Vibration Analysis of Hyperbolic Cooling Towers due to Earthquake Excitations

Abstract

The hyperbolidal shells of revolution supported on columns have been used effectively as natural draft cooling towers of reinforced concrete. The purpose of this paper is to analyze the dynamic response of hyperbolic cooling towers to earthquake excitations. Taking the propagating velocity of earthquake excitations into account, the author shows that hyperbolic cooling towers oscillate not only in beam vibration modes but also in such higher vibration modes as ovalization of their cross sections. When the value αR/V is considerably large, where α and V are circular frequency and propagating velocity of the earthquake excitation, respectively, and R is the radius of hyperbolic cooling towers on the foundation level, numerical example shows that owing to horizontal earthquake excitations an hyperbolic cooling tower oscillates mainly in an ovalization mode and that owing to vertical earthquake excitations it oscillates mainly in a rocking mode.