| Liquefied Natural Gas(LNG),as the cleanest fossil energy,is widely promoted and utilized in recent years.LNG storage tanks are also the core buildings of liquefied natural gas receiving stations and liquefaction plants.In case of earthquake disaster,storage tanks may be damaged,causing serious economic losses and environmental pollution.Therefore,it is necessary to carry out seismic response analysis of LNG storage tanks.In this paper,a method of seismic time-history analysis of storage tank considering bidirectional fluid-structure coupling is established to study the dynamic response of storage tank during earthquake,and the influence of reinforcement ring of inner tank and isolation device on the seismic response of double steel wall storage tank is discussed.The main work and achievements are as follows:(1)For a 4×10~4m~3 steel inner tank,considering the bidirectional fluid-structure coupling,the finite element model of concrete cap-tank-liquid is established,and the seismic time-history analysis is carried out.Firstly,the natural frequencies of dry and wet modes and liquid shaking modes of empty,half and full tanks are investigated.It is found that liquid shaking is dominant in liquid shaking mode,and its natural frequency is much lower than other modes.Secondly,an artificial seismic wave with a designed basic seismic acceleration of 0.15g is fitted according to the site type and soil type of the tank construction area.Then,a method of seismic time-history analysis of storage tank considering bidirectional fluid-structure coupling is proposed,and the simulation method is verified by the seismic platform test of a model tank in public literature.Finally,the seismic time-history analysis of a 4×10~4m~3 steel inner tank is carried out,and the safety of the storage tank under the artificial wave loading process is discussed from the aspects of tank wall stress,tank wall deformation and liquid shaking wave.(2)For the double-steel wall LNG storage tank,considering the steel outer tank and the cooling structure between the tanks,the seismic time-history analysis based on bidirectional fluid-structure coupling was carried out to obtain the stress distribution and liquid sloshing change curve of the storage tank during seismic motion.The dry and wet modes and liquid shaking modes of the whole model of the steel outer tank and the double steel wall tank were simulated,and compared with the steel inner tank,it was found that the natural frequencies of the liquid shaking modes of several models were of the same order.The seismic response analysis of the integral model of the double steel wall tank shows that the stress and deformation of the inner tank in the double steel wall tank are reduced to different degrees compared with the single inner tank model,which indicates that the cooling structure has a certain inhibition effect on the seismic dynamic response of the inner tank wall,but has little effect on the liquid shaking wave height.In addition,a double steel wall tank model with inner tank stiffening ring is established.It is found that the influence of inner tank stiffening ring on the stress and deformation distribution of the tank wall is less than 1%,but it can effectively restrain the sloshing of the liquid in the tank.(3)A storage tank model considering basement isolation is established,and the influence of isolation structure on the seismic response of storage tank is studied.With reference to the natural rubber bearing,the spring element was used to simulate the isolation structure,and it was introduced into the concrete cap-tank-liquid model of a single inner tank.The seismic time-history analysis was carried out,and the influence of the isolation structure on the seismic response of the tank was discussed.The results show that the isolation structure has a certain degree of inhibition on the stress and radial deformation of the tank,but has no significant effect on the liquid shaking wave height. |
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