The Earthquake Engineering Online Archive

Static tilt behavior of unanchored cylindrical tanks

Lau, David T.; Clough, Ray W.

UCB/EERC-89/11, Earthquake Engineering Research Center, University of California, Berkeley, 1989-09-01, 206 pages (510/L29/1989)

Many unanchored cylindrical tanks have been damaged during recent earthquakes due to uplift. Because uplift is an extremely complex nonlinear dynamic problem, this report describes a study of the related nonlinear behavior resulting from static tilt to the tank base. A preliminary investigation of the axisymmetric uplift is carried out to gain insight into the resistance mechanisms for the static tilt problem. A partially filled tank is subjected to an effective static lateral acceleration component which simulates the effect of the horizontal acceleration component of an earthquake. The most important resisting element of the tilted tank is the bottom plate which is uplifted from its support over a portion of the base, leaving a practically circular-shaped region in contact with the foundation. An effective analysis procedure has been developed to study the static tilt behavior. Detailed analytical results are presented for a broad 1/3-scale welded aluminum tank with tilt angles ranging from 4 to 16 degrees. Displacements and principal stresses for the base plate are presented. The relative importance of the membrane action and the bending mechanism in the base plate uplifted region is discussed by means of a defined geometric stiffness index. Analytical results are correlated with measured data obtained during a previous investigation. A limited part of the complete set of analytical results of another similarly scaled tall model tank is also presented.

Available online: http://nisee.berkeley.edu/documents/EERC/EERC-89-11.pdf (9 MB)