Wind Load Factor Analysis: An Exploratory Approach Snohomish Wind Group Alexi Curelop, Kofi Petty,...
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![Page 1: Wind Load Factor Analysis: An Exploratory Approach Snohomish Wind Group Alexi Curelop, Kofi Petty, Sonya Prasertong Geography 469 Spring 2010.](https://reader035.fdocuments.net/reader035/viewer/2022062309/56649d435503460f94a1ff32/html5/thumbnails/1.jpg)
Wind Load Factor Analysis: An Exploratory Approach
Snohomish Wind GroupAlexi Curelop, Kofi Petty, Sonya Prasertong
Geography 469Spring 2010
![Page 2: Wind Load Factor Analysis: An Exploratory Approach Snohomish Wind Group Alexi Curelop, Kofi Petty, Sonya Prasertong Geography 469 Spring 2010.](https://reader035.fdocuments.net/reader035/viewer/2022062309/56649d435503460f94a1ff32/html5/thumbnails/2.jpg)
Goal and Purpose
• How can we calculate and visualize the wind velocity pressure constant (Kzt factor) using the topography of Snohomish County?
• Scott Beard, Plans Examiner for City of Tacoma, manually produced Kzt factors for King County and City of Tacoma
• Will Rugg, GIS Analyst for Snohomish County Planning and Development Services, interested in how to automate the process via ArcGIS
• Our group decided to take on this topic in order to challenge our knowledge of how to apply GIS to real world problems
![Page 3: Wind Load Factor Analysis: An Exploratory Approach Snohomish Wind Group Alexi Curelop, Kofi Petty, Sonya Prasertong Geography 469 Spring 2010.](https://reader035.fdocuments.net/reader035/viewer/2022062309/56649d435503460f94a1ff32/html5/thumbnails/3.jpg)
Kzt Factor Significance
• Kzt factor when calculated is equivalent to specified wind speeds and is on a scale of 1-2 (eg. Kzt of 2 = 120mph)
• It is part of a larger calculation used by planners and architects for determining appropriate areas and materials when developing land
• Our project, if successful, could aid Snohomish County in reducing the costs of building and planning for their architects and planners
![Page 4: Wind Load Factor Analysis: An Exploratory Approach Snohomish Wind Group Alexi Curelop, Kofi Petty, Sonya Prasertong Geography 469 Spring 2010.](https://reader035.fdocuments.net/reader035/viewer/2022062309/56649d435503460f94a1ff32/html5/thumbnails/4.jpg)
The Kzt Factor
• Kzt = (1 + K1 + K2 + K3)2
• K 1 = determined from table below
• K2 = (1 – (|x|/µLh))
• K3= e-γz/Lh
Parameters for Speed-Up over Hills and Escarpments
Hill Shape
Exposure
γµ
B C D Upwind of Crest Downwind of Crest
2-dimensional ridges
1.30
1.45 1.55 3 1.5 1.5
2-dimensional escarpments
0.75
0.85 0.95 2.5 1.5 4
3-dimensional axisym, hill
0.95
1.05 1.15 4 1.5 1.5
Source: American Society of Civil Engineers: Minimum Design Loads for Buildings and Other Structures, 2006
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Need-to-Know Questions
1. What are the mid-points of the data?
2. Based off of the mid-points, what is the velocity pressure constant (Kzt factor) of the terrain?
3. How do we model the output information product?
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![Page 7: Wind Load Factor Analysis: An Exploratory Approach Snohomish Wind Group Alexi Curelop, Kofi Petty, Sonya Prasertong Geography 469 Spring 2010.](https://reader035.fdocuments.net/reader035/viewer/2022062309/56649d435503460f94a1ff32/html5/thumbnails/7.jpg)
1. What are the mid-points of the data?
• Using primarily Spatial Analyst, we were able to calculate the slope of our pilot area to identify base and peak elevations of landforms
• We could then create a map of depicting polygons representing these areas, with the centroids for each polygon identified
• Tools used: Slope Calculation, Raster Calculator, Convert Raster to Features, Neighborhood Statistics, Zonal Statistics
![Page 8: Wind Load Factor Analysis: An Exploratory Approach Snohomish Wind Group Alexi Curelop, Kofi Petty, Sonya Prasertong Geography 469 Spring 2010.](https://reader035.fdocuments.net/reader035/viewer/2022062309/56649d435503460f94a1ff32/html5/thumbnails/8.jpg)
![Page 9: Wind Load Factor Analysis: An Exploratory Approach Snohomish Wind Group Alexi Curelop, Kofi Petty, Sonya Prasertong Geography 469 Spring 2010.](https://reader035.fdocuments.net/reader035/viewer/2022062309/56649d435503460f94a1ff32/html5/thumbnails/9.jpg)
2. Based off of the mid-points, what is the velocity pressure constant (Kzt factor) of the
terrain?
• From here we used the Identify tool to find the exact elevations for the the base and peak polygons of our landforms
• We created lines and points to keep track of our calculations, which were recorded in an Excel spreadsheet
• Due to the specifications of the Kzt formula, only 4 landforms were able to be selected for calculation
• Tools used: Identify tool, Measurement tool, Editor toolbar, Microsoft Excel
![Page 10: Wind Load Factor Analysis: An Exploratory Approach Snohomish Wind Group Alexi Curelop, Kofi Petty, Sonya Prasertong Geography 469 Spring 2010.](https://reader035.fdocuments.net/reader035/viewer/2022062309/56649d435503460f94a1ff32/html5/thumbnails/10.jpg)
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3. How do we model the output information product?
• We decided the best method of visualization would be colored polygons around our selected landforms, with each color representing a range of Kzt
• We decided to use the Waterbodies and Major Roads layers as a means of orienting the audience to our pilot area location
• Tools used: Editor toolbar, Add Field tool, Transparency setting
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Analysis/Process
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Findings
• Due to the specifications of what landforms can be calculated for Kzt, there were only 4 landforms that could be selected
• Of these 4 landforms, each seemed to fall on the two extremes of the Kzt factor scale (either 1 or very close to 2).
• Kzt Factor Results:Landform A = 2.43Landform B = 1.99Landform C = 1.00Landform D = 1.93
![Page 15: Wind Load Factor Analysis: An Exploratory Approach Snohomish Wind Group Alexi Curelop, Kofi Petty, Sonya Prasertong Geography 469 Spring 2010.](https://reader035.fdocuments.net/reader035/viewer/2022062309/56649d435503460f94a1ff32/html5/thumbnails/15.jpg)
Conclusions
• The area we selected contained landforms on both extremes of the Kzt factor scale of 1-2
• We were able to automate the process of calculating peak and base elevations
• More time is needed in order to create a more complex pilot study
• Python scripting could assist in automating our manual Kzt calculations
• Due to our lack of comprehensive knowledge of the particulars of civil engineering formulas, errors in calculations were a possibility
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Recommendations
• Creating a Python script that can automatically run the manual calculations we performed
• Work with individuals that have an in-depth knowledge of both the capabilities of GIS as well as civil engineering background to limit possible errors in calculations
• Allow for a study with a longer timeline