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Re: [TowerTalk] Adding guys to self supporting towers

To: towertalk <towertalk@contesting.com>
Subject: Re: [TowerTalk] Adding guys to self supporting towers
From: Steve Maki <lists@oakcom.org>
Date: Tue, 13 Aug 2013 21:29:48 -0400
List-post: <towertalk@contesting.com">mailto:towertalk@contesting.com>
On 8/13/2013 10:09 AM, Jim Lux wrote:

On 8/13/13 6:47 AM, Jim Thomson wrote:
##  The stress on the cross bracing is actually reduced when guys are
added to a
free standing tower, not an issue.

How so?

In a no wind static case, the guys add down force, some of which will
appear on the diagonal cross braces.  How much depends on the relative
compression stiffness of the brace vs the verticals.

In the wind loaded case, the guys transform some of the horizontal
bending load into down force.  That could be a wash in terms of loads
but it's hard to tell, depending again on the relative stiffnesses. E.g.
downwind side has less load due to bending, but more load due to guy
induced downforce, but the guy downforce is distributed among all
three/four vertical legs.

I'm having a hard time with this. It seems to me that in the guyed no-wind state, the added force to diagonals from guy tension will be almost nonexistent as long as the guys are tensioned equally. Isn't all of the additional vertical force, well, vertical?

I thought that stress in the diagonals is the result of flexing of the legs, which MUST be most pronounced in the unguyed windy condition???

-Steve K8LX




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