Wind Effects on Cooling-Tower Shells

The design of natural-draft cooling towers is dominated by wind action. With respect to the response of the structure the wind load may be divided into a static, a quasistatic, and a resonant part. The effect of surface roughness of the shell and of wind profile on the static load is discussed. The quasistatic load may be described by the variance of the pressure fluctuations and their circumferential and meridional correlations. The high-frequency end of the pressure spectra and of the coherence functions are used for the analysis of the resonant response. In general, the resonant response is small even for very high towers. It increases overlinearly with wind velocity. Equivalent static loads may be defined using appropriate gust-response factors. These loads produce an approximation of the behavior of the structure and in general are sufficiently accurate.