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## Re: [TowerTalk] Windloading - Chrome-moly VS: steel

 To: kb0fhp@comcast.net, Mike Re: [TowerTalk] Windloading - Chrome-moly VS: steel Jim Lux Fri, 14 Jul 2006 10:43:55 -0700
 ```At 07:46 AM 7/14/2006, kb0fhp@comcast.net wrote: >Now for a 20 foot mast, the max load (located at the tippy-top of the >mast) is about 2850 pounds for the 4130, and about 1700 pounds for the >black steel A53 Shedule 80 pipe. If I use a safety factor of 2 - which I >don't think is unreasonable, then the maximum loads are about 1425 pounds >for AISI 4130, and about 850 pounds for the A53 Steel pipe. > >This is where I need help. Now assuming the codes, how do I calculate the >windloading?. I know there was a long discussion on that a while ago - >which I need to review. I really wish there was a chart - antenna loading >in ft^2 vs wind speed...... Loading(Lbs/sqft) = windspeed (mi/hr)^2/391 ( 391 takes into account all the unit conversions and the air density at sea level standard conditions) 60 mi/hr = 9.2 lb/sf 70 mi/hr = 12.5 lb/sf 80 16.4 90 20.7 100 25.6 Actually, for rough and ready back of the envelope estimates, I use (mi/hr)^2/400, so 20 mi/hr = 1 lb/sf, and then scale from there, since load goes as the square of speed.. 40 mi/hr = 4, 60 mi/hr = 9, 80->16, 100->25, etc. >.Does someone know of such a beast? SInce the worst case is a point load >at the end of the mast - this could really help size the necessary mast sizes. Don't neglect the drag on the mast itself. cross sectional area of mast, load at half way up the mast. >As with all calculations, it is best to verify the calculations, and if >necessary contact the appropriate engineering or other cognizant authority..... All a matter of risk posture. Back of the envelope, double the numbers, put it up and hope it doesn't fall on anything important is just as valid as a finite element model with 0.1" grid cells and statistical wind models. "Analysis paralysis" is an ever present hazard. Jim _______________________________________________ _______________________________________________ TowerTalk mailing list TowerTalk@contesting.com http://lists.contesting.com/mailman/listinfo/towertalk ```
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