Hi Hans,
By coincidence, I just finished doing the math, recalled from my statics
course some 50 years ago. 1.15 at 30 degrees is indeed the worst-case
factor. It's really a simple calculation, but I'm a bit rusty on this
stuff. I'll share the details, if anyone is interested.
73,
Scott K9MA
On 9/20/2019 23:57, Hans Hammarquist via TowerTalk wrote:
Hi Scott,
I don't have the reference but I did some calculations myself some years ago. I
don't remember the exact numbers but the 1.15 factor is right. If that happens
at 30 degrees or if it was 15 I can't recall, the 1.15 factor is correct.
The explanation is that when the wind attacks the tower 30 degrees off the guy
wire facing the wind, one of the guy wires, on the other side of the tower,
will pull on the tower sidewise and will increase the tension in the wire
facing the wind.
Now, the 15% increase in the guy wire tension isn't that much. You, presumingly
have a much larger safety margin, so an additional 15% should not be the
factor, collapsing the tower.
73 de,
Hans - N2JFS
-----Original Message-----
From: K9MA <k9ma@sdellington.us>
To: towertalk@contesting.com <towertalk@contesting.com>
Sent: Fri, Sep 20, 2019 10:30 pm
Subject: [TowerTalk] Guy Wire Tension Calculation
Does anyone have a reference for calculating worst-case guy wire tension
for a 3-wire system? The only thing I'm unsure of is the effect of wind
direction. One source states that worst case is for wind 30 degrees one
side of a guy, and is 1.15 times the force with the wind aligned with
the guy. The 1.15 factor is easy to calculate, but is that really the
worst case?. It's also clear that, with the wind exactly between two
guys, the tension in each is the same as when the wind is aligned with
one guy. Whether 30 degrees really is the worst case direction seems a
non-trivial calculation.
Note that I'm not asking about calculating the effect of vertical angle,
etc., as that's straight-forward. I'm just interested in the worst case
horizontal component of guy wire tension as a function of wind direction.
73,
Scott K9MA
--
Scott K9MA
k9ma@sdellington.us
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