The primary aim of this project was to assess the scale of damage that occurs during a direct impact between the bow of a shuttle tanker and the stern of a floating production storage and offloading unit (FPSO). A range of collision scenarios were considered with different types of bow shape, stern shape and ballast condition. PAFA had previously derived a modified Minorsky formulae that could be used to estimate energy absorption in collisions based on the volume of damaged steel. This method was to be employed to estimate the penetration of the FPSO stern based on a rigid bow and also for simultaneous damage to both bow and stern. The study initially concentrated on encounters involving horizontal motions only, based on the perception that that the main cause of such incidents was a failure (either temporary or permanent) of the positioning or motive power of the tanker combined with a yaw/sway motion of the FPSO, all of which involve horizontal movement only. However, subsequent consideration of the average sea conditions suggested it would be relatively likely for both vessels to be experiencing heave/pitch motions at the time of such an incident, and that the consequences of such vertical components should be addressed.
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