Displacements in Oil Storage Tanks Caused by Localized Differential Settlement

Abstract

This paper presents design charts for predicting the maximum radial distortion of open-topped storage tanks caused by localized differential settlement of the tank foundations. It is well known that differential settlement can produce radial deflection of the tank shell sufficient to cause jamming of the floating roof. Predictions of shell deflections have often assumed the shell to be inextensional, an assumption which may not always be valid, particularly where the settlement is localized. Consequently, the authors have recently completed a more refined analysis of the deflections and stresses in the shell and the primary wind girder [1] in which the shell is considered to act as a membrane. They concluded that this membrane analysis is valid for all practical applications and proposed a procedure for predicting shell displacements caused by any general differential settlement profile using Fourier analysis. This paper firstly reviews the new membrane analysis and then illustrates its application to two specific localized settlement profiles commonly found in practice to produce easy-to-use design charts. Finally, the paper refers to experimental testing of a model tank, carried out to verify the validity of these design charts [2].