| Over the past few decades, world consumption of liquefied natural gas (LNG) has increased more than five-fold and it is predicted that this growth will continue to be very strong. The LNG is stored in specially engineered and constructed double-walled storage tanks which are essential for receiving and safe storage of the liquid gas. The growing world-wide use of LNG has seen the development of significant LNG storage tank facilities for LNG exporters and importers. However, unexpected structural failure of such huge structures by earthquakes may result in not only severe environmental contamination but also tremendous loss of human and financial resources. In order to ensure the safety of the LNG storage tanks, an earthquake-proof structural design is a matter of primary concern. For such an earthquake-proof design, the accurate free vibration characteristics analysis and seismic analysis with reliable earthquake record are of a great importance.The LNG storage tanks with the full capacity of160000m3are the most common used in practice. A fine finite element method was employed to study the dynamic characteristics of LNG tank based on software ANSYS. The mainly aspects are as follows:1. A fine finite element (FE) model for the160000m3LNG tank with reasonable element types, mesh dimension and boundary conditions was established using the finite element software ANSYS. In this study, a finite element modeling method for fluid-structure interaction (FSI) was proposed and the multi-physics coupling method of the fluid and structure was used to investigate the aseismic behavior of the tanks. Also, the different operating conditions were introduced in this study.2. To investigate the natural vibration characteristics of the160000m3full capacity LNG storage tank, the natural vibration characteristics of the tank is obtained when the tank is empty or full and leak at full or harf full liquid level by using direct coupling method for the fluid-structure coupling constraints and the reduced mothed for analysis. The liquid's influence on the vibration characteristics of tank structure is given. Besides, the influence of the prestress, the pressure of the gas and the constraint at the bottom of the outer tank structure is considered.3. In this study, the El-Centro, Taft and artificial ground motion with the peak ground acceleration of0.22g were used for time history analysis. Different work conditions, different earthquake directions were taken into consideration when investigating the seismic response of LNG tanks. The influence of different load directions was compared in order to ensure the worst load direction for the tank structure. Different combinations of the loads were taken into account for the time history analysis. The result showed that earthquake load was one of the most important loads for LNG tank.4. To investigate the influence, two kinds of FE model were established in this study. In model1, the structure was of the the hinged boundary condition at the base. The pile-soil interaction was taken into consideration in model2by using spring dashpot elements. The free field amplification is carried separately by the software DEEPSOIL, and then the resulting motions at the elevations of the near-field elements are used as input. Compare the structure seismic response in different models and work conditions to investgate the influence of pile-soil interaction on calculate the structure response under seismic loading. |
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