Gust Factors and Alongwind Pressure Correlations

An expression for gust response factors for tall buildings is derived using an analysis, based on first principles, of three-dimensional structures subjected to random loading. The expression permits an evaluation of the effect of the alongwind pressure correlations, with regard to which differences exist between various methods presently in use. It is found that depending on the assumptions to which they resort in order to take this effect into account, some methods overestimate, while other methods underestimate, gust factor values by as much as 15 to 30%. The expression derived offers, in addition, the potential for obtaining more economical gust factors by incorporating in their structure a more realistic model of the pressure in the wake.