THE RESPONSE OF CHIMNEYS TO WIND-INDUCED LOADS AND THE EVALUATION OF THE RESULTING FATIGUE DAMAGE

The aerodynamics of circular sections depend to a great extent on scaling parameters such as Reynolds number and the turbulence length scale. The inability of modern boundary layer wind tunnels to correctly simulate these factors detract from the usefulness of such experiments and require that modifications be made before they can be applied to prototype scale. In this dissertation, it is suggested that a better approach is to use a theoretical model which depends on empirical parameters obtained from both wind tunnel tests and full scale measurements. In this way expensive, time-consuming tests can be replaced by simpler studies which explore, in a more general way, the aerodynamics of the circular cylinder.;One such model is described in detail. It is based on the representation of the across-wind forces as those due to vortex shedding, lateral turbulence and motion induced effects. The input parameters required for reliable predictions fall into the categories of structural, meteorological and aerodynamic variables. A literature review is included to illustrate the variation of these parameters and to aid in the appropriate choice for particular situations. A series of wind tunnel experiments are described which were carried out on both fixed and elastically mounted pressure models to determine the influence of Reynolds number, small scale turbulence and proximity effects on the aerodynamics and motion induced forces.;Full scale data from a group of 64 steel chimneys and 5 reinforced concrete chimneys of various sizes are examined in order to define appropriate input parameters for real situations. These data indicated a large degree of scatter due to variations in aerodynamic and environmental conditions which suggests that a more reasonable approach is some kind of upper bound solution. A graphical design model is presented which yields conservative results for both steel and reinforced concrete chimneys.;The evolution of design in the direction of efficiency and flexibility leads to the possibility of the degradation of the construction material due to stress cycling or even fatigue failure. The process of fatigue is outlined and the accumulation of fatigue damage due to randomly generated wind load is examined. A method for the estimation of this damage which is based on probabilistic theories is presented and applied to the case of the across-wind loads on chimneys.