In a message dated 98-07-01 09:58:30 EDT, n3rr@erols.com writes:
> Per my 1991 ROHN catalog, for 110 mph basic wind (no ice) your 110 ft of 25G
> isn't even on the charts! 100 ft of 25G @ 110 mph wind requires 80% guying
> and will take only 7.4 sq ft load.
Actually York county is only an 85 MPH windspeed zone but it is within
100 miles of hurricane oceanline so I think that the 110 feet and 8 sq.ft. of
wind loading is reasonable. I don't discourage anyone from over-enginering
their installation.
An obviously better steel choice is Rohn 45G. A much better investment
for this scenario.
>
> Even the 90 mph wind no ice 110 ft of 25G tower specs out at 80% guying.
>
> Your 45.5% (50/110) guying design is way too low and will result in a very
> unstable installation (my opinion). For example, I use 93% in my design.
> The higher the % guying, the more stable the design. I've heard that the
> rule
> of thumb is no less than 60% guying.
Yes, 80% for guy anchors is ONE scenario. Pirod Towers uses 70% for
their specs. Yes, 93% does reduce some of the system stresses. But many things
are possible IF you get an engineer involved to design and calc everything.
The 45% guying is highly suspect without the aforementioned professional
intervention. DO NOT hip-pocket engineer something like this.
Cheers, Steve K7LXC
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