STOCHASTIC WIND ANALYSIS OF TALL CHIMNEY
ABSTRACT
A chimney is generally a wind sensitive structure. Tall chimneys ranging from 200-500m high or normally constructed to discharge industrial gases to reduce pollution at ground level. Taller the chimney lesser the pollution level at the ground. Therefore, it is necessary to understand the exact dynamic behavior of tall chimneys subjected to wind. The quantitative estimate of wind effects on tall chimney is very difficult. Wind has got a time-average or static part which can be quantizable to some extent. The most complex part of wind is its time dependent part which is difficult to quantize and is complex too. In the present study, an attempt has been made to quantize the ‘time dependent part’ of wind. In the analysis, stochastic concept of wind analysis has been incorporated. Spectral density function as proposed by Davenport has been used in the analysis. The spectral density function gives the spatial distribution of the frequency of the excitation force, generated by the dynamic component, confronting the structure. A fully developed flow continuum has been assumed to prevail, encompassing the vicinity of the structure. The chimneys have been analyzed by using ¢¢Gust factor method¢¢ of IS:875(Part 3)-1987 and compared with results obtained by the proposed analysis. Codal method found to be unsafe in many cases. Some parametric studies also have been made and discussed.
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