Purpose and Scope In Item No. 82026 data are provided for estimating the variation of the design mean-hourly wind speed (i.e. that averaged over 1 hour) with height above the ground@ with terrain roughness at the site and upwind of the site@ and with probability of occurrence. The purpose of this Item is to give further data from which the expected maximum wind speed averaged over much shorter periods may be estimated from a knowledge of the mean-hourly value. A definition of the expected maximum -second wind speed (commonly known as a gust) is given in Section 3.1. These data are applicable in the estimation of the overall wind loading due to the action of a discrete gust on simple structures. The applicability and limitations of the discrete-gust approach are outlined in Section 2.2. The estimation of gust speeds in this Item is based on a gust factor method which relates a maximum gust speed averaged over t seconds to the corresponding mean-hourly wind speed given by Item No. 82026. The method which is described in the Appendix@ takes into account the following main parameters. (i) The averaging time@ t@ of the maximum gust speed. (ii) The observation or time interval@ To@ in which the maximum gust speed occurs. (iii) The height of the point in question above the ground. (iv) The surface roughness of the local terrain at the site. (v) Changes in terrain roughness upwind of the site. (vi) The probability of the maximum gust speed being exceeded.
ESDU 83045 B-1993 history
1993ESDU 83045 B-1993 STRONG WINDS IN THE ATMOSPHERIC BOUNDARY LAYER