Return to index: [Subject] [Thread] [Date] [Author]

Re: Antenna Dish

[Subject Prev][Subject Next][Thread Prev][Thread Next] Eric:

The suggestions concerning the EIA/TIA code are excellent.  In reading your initial message, I note that the antenna manufacturer calcs are for a service level Mot.  What wind speed is this service level?  And this would suggest that these values are for the antenna aimed at it's target and not in a survival position as it is supposed to be placed prior to an incoming typhoon.

Appendix B of the EIA/TIA code provides coefficients for wind loads on typical microwave antennas/reflectors, but these are for the dish face being vertically orientated.    Review this section and consider using the Cs values for the antenna at 90 degrees from the appropriate Table.  Using the Cm value could also provide a moment - which you could back out an uplift or downward force.  Figure B2 will show you the wind and force directions.


But the ASCE 7-98 mentions this: 

6.5. METHOD 2 - ANALYTICAL PROCEDURE: 

A building or other structure whose design winds loads are determined in accordance with this section shall meet all of the following conditions: 1......... 2.  The building or other structure does not have response characteristics making it subject to across wind loading, vortex shedding, instability due to galloping or flutter; or does not have a site location for which channeling effects or buffeting in the wake of upwind obstructions warrant special consideration."

You could go back to the antenna manufacturer and request that they provide you with the all the forces for the design conditions (180 mph) and you just provide the foundation design.  Let their engineer sign off on that.

You still have to add in the 5' diameter support column plus any other appurtenances on that column (such as cables and ladders).

Try to obtain an Andrew Corporation catalog.   They pretty much set the standards for the tower and antenna industry.


Neil Moore, S.E.
neil moore and associates
shingle springs, ca