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Analysis of unanchored liquid storage tanks under seismic loads

Peek, Ralf (1986) Analysis of unanchored liquid storage tanks under seismic loads. EERL Report, 86-01. California Institute of Technology , Pasadena, CA. (Unpublished)

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Because of cost, cylindrical, ground supported liquid storage tanks are often not fixed to their foundation, even in seismic areas. For such an unanchored tank made of steel, the weight of the cylindrical shell is mostly insufficient ' to prevent local uplift due to seismic overturning moments. Although, for properly designed connecting pipes, uplift itself is not a problem, it results in larger vertical compressive stresses in the tank wall at the base, opposite to where the uplift occurs. These compressive stresses have often caused buckling, even in earthquakes which did not cause much damage to other structures. Various investigators have studied the behavior of unanchored tanks experimentally, but, due to the complexity of the problem, so far very little theoretical work has been done. Two methods of analysis for static lateral loads are presented: An approximate one in which the restraining action of the base plate is modeled by nonlinear Winkler springs, and a more comprehensive one in which the two dimensional nonlinear contact problem is solved by the finite difference energy method. The theoretical results are compared with existing experimental results and with the approach from current U.S. design standards. The theoretical peak compressive stresses are in good agreement with the experimental results, but in some cases exceed those calculated by the code method by more than 100%. Finally, a new design concept, by which the tank wall is preuplifted all around its circumference by inserting a ring filler is described. It will be shown theoretically and experimentally that this preuplift method substantially improves the lateral load capacity.

Item Type:Report or Paper (Technical Report)
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URLURL TypeDescription ItemAlso published as author's PhD thesis
Additional Information:PhD, 1986: PB-87-232872/A12
Group:Earthquake Engineering Research Laboratory
Series Name:EERL Report
Issue or Number:86-01
Record Number:CaltechEERL:1986.EERL-86-01
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Usage Policy:You are granted permission for individual, educational, research and non-commercial reproduction, distribution, display and performance of this work in any format.
ID Code:26377
Deposited By: Imported from CaltechEERL
Deposited On:12 Oct 2001
Last Modified:23 Aug 2021 23:30

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