Analyses |
 
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Analyses |
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The nodes at the pipeline extremities are fixed in all translational degrees of freedom, and a rotational constraint in DOF 5 is included at the first node to prevent static determinacy. Additional restraints in the vertical direction are applied at regular intervals of 20m along the pipeline to position the pipeline above the arbitrary seabed.
All vertical constraints along the length of the pipeline and the horizontal constraints at the second end are removed. Significant mass damping is specified to minimise initial transients, and the pipeline settles quickly over the seabed under the action of gravity and buoyancy.
A piecewise-linear current is applied to the pipeline. As pipeline motion is constrained by seabed friction, all boundary conditions, except the DOF 5 restraint at the first end, are removed.
A regular wave of amplitude 5m and period 18s is applied. The boundary conditions remain unchanged and are carried through automatically from the current analysis. The dynamic analysis is run for 15 wave periods, at a time-step of 0.5s, to ensure steady conditions become established.