CAUTION – THIS POST IS NOT INTENDED TO BE AN AUTHORITATIVE PROCEDURE OR INFORMATION SOURCE ON WIND LOADING CALCULATIONS OR THE SAFETY OF YOUR INTENDED TOWER AND ANTENNA SYSTEM DESIGN. USE THE INFORMATION HERE AT YOUR OWN RISK AND CONSULT A PROFESSIONAL ENGINEER AS THE FINAL WORD ON WHETHER YOUR TOWER DESIGN AND PLANS ARE SAFE. FAILURE TO PERFORM THESE STEPS CORRECTLY CAN LEAD TO MAJOR DAMAGE OR FAILURE AND COLLAPSE OF YOUR TOWER AND COULD RESULT IN SEVERE PROPERTY DAMAGE, INJURY AND/OR DEATH! Now that we have the cautions out-of-the-way, I should note that the most important aspect of engineering a tower and antenna system is to ensure that the tower is not overloaded and is safe in the wind (and icing) conditions that may be encountered. The ARRL Antenna Book chapter 26, Appendix A is a source on how to perform a basic form of these calculations. You should also read and understand Rohn’s brief on TIA-222 Rev G before beginning. IN ALL CASES, SEEK THE HELP OF A PROFESSIONAL ENGINEER OR EQUIVALENT SKILLED TOWER PROFESSIONAL TO ENSURE THAT YOUR TOWER DESIGN AND PLANS ARE SAFE.
I will not try to repeat the procedure for performing the wind loading calculations here. I do think its important to note the following (all of this is covered in the ARRL Antenna Book):
- Make sure you select a maximum wind speed target that properly accounts for your location and exposure (how much the tower site will be exposed to the wind)
- You should do a set of calculations for both ice and non-ice conditions if your location has the potential to experience icing in the winter. Note that icing significantly increases the size and weight of anything that it builds upon and therefore the wind and other loads on your tower!
- You need to account for all equipment that has a wind profile on your tower. This includes antennas, feedlines, masts, rotators, electronics enclosures, etc. that will be mounted on your tower. The elements beyond the antennas themselves can easily add up to be a big part of the overall wind load.
- Do not exceed the manufacturer’s specifications for wind loads for your planned tower height, guying arrangement, exposure, etc. All of Rohn’s specifications include this information. DO NOT OVERLOAD YOUR TOWER BY EXCEEDING THE MANUFACTURER’S SPECIFICATIONS.
These calculations are best done by an experienced engineer or tower professional. There are significant variations in the way various manufacturers quote their wind loading specifications so it is best to seek the help of a profession with these steps.
USE THE INFORMATION IN THIS POST AT YOUR OWN RISK! THE AUTHOR ACCEPTS NO RESPONSIBILITY FOR THE CORRECTNESS, USE OR ANY DAMAGES, CONSEQUENCES, OR LOSSES ASSOCIATED WITH THE USE OF THE INFORMATION IN THIS POST.
– Fred (AB1OC)