Study of Dynamic Characteristics of Circular Liquid Storage Tanks Using Acoustic Principles

Liquid storage tanks are lifeline structures, which should be designed with utmost care. Any damage to a tank, which is used to store hazardous liquid is catastrophic. The estimation of fundamental natural frequencies of liquid storage tanks situated in seismic regions is important for a seismic design. The present study deals with the estimation of natural frequencies of circular steel liquid storage tanks with reference to codal provisions and numerical analysis by using acoustic principles with the aid of FEM software. The study has been carried out for circular tank of diameter 6 m and height 8 m with different liquid depths, viz. 1/3rd, 2/3rd and full tank conditions and stiffness conditions, incorporating the sloshing effect. The natural frequencies obtained by finite element analysis of tanks are compared with those values obtained as per various International codes, viz., IS 1893(part2):2014, API 650 and Eurocode 8. The results show that the convective mode frequencies are matching well whereas, there is slight variation in impulsive mode frequency values obtained as per IS 1893.