps from the second payout analysis to the last until the pipe is installed in an S-lay configuration.
The full series of installation stages is as follows:
Analysis Name |
Payout(m) |
Vessel Offset(m) |
|---|---|---|
Payout 1 |
600 |
|
Payout 2 |
100 |
100 |
Payout 3 |
60 |
100 |
Payout 4 |
40 |
50 |
Payout 5 |
50 |
100 |
Payout 6 |
200 |
|
Payout 7 |
15 |
100 |