Nonlinear Rocking Analysis of Unanchored Cylindrical Tanks (2nd Report, Dynamic Response with Consideration of Uplift of Bottom Plates)

Abstract

An effective method for calculating the nonlinear rocking response of ground-supported unanchored cylindrical tanks to earthquakes was developed. In this method, tank wall and liquid content are replaced with a mass-spring system, and the nonlinearity associated with the partial uplift of bottom plates due to overturning moments is considered as the rotational spring of bi-linear type which is determined by a static uplift analysis of tank bottom. The reliability of the dynamic analysis was illustrated by computing resonance frequencies, response accelerations and rotation angles of tank models and by comparing them with the results of vibration tests. A seismic design procedure for nonlinear rocking of tanks is proposed, in which the uplift height of bottom plates is calculated by dynamic rocking analysis and the corresponding radial stress of them is obtained by static analysis. And a rocking analysis of a full-sized tank was tried, too. © 1984, The Japan Society of Mechanical Engineers. All rights reserved.