Study On Local Strenghth Analysis Method Of New Type LNG Tank Under Sloshing Loads

Energy shortages and environmental deterioration lead to the increasing needs of clean, low-carbon and high-quality natural gas. The LNG tank, which can be divided into Moss type, membrane type and SPB type, is the main way of maritime transportation of natural gas. Researches on LNG ship of SPB type are comparatively few at present. The local members will suffer varying degrees of sloshing impact in long-term operating conditions. This research conducts local strength analysis under sloshing loads of a SPB LNG tank structure to ensure operational safety. The main contents and conclusions are as follows:(1) Calculating natural liquid motion period, natural ship motion period and sloshing loads in accordance with the classification rules. A finite element modle of target tank was built. Analysis of the response of tanks under sloshing loads is conducted and tank structural safety is thereby checked.(2) Tanks and ship hull structure is connected with supports, which are simulated by solid elements and grounded spring elements in this paper. The effects on finite element analysis causing by different simulation methods are compared. We can find these two methods’ results are similar and both simulation methods are effective ways.(3) The use of sloshing 2D software for simulating tanks’ sloshing loads under different loading conditions of pitch and roll situations was done. The sloshing loads are changing over time and space, further research about how to simplify sloshing loads shows that interpolation, multiply a correction factor after interpolation and segment loading are effective ways of simplification of sloshing loads.(4) Both dynamic response and quasi-static response of the tank are analyzed using finite element method. As for the quasi-static analysis, the dynamic sloshing load is simplified as static using envelope method. The results of the dynamic analysis, quasi-static analysis and structure analysis under sloshing loads calculated according to DNV rules are being compared. Similarities and differences of these three cases are summarizes.