This article presents a numerical model for dynamic analysis of an offshore installation of a spool piece. A spool piece is a pipe element used for connection between a pre-laid pipeline and a structure on the seabed. It is often designed with several knees, to accommodate thermal expansion. The spool piece can be lowered through the splash zone with a close to horizontal orientation, or it can be tilted during the splash zone crossing, to control the flooding and to reduce the wave loads. The spool piece is modelled as several interconnected stiff segments, which can have any orientation. The calculated forces include the distributed weight and buoyancy, and also hydrodynamic loads from regular or irregular waves, either if the segment is fully submerged or partly out of water. Concentrated masses, representing connectors, may be included in the spool piece model. The model is demonstrated through a few selected examples including comparisons with field observations. The calculated maximum forces, which will be used for deriving operation limits, are compared to results from simpler and currently used methods of analysis.
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