Structure Strength Calculation And Fatigue Strength Analysis Of FLNG

Floating liquefied natural gas(FLNG),anchored at the site of operation,is subject to more severe load conditions.The device in the course of the service must have sufficient safety margin,or easily lead to significant property damage or even casualties.There are no cases of structural strength evaluation of FLNG devices by using the finite element direct calculation method for ship in domestic and foreign literatures.In this paper,the finite element direct calculation method is used to analyze the strength of FLNG,and the structural strength of the FLNG device can be evaluated effectively.The results provide a powerful analytical basis for the design optimization of FLNG device,which greatly improves the research and development efficiency of FLNG device.In this paper,the motion response,hydrodynamic pressure distribution and vertical bending moment of cross-section of FLNG under regular wave in arbitrary direction are calculated based on three-dimensional potential flow theory.The hydrodynamic pressure distribution and short term forecast results for vertical bending moment of cross-section of FLNG under irregular waves calculated based on spectral analysis method.Finally,obtain design wave under the condition that the vertical bending moment of the cross section in the ship is the main load control parameter.The hydrodynamic calculation results are provided for the structural strength evaluation of the FLNG.The yield strength of the FLNG device is evaluated by the direct calculation method of the whole ship strength based on the design wave method.The whole ship structure of FLNG device is modeled by finite element software MSC.PATRAN.The automatic loading of hydrodynamic pressure on the wet surface of hull is carried out by compiling wave load automatic loading program based on PCL language.And then load the gravity,hydrostatic pressure,inertia force and catenary tension on the finite element model of FLNG.The stress level and distribution of the hull structure of the FLNG device and the deformation of the whole ship structure are obtained by numerical analysis.The fatigue strength of the FLNG device is evaluated by the direct calculation method of the whole ship strength based on the spectral analysis method.According to the corresponding specification of CCS and the calculation result of yield strength of FLNG device,the hot spot position of fatigue analysis is determined and the model is refined.The stress response transfer function of each fatigue hot spot of FLNG device is obtained after applying the load and the numerical analysis.And based on the Miner linear cumulative damage theory,the fatigue damage degree of each fatigue hot spot of FLNG device is calculated.The fatigue strength of the FLNG device is finally evaluated.