Research On Global Bending-torsional Strength Of FLNG Under The Extreme Sea Conditions Combined With Single Point Mooring Loads

Floating Liquefied Natural Gas(FLNG)system has been developed as a prospective alternative for offshore gas fields.This paper addresses a study on the global bending-torsional strength of an FLNG vessel moored by the single point mooring system.During the research,the finite element analysis methodology and SESAM software was applied to conduct the investigation on the global bending-torsional strength of FLNG under the extreme sea states with single point mooring loads simultaneously.The deformations of the hull and stress of the cabin sections discussed with the effects of single point loads,and security of the cargo containment system assessed were the focal points and innovations of the reasearch.Some modules of SESAM were used to compelete the calculations during the investigation.The global finite element model,mass model and hydrodynamic model of the FLNG vessel were established by GeniE.In ballast loading,full loading and 75% load conditions,stability analysis have been carried out to correst mass models with compartments of the tanks set based on the loading layout.Choosing load dynamic parameters,and the six degree of freedom motions and load transfer functions of FLNG have been analysed and discussed through Wadam.Based on the environment in NanHai,the long term predictions of wave loading were performed and the design wave parameters were acquired under the extreme sea state.Simulating the 3 hours environment of the one-hundred-years,top tension applied on the mooring lines were performed through the coupling of analysis conbined with the analysis of yaw motions of FLNG.Then the global bending-torsional strengh characteristics and effects of mooring loads on the hull strengh were discussed considering the still water and wave induced loads include mooring loads or not.It is concluded that the global structural rigidity of FLNG is significant and stress level of cargo area is within the safety range.The deformation of the global hull and structural strength of the cargo are less affected by the single point loads.The security of the cargo containment system under bending-torsional deformation of global hull can be guaranteed.This paper has conducted investigation on the global bending-torsional strength of a SPM FLNG facility,which provides some insight and technical support for FLNG designed by our country and provide other marine structures some reference values of structural analysis.