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Interpretation of shielding in TIA 222-G

Interpretation of shielding in TIA 222-G

(OP)
I'm having a disagreement with another engineer about the interpretation of this standard's definition of shielding (Section 2.6.9.4 of TIA 222-G, and Figure 2-11).

His contention is that coax cables strapped to a smooth round pole structure would be classified as completely shielded when the wind direction is coming from the opposite side of the pole, and that the cables would be treated a cluster mount (Fig 2-12) with the wind direction 90 degrees to that.

My argument is that a smooth round pole acts as an airfoil under high wind and that the cables would produce a considerable drag regardless of their placement on the pole or the wind direction. However, I can't seem to find any published justification for this view other than the reference in ASCE 7-02 under Other Stuctures, Fig 6-19 which defines force coefficients of different shapes and h/D ratios. This section shows an increased drag coefficient depending on the roughness of the pole's surface varying as a function of the protruding elements (i.e., the coax cable) and the pole's diameter at a given level.

Can anyone provide me with another reference that might support this claim, or am I simply looking at this application too conservatively? Does the TIA standard really mean to define a cable strapped to a pole as completely shielded from the wind in one direction?

Any enlightenment on this would be appreciated.




 

http://www.spiraleng.com
 

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