Fatigue Strength Analysis For Large-scale And Membrane Tank LNG Vessels

Fatigue failure is one of the main fail modes of ship structures. Especially for large-scale ships, the fatigue problem should be paid more attentions.Combining with 220,000m3 LNG vessel designed by our country independently, this paper is to research the fatigue strength analysis approach. The main contents are as follows:1) Research the constructional features and the key technologies for structural design of large-scared and membrane tank LNG vessel.2) Research the flowchart of the DLA and spectral-based fatigue analysis approach according to the ABS Guides for structural design of LNG vessel. Check the structural strength and fatigue strength of the LNG vessel, give some modification advices for the fail location. The result shows that the DLA can simulate the actual load of ship, the fatigue strength meet requirement of guides. The structure discontinue near the fore and aft is heavy-stressed, where should be paid more attentions.3) Respecting the LNG is cryogenic, this paper is to forecast the temperature distribution and analysis the thermal stress of cargo hold zone, exploring its affect for structure fatigue life. It can provide valuable reference for researching the fatigue strength of LNG vessel. Research shows that temperature in cargo hold zone distribute uniformly along the fore and aft. Thermal stress in low hopper of cargo hold zone affect the combine stress appearently,but the mean stress fator have not been changed, namely the fatigue life have not been influenced.