Numerical Modeling-based Seismic Fragility Analysis Of Base-isolation Vertical Storage Tanks

With the development of China’s petrochemical industry and the national strategiccrude oil reserve project implementation, the earthquake disaster mitigation of storagetanks has become an important research topic. As the uncertainty of the ground motion aswell as the complexity of the tank, the storage tank designed by seismic code would stillbe destroyed by earthquake. The elastomeric seismic-protection isolators system isinstalled between the base and foundation of the tank to shift the fundamental frequency ofa structure away from the dominant frequencies of earthquake ground motion andfundamental frequency of the fixed base structure. Another purpose of an isolation systemis to provide an additional way of energy dissipation, so as to reducing the transmittedacceleration into the structure. The graphical representation of the seismic fragilityanalysis is often regarded as earthquake hazardous, which can be used to predict damageprobability of a certain type of structures under earthquake. Nowadays the research offragility is quite uncommon and there are barely no result of fragility of the base isolationtank. Therefore carrying out the study of the tank damage defense under earthquakedisaster has great important value. The main contents of this paper are as followings.1.The seismic research of the normal and base-isolation vertical storage tanks wereelaborated in this paper. Then the research status of seismic fragility analysis domestic andabroad was introduced. At the same time the method of three types of seismic fragility wasintroduced too.2.A nonlinear finite element model of a1000m3vertical tank was established withANSYS as the research platform while solid-liquid coupling problem of the tank wall andliquid inside the tank was solved. And the accuracy of the model was verified bycomparing with previous studies while modal analysis of the tank has been done.3. The selection of the seismic waves were studied and44far field seismic waveswhich were recommended by FEMA P695were chosen, while PGA was selected to beground motion parameters. Based on earthquake damage characteristics of storage tank which were investigated home and abroad and relevant theoretical studied before, themain failure mode of the tank was confirmed. Departure from the seismic fragility ofperformance function, seismic fragility algorithms was proposed.4. A total of968samples including normal and base-isolation tanks of which peakacceleration had been amplitude modulated were calculated. Finally, the seismic fragilitycurve of normal and base-isolation tanks were established and a comparison of the curveswas done.