Elastic Plastic Stability Analysis of Earthquake Loaded Tanks

Abstract

An engineering approach is presented for the earthquake resistant design of cylindrical liquid storage tanks based on the calculation of the maximum dynamic pressure distributions caused by horizontal and vertical earthquake excitation and stability considerations with respect to buckling of the tank wall. Three different possibilities for superposing the dynamic pressure components due to the horizontal and the vertical earthquake components on the static pressure and the different modes of wall instabilities are discussed. The results show that the dynamic pressure component caused by vertical excitation must not be neglected especially for tall tanks. The behaviour of unanchored tanks is investigated, using a finite element shell-spring model. The influence of the increased axial membrane force on different kinds of tank wall instabilities is shown. An essential aim of this project has been the development of simple formulas and diagrams for engineers dealing with the construction of liquid storage tanks made of steel. These formulas have been derived from numerous nonlinear computational analyses.