Alternate Determinations of Wind Design Surface Roughness Factors Using Geographic Information System

The surface roughness of the earth has a significant effect on wind speed. Surface roughness of the earth is defined by the terrain, landscaping and built environment. For decades, structural engineers have been grouping the surface roughness surrounding a site into discrete categories based on the recommendations in The American Society of Civil Engineers Standard 7 (ASCE7), Minimum Design Loads for Buildings and Other Structures. This study presents alternate methods of calculating the roughness factors correlating to the surface roughness surrounding a site using geographic information system (GIS) data and tools. Using GIS, the surface roughness surrounding a structure can be analyzed to refine the roughness factors currently utilized and more precisely define the surface roughness values surrounding a site. This research examines different types of GIS data and multiple methods for determining surface roughness that include methods not traditionally used by wind engineers. These methods offer an alternate approach that account for surface roughness changes and offer to remove the oversimplification of selecting a single exposure to represent what is often more complex terrain. This modeling and analysis is directed toward use in practical design of structures.