Daniel Moriarty

Deflection caused by wind load

Discussion created by Daniel Moriarty on Aug 6, 2020
Latest reply on Aug 10, 2020 by Bill McEachern

Hello all,

I am working on a static wind load study and am running into a few problems. The antenna shown below is experiencing wind speeds of 135 mph, and a cumulative corresponding normal force (perpendicular to the white radomes) of 270 lbf. To greatly simplify the FEA for my simulation, I eliminated all components hanging off the antenna pole and applied the full wind load experienced by the whole structure directly onto the exposed face of the antenna, with fixed geometry restraints as the sole restraint on the antenna.

The maximum deflection experienced should be around 13”, but I am getting over 49” as my number (which is entirely unreasonable, as the total length of the antenna is only 178”).

To attempt to summarize my main questions:

- Does the fixed geometry at the bottom of the pipe (at the red line marked on the last picture) accurately represent the constraint applied by the mount? If not, what restraint would I use instead?

- Obviously my simplification is extreme, but if the sole concern of the analysis is to determine total deflection of the antenna is my load application acceptable?

Any help with this problem would be greatly appreciated. Let me know if you need more information.





EDIT: Here are some more pictures and information.

Pic 1: Full model - would it be possible to run the wind study on this whole assembly? Tried it one time and ran into mesh problems, in addition to massive load times. I (clearly) do not have a ton of experience with simulation.

Pic 2: Existing FEA study on simplified model (reduced to 1.9" ID, 1.61" ID, 178" long pipe) 

Pic 3: Blue highlighted surfaces were fixed at the bottom of the pipe for FEA study shown in top right.

Pic 4: Split line added along middle of pipe. Force added along left blue surface of pipe

Let me know if any other images would be helpful.