TIA-222 wind load on appurtenance (cables) 1

[osw]

Hello - I am following the TIA-222 on calculating the wind loads on cables mounted on stand-offs (two cables/stand for a total of 6 pairs) on the outside of an antenna mast. While Section 2.6.9.2 provides information on how to compute the EPA - effective projected area of the appurtenance (cables in this case) I am using the projected area of the two cables normal to wind. My question is, for a group of cables as shown, is total wind force (lb/ft) equal to the sum of the forces on each of the pairs or use a reduced number assuming some shielding effects due to proximity and orientation of the cables.
Thank you,

 

[r13]

I don't have any experience on your application, but to suggest to follow the guide/standard exactly as its telling. If shielding effect is not addressed by the guide/standard, then it dies not apply, unless there is testing been done, and proven correct otherwise.

 

[holttho]

If you are doing analysis per TIA-222 Rev G or Rev H, then you can apply shielding to grouped clusters of feedline cables. (Shielding is outlined in 2.6.11.4) Rev F does not allow for this, however, there isn't any reason anyone should be doing anything in Rev F anymore. Shielding is may be considered for elements so long as they are within 2.0 times the projected area of the largest element. That is to say, if your first feedline bundle is 4" in diameter, then you can consider the neighboring second bundle to be fully shielded if it is within 8" in that direction. (bundle 1 is the larger in this scenario) Keep in mind, this may not hold as you look at the bundles from different directions. North-south may be shielded, but east-west may not. As you leave that 2.0 boundary, the shielding value goes down linearly, however, in practice, it is simpler and more conservative to just go from full to nothing at that limit.

Generally with feedline bundles, they are rarely nice and symmetric and are very hard to calculate every possible orientation at every location, so a fair amount of engineering judgment and caution is required.