Free and Forced Vibration Analyses of Hyperbolic Cooling Tower Shell Using Harmonic Solid Ring Finite Elements

Abstract

This paper discusses free and forced vibration responses of hyperbolic cooling tower shell which is one of the complex real life applications of axisymmetric structures. 9-noded harmonic solid ring finite element is used in the numerical model of the cooling tower. Physically a three-dimensional cooling tower problem is reduced to a two dimensional one by expressing earthquake loading in the form of Fourier series for a single harmonic with the help of harmonic elements. Therefore, the complete solution for the problem is obtained simply for a single load component that makes the model computationally much more efficient. A computer program is coded in Matlab for the purpose and the results obtained in the study are verified with the results available in the literature. A parametric study is also performed for the variations in shell curvature of the tower. The time history analysis method is used for the dynamic response of the cooling tower shell. Acceleration records of Duzce earthquake is used in the study and the results are presented in tabular and graphical formats comparatively for varying shell curvature. It can be concluded that circumferential mode number and shell curvature have significant effects on the dynamic responses of cooling towers.