Numerical Assessment of FPSO Platform Behaviour in Ship Collision

Offshore platforms may potentially collide with vessels of various types, including visiting ships such as supply ships and passing ships. The most critical and relevant conditions, including the analysis and design approaches are introduced. Different ship types having different displacements and structural designs exert different vessel impact loads on impacted structures. This paper presents the findings of collision impact analyses of the side shell panel, bow and stern structures of Floating Production Storage Offloading (FPSO) platforms in case of impact, e.g. by a supply vessel or methanol tanker. As collision impact simulations continue to be conducted conservatively, the colliding positions of the striking vessel are presumed to be bow and stern only, with side force. In order to assess hull strength in collision events, non-linear FE simulations were performed by means of the MSC / DYTRAN tool, as these collision events result in more complex reactions. The degree of hull damage suffered by an FPSO vessel in different collision scenarios and at varying impact energy levels was determined in accordance with the NORSOK N-004 standard guidelines. Post-collision analyses were conducted to establish the structural integrity of the damaged hull after being exposed to environmental conditions for one year. The reduction of hull girder strength associated with the worst damage was evaluated and accounted for in the present study, providing no further damage occurs. Furthermore, the acceptance criteria for evaluation and corresponding consequences are calculated and discussed in detail. Finally, the findings from the present paper will help clarify the impact response of offshore structures and evaluation approaches and give valuable guidance for the design and operation of FPSO platforms.

Investigation of the Cost of Future Naval Amphibious Capability

Through the creation of a large number of concept designs, the cost and vessel impact of deploying and supporting amphibious operations has been investigated. The investigation has looked at capabilities such as the transportation and delivery of vehicles, landing craft, aviation and embarked troops in a number of platform types such as LPDs, LHDs and Ro-Ros. A series of trends describing the costs of the capability have been investigated to estimate the cost of individual capabilities within a design. Over the timeframe of the study, vessel manning is predicted to change and a method of predicting the crew requirement has been developed to investigate the impact of reduced manning on amphibious platform designs. This is the first of two stages of work; in the second stage the requirements for a task group will be investigated to determine the best way to deploy capability at a fleet level.