Seismic analysis and strengthening of cylindrical steel storage water tanks

Cylindrical steel storage tanks are widely used for the storage of various liquids, industrial chemicals and firefighting waters. Liquid-storage tanks have many different configurations; however, in this study, cylindrical ground-supported liquid steel tanks are preferred due to their simplicity in design and construction as well as their efficiency in resisting hydrostatic and hydrodynamic applied loads, when compared with other configurations. This thesis focuses on the seismic design ground supported cylindrical (vertical) steel liquid storage tanks. Dimensions of cylindrical open-top, flat-closed, conical-closed and torispherical-closed-top tanks were determined for 3D-finite element method (FEM) models in an ANSYS Workbench software. The seismic analyses were conducted under the El-Centro and Kobe earthquake loads at different shell thickness and roof types of cylindrical steel tanks. Directional deformation, Equivalent stress, and buckling results presented for both impulsive and convective masses respectively. The results show that the directional deformation tanks is seriously reduced in conical and torispherical closed. On the other hand, it is observed that there is no advantage of flat-closing tanks. When shell thickness is increased, it is observed that directional deformation does not decrease in flat-closed tanks and that directional deformation and buckling occur on the flatly roof. One purpose of this thesis is to strengthen of the cylindrical steel liquid tanks. The tanks were covered with epoxy-carbon composite material. In this study, the directional deformation was observed to reduce in the epoxy-carbon wrapped tanks using the finite element method. Suggestions have been made to strengthen epoxy-carbon tanks, emphasizing that a 4 mm thickness tank may have better performance than an unprotected 6mm thickness tank. Finally, El-Centro earthquake recording was used as a displacement value for 0.22 seconds in order to be able to see the plastic deformations that took place in the tank walls with the effect analysis carried out under short earthquake load. As a result of this analysis, results similar to those of buckling that occurred in the earthquakes were revealed.