The Evaluation Of Seismic Vulnerability And Retrofitting Steel Oil Tanks

Abstract: In this study, the seismic behavior of five oil storage tanks with height to diameter ratios of 0.39, 0.47, 0.53, 0.63, 1.0 was examined using the powerful software ANSYS and their failure mechanisms, including elephant leg buckling, diamond elastic buckling, failure of roof due to fluctuation of fluid, sliding, overturning, up lift and unsymmetrical tank leakage were assessed. several analyses, including static, modal, spectral (linear), and time history (nonlinear) analyses were done for studying the above parameter on the above–mentioned tanks, and the results were stated. Finally it was realized that if the tank freeboard considered as 0.18 H (H: the tank Height), no roof tank risk shall be present as regards fluctuation of fluid during an earthquake. Also, it was seen that tanks with a height to diameter ratio greater or equal to 1.0 would overturn under the loads applied and are unstable. Other mechanisms studied were all less than the value allowed by the code. It is noteworthy that the tanks in question are located in Shiraz and the results are valid for unanchored, crude oil storage tanks.