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A Study on Elephant’s Foot Buckling in Cylindrical Steel Storage Tanks using Finite Element Nonlinear Analysis

Sangi, Salman | 2011

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  1. Type of Document: M.Sc. Thesis
  2. Language: Farsi
  3. Document No: 42183 (09)
  4. University: Sharif University of Technology
  5. Department: Civil Engineering
  6. Advisor(s): Moghaddam, Hassan; Ghaemian, Mohsen
  7. Abstract:
  8. Considering the role of fluid storage tanks within or after an earthquake and the irreparable damages of such structures that arise from the flammable or toxic nature of the fluids stored in them, it is very important to ensure stability and durability of the tanks under seismic loading. One of the most important damages to storage tanks within the past earthquakes has been lack of stability of their shells taking place in the form of a local bulge of wall, known as “elephant foot buckling’. This phenomenon is a subsequent of high levels of hoop tension, which is a result of containing liquid pressure, along with axial load of surrounding walls. Recent studies reveal that there is no comprehensive and exact criterion to prevent that type of damages in the current codes. Therefore some failures are reported during earthquakes on account of poor designed structures. Hence the mechanism of this kind of failure and tank’s behavior when subjected to an earthquake was investigated in the current study. 30 anchored storage tanks, each one fully fixed at the bottom to a rigid foundation, were modeled using finite element software, ANSYS. Tanks were subjected to various vertical and horizontal accelerations with different magnitudes. Results show that in fact it is not the axial loading that eventuates in buckling, but it is a consequence of yielding of shell due to considerable hoop stress in the presence of relatively low magnitudes of axial loading. Also it has been observed that under the similar loading the tank behaves in the same manner after buckling. Another remarkable phenomenon that was observed and mentioned is “strain jumping” which may emerge after local plasticization of the shell
  9. Keywords:
  10. Finite Element Method ; Elephant Buckling ; Fluid-Structure Interaction ; Liquid Storage Tanks ; Elastic Buckling

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