Structural Behaviour Evaluation of Natural Draught Cooling Towers under the Consideration of Shell-Geometric Parameters

Abstract

In the design procedure of the cooling tower the form-finding of the shell is the most important process, because the shape of the shell determines the sensitivity of dynamic behavior of the whole tower against wind excitation. The purpose of the study is the investigation of the influences of the geometric parameters of the cooling tower shell on the structural behavior. The geometric parameters - height of throat, angle of base lintel and radius of top lintel - were analyzed in detail. In the linear analysis the influence of each geometrical parameter will be evaluated by the required amount of the reinforcement steel. The realistic behaviours of the towers with various geometries, found out by geometrically and physically non-linear analysis, will be discussed in detail. Each geometry parameter influence will be evaluated by the comparison of the damage index developments in the tower under increasing wind effect. Herein a damage indicator is defined by means of the modal parameters; natural frequencies and mode shapes varying according to the damage state. As a result, a hyperbolic rotational shell with the small radius overall will yield the shell geometry with a higher first natural frequency and thus a wind-insensitive structure. Linearly and nonlinearly numerical simulations demonstrate influence of the shell-geometric parameters on structural behaviours. The results of this study may be informative for the form-finding of the cooling tower shell.