Force Coefficients (Ca) for Appurtenances

[ClintS]

I am working on an analysis of a flagpole tower that conceals antennas. The concealment portion of the tower is 50' long and 30" diam. My plan is to treat this section as an appurtenance for loading purposes. If I use the entire length/diam, the aspect ratio is 20. However, the original design of the pole broke the 50' concealment cylinder into (10) 5' sections, which reduces the aspect ratio to 2. Using Table 3 of TIA/EIA-222-F, the Force Coefficient will be either 1.08 for an aspect ratio of 20 or .8 for the aspect ratio of 2. This is a significant difference. My questions are: Which should I use? and Why is it that the larger the aspect ratio, the larger the Force Coefficient?

 

[ATSE]

Use the larger coefficient. That is the actual physical condition.
The effective wind loading on the pole has nothing to do with design segments and how you analyze the pole.