Research Of Several Problems Of Ultra-large LNG Storage Tank

As one of the three major energy sources in the world,natural gas holds the advantages of clean and efficient,easy to use and rich in reserves,so favored by all countries.China's natural gas reserves can not meet the use requirements.They need to be imported from abroad and stored in liquid form,so that they can be rationally allocated and used.Because liquefied natural gas has the characteristics of volatile,flammable and explosive,therefore,as the main storage container of LNG,the safety of LNG storage tank during construction and earthquake becomes more and more important.At present,there are few researches on ultra-large capacity LNG storage tanks at home and abroad,hence,this paper,based on the ANSYS which is a large finite element analysis software,conducts studies on the stability of the steel dome,the pouring process of the dome concrete and the seismic response of the important structure of the 200 000m3 LNG storage tank.The main contents are as follows:1.The refined model of steel dome of LNG storage tank was established and the eigenvalue buckling analysis and the whole process stability analysis of reticulated shell with steel plate were carried out.Then the buckling modes of reticulated shell with steel plate were obtained,the load-displacement curves of the whole process of the structure were plotted,and the influence of the initial imperfection of the structure on the stability was analyzed.2.Based on the multi-point restart analysis,the concrete pouring process of LNG storage tank dome was simulated,and the internal force and displacement responses of steel dome during different construction stages were obtained.3.The seismic response of the whole model of the LNG tank was studied.The seismic responses of some vital parts,such as the inner tank and the bottom wall joint weld,the suspended ceiling and suspender,and the insulating layer on the tank bottow,were obtained.And the sloshing effect of the LNG liquid was also studied.4.The effects of isolation bearings on seismic response of LNG storage tank and liquid sloshing were considered.It can be found through research and analysis,that the elastic stability bearing capacity plays a controlling role in the stable allowable bearing capacity of the steel dome,and the initial imperfection has a great influence on the stability of the steel dome;In the process of concrete pouring,the stress and displacement of steel dome increase first and then decrease,and they all meet the requirements of the relevant specifications in each construction section.Under the combined conditions of earthquake and hydrostatic pressure,the internal pressure of LNG tank is large;the sloshing height of LNG liquid is high,and the reinforcing ring of tank wall can effectively prevent the leakage of LNG liquid;The bottom ring beam can protect the heat insulating layer at the bottom of the tank;Stress concentration exists in the welding seam of the bottom and wall of the inner tank,and the welding foot size,groove size and the distance between the bottom wall of the inner tank will affect the stress response of the welding seam of the bottom and wall of the inner tank;Seismic response of LNG tanks can be effectively reduced by isolation b earings.