Seismic Response Analysis Of Double-wall Cryogenic Steel Storage Tank

As the hydrocarbon fuel storage containers, double-wall cryogenic storage tank isdeveloping rapidly with the fast demand of world energy. Due to the particularity of itsstructure, it will cause serious disasters on society and environment under the earthquakeaction. In order to research the seismic behavior, this paper selects a50000m3LPGdouble-wall cryogenic steel tank which designed by a designed institute, using ANSYSWorkbench software for carrying out the seismic response analysis. The main works of thispaper are as follows.Firstly, this paper introduces the structure, types, calculation theory and the mechanicsmodel of the double-wall steel tanks in detail. A three-dimensional finite element model oftank is established, including inner tanks and outer tanks separate model and inner tanks andouter tanks connective model. Liquid-solid coupling effect and the relationship between innertank and outer tank have been considered. According to modal analysis, we know that: thevibrational modes of inner tanks liquid-solid basic vibration are all beam vibration, naturalfrequencies are little difference, so it has less influence of outer tanks on inner tanks. Theseparate model of outer tank is high-frequency vibration, among which hoop wave vibrationis the leading one. In connective model, the basic vibration frequency is lower, among whichbeam vibration is also the leading one. It has greater influence of inner tanks on outer tank.And the increasing of liquid storage increases the inherent vibration frequency of theconnective model.For analysis the seismic response, three conditions has been selected, including BOEmoderate seism and SSE. the results show that: the equivalent stress is lower than the materialyield limit and the axial stress of inner tank is higher than allowable critical stress in SSE, sobuckling failure will happen. The insulation layer does not fall off for the low horizontal displacement. the followings are danger zones: axial stress and hoop stress are larger at thelower of tank wall and on the top of outer tank wall, which are easy to cause instability. Frombottom to middle of inner tank wall is prone to buckling failure for the higher hoop stress.While the welded joints of tank wall and bottom board, outer tank wall and roof, stress anddisplacement are so queasy that it tend to cause instability and weld cracking, seismicstandard of storage tank in China is more conservative, and it doesn’t fit for double-wallcryogenic tank.