Effect of domain frequency of soil-tank to seismic response

Seismic response of liquid storage tanks is quite different from conventional structures not only due to hydrodynamic effects acting on the tank shell but also owing to many sources of nonlinear behavior mechanisms of tanks such as buckling of the tank shell، large amplitude nonlinear sloshing، nonlinear tank_soil interaction، material yielding، and separation between tank base and soil. Because of the assessment of earthquake response of such structures، finite element methods are indispensable tools since they offer a concise way of accurately considering all these nonlinearities in the model. The three dimensional tank was modeled by software of ABAQUS. This paper investigated the effects of foundation on the seismic behavior of tank-foundation–soil system، and also described that the frequency of the soil-structure should be away from the domain frequency of the Fourier amplitude although in standard codes just the frequency of tank was declared. For this purpose numerical investigations are performed on two vertical، cylindrical tanks with different ratios of Height to Radius (H/R=2 and 0. 66) also two type of soils (medium and stiff sandy soil) was considered as a tank foundation. Result shows in tall tank because of excessive settlement and uplifting should be anchored، also as the ratios of height to radius decrease tank became self anchored and could be stable on seismic load، also the Fourier amplitude of the time history had an important effect on the tank response. It was also concluded that by increasing the soil strength parameters due to reducing amplification effect، tanks have better performance.