Seismic Response Analysis Of 160000m~3 Full Containment LNG Storage Tank

With the rapid development of LNG storage tanks construction, the security issue of large LNG storage tanks has aroused tremendous attention under earthquake action. But the current researches on LNG storage tank seismic performance rarely take the steel reticulated shell of dome into account. The paper will take a 160000m3 full containment LNG storage tank for example,considering the steel reticulated shell of dome,research on the seismic response analysis and emphatically analyze the specific impacts on the seismic performance of large LNG storage tank that the steel reticulated shell products. It will provide reference for security issue analysis and engineering design of LNG storage tank.The main research results are as follows:(1)Based on the ANSYS finite element program, modal analysis on LNG storage tank with and without steel reticulated shell are respectively studied, the results shows that, the first ten frequencies of two kinds of structure system are up to a difference of 1%, the difference is 0.04Hz (third and fourth step),and the first five mode shapes of whole tank structure (including the inner tank, the outer tank and ribbed steel reticulated dome structure)are circumferential vibration wave shapes on the outer tank and dome connection area.(2)The equivalent inertia force and static load are respectively applied on the tank model with and without rib steel reticulated shell. The results show that the steel structure can reduce the vertical displacement of the dome, the most evident effect arises in the dome intermediate region. The vertical displacement reduces 1.2%, maximum is 0.1mm;can reduce outer tank radial displacement by 1.9%, the most evident effect arises in the dome bottom, maximum is 0.09mm;However, the weight of ribbed steel reticulated structure will increase the hoop tensile stress on outer tank top region, maximum is 0.2MPa. Therefore, steel reticulated structure weight should be reduced on the basis of meeting the steel structure strength and stiffness designing.(3)The local area of the prestressed concrete outer tank does not meet the crack control requirements under earthquake action. The seismic response is analysed by time history analysis method with three kinds of seismic waves. The results show that, the trend of the displacement curves obtained from the equivalent inertia force method is the same as that of time history analysis method, proving the feasibility of equivalent inertia force method. The difference between the two results is 2.089mm, appears at the top of the outer tank wall. But in the analysis of the two methods, there are cracks in the upper part of the prestressed concrete external tank, so the area should be considered to increase the prestressed reinforcement to meet the crack control.