The purpose of the “Windspeed Website” is to provide users with a site-specific windspeed that are used in the determination of design wind loads for buildings and other structures. On this website, users can obtain windspeeds compatible with ASCE 7-10, ASCE 7-05, and ASCE 7-93. Windspeeds are also provided for serviceability purposes for 10-, 25-, 50-, and 100-year return periods when using ASCE 7-10. Users are cautioned to be sure to use the correct windspeed associated with the edition of ASCE 7 being used in the design. Without providing too much detail, the design windspeeds are different because the basis for wind design was service-level, fastest mile windspeeds in ASCE 7-93, service-level, 3-second gust windspeeds in ASCE 7-05 and strength-level, 3-second gust windspeeds in ASCE 7-10. It is assumed that the users of this site have competency to understand how to calculate and apply design wind loads to structural models of buildings or other structures.
The reason this utility is needed is that the spatial resolution of the windspeed maps that are displayed in ASCE 7 are not sufficient to determine a site specific windspeed. There are no reference city or town locations on the ASCE 7 windspeed maps and while county boundaries are shown, the resolution is affected when the maps are expanded large enough to distinguish the boundaries and approximate the city locations.
Windspeeds are site-specific for the location provided and are found by interpolation of map contours to the nearest 1-mph. Users are cautioned to provide the most accurate location for the building site by specifying either the known street address, city and state or the latitude and longitude to at least five (5) decimal places. If only the name of the city/state or ZIP code is provided, the website will provide windspeed information for the centroid of the city or ZIP code and thus could either over or underestimate the actual design windspeed for the site. An underestimation of windspeed could result is a design that does not meet the requirements for minimum wind design loads for the building under consideration.