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Investigations on Other Types of Tanks

The research on other types of tanks has also provided improved insight into the dynamic behavior of anchored tanks. Several investigations for other types of tanks have helped to clarify the complex behavior of fluid vibrations in flexible containers.

Liquefied natural gas (LNG) tanks are very common type of anchored tanks. They are, usually, composed of two tanks: inner tank and outer tank. The inner tank is directly in contact with the liquefied natural gas and cold gas vapor. Several researchers have investigated the coupled gas-liquid-structure systems in order to understand the seismic behavior of these tanks. Thompson [269] investigated the response of double-walled cylindrical storage tanks. Joos et al [134] developed an analysis that applies to such systems in which a hydrodynamic transient response of the gas creates pressure forces dependent on the flexibility of the liquid boundary surfaces. Identical experiments were conducted on two geometrically identical cylindrical tanks, one of which was rigid while the other was flexible.

Asai et al [9] instrumentally observed earthquake responses of an on-ground LNG storage tank having a pile group foundation. The objectives of the study were to examine whether behavior patterns other than those considered during the design exist and to ascertain safety margins in the current aseismic design. They remarked that the buckling vibration due to the liquid-tank shell interaction was observed but has small influences, the ground deformation effect predominates in the bending moment on the piles, and scaled up observed moments on the piles were half those of estimated in the design. Haroun and El-Zeiny [81] provided an aseismic design guidelines for LNG tanks. Haroun's mechanical analog was used to evaluate the seismic demand on the LNG tanks and compare it to the seismic capacity of the tank to evaluate its safety.

Other configurations of anchored tanks were also investigated. Pavlovic et al [216] conducted a comprehensive parametric study for the problem of thin spherical containers filled to capacity with liquid. The investigation placed particular emphasis on the effect of the bending disturbances arising at the support location.

Solutions to tanks supported on towers were also attempted. Haroun and Lee [89] presented a finite element analysis of axisymmetric shell towers supporting elevated, liquid-filled vessels. The tank tower was modeled using a curved high order ring element while the liquid was accounted for by coupling the liquid added mass matrix to the consistent mass matrix of the shell. They used a mechanical model which takes into account both the flexibility of the tank wall and the global rocking motion of the vessel. In further works, Haroun analyzed tanks supported on x-braced frames ([93], [94]). Buckling of elevated tanks has also been investigated by Allen et al [5].

In addition to elevated tanks, large-sized, multi-walled coaxial cylindrical tanks have been studied in recent years. Since various kinds of oil can be stored in these tanks, it is common to find such tanks in oil industrial facilities. Yoshida [295] described theoretical studies of coupled vibrations of the contained liquid and the shell plate of such tanks in response to lateral earthquake excitation by the finite element method. He analyzed the buckling motion which occurs in the relatively high frequency region due to flexibility of the shell.

The LMR reactor tanks were also studied. Chang et al [30] presented a method for the seismic analysis of these tanks. Mathematical models of a reactor tank and an LMR plant were given. They described various methods of seismic analysis suitable for the analysis of fluid-structure interaction of LMR plant and their advantages and drawbacks. Emphasis was placed on the efficiency of the numerical algorithm. They presented the computer code FLUSTR-ANL that was developed for the seismic analysis of LMR components.

next up previous contents
Next: Evolution of Seismic Analyses Up: Historical Background Previous: Free Vibration Studies
A. Zeiny