Gust-effect factor

Certain simplifications that allow the dynamic response to be reconciled with equivalent static loadings are examined. In earthquake loading the dominant effects are found to occur in the lowest mode for which no cross sectional distortion takes place. In wind loading the dynamic response is spread over several modes. The maximum dynamic tensile stresses at the windward base of the tower can be estimated using simple gust effect factors. 20 refs, cited. 

G = gust effect factor Gf = gust response factor for flexible vessels... 

The gust-effect factor, G, is perhaps the most demanding parameter to calculate, and the results are nearly always in the same predictable range. Paragraph 6.5.8.1 of ASCE 7-2005 [2] defines a rigid structure as one in which the strac-ture s fundamental natural frequency is equal to or greater than 1 Hz. Eor a rigid structure, G = 0.85. A flexible structure is one in which the fundamental... 

This paper discusses the impact of wind action on natural-draft cooling towers. The structure of 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. It is shown that the resonant response is small even for very high towers, however, it increases linearly 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 accurate. 11 refs, cited. 

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