[TowerTalk] Adding guys to self supporting towers

[K7LXC at aol.com]

>  The topic of adding guys to self supporting towers has  been
discussed a number of times on this reflector, but I am
still not  clear on exactly why it supposedly won't work.
If I have figured crrectly,  the worse case compressive load
on a leg at the bottom of a trianguler  tower
is equal to the product of the horizontal windloading
at the top  times the factor h/[w*sqrt(3)] where h is
the height and w is the width of a  face.


>  It seems to me the guyed tower is much stronger and  could
handle a considerably larger wind load based on this
simple  analysis.

>  Comments?
 
    First, I'm not an engineer so these comments are  semi-educated ones. 
Second, the capacity of a tower is limited by the leg  strength so you don't 
want to add unnecessary downward compressive force on  the legs; e.g. guying 
a free standing tower.
 
    BUT IMO if the guys have little or no tension on  them, then they don't 
add appreciably to the compression on the legs but some of  the wind forces 
are transferred from the legs to the guy wires which is the  purpose of the 
guys. Guys in this case are more tethers than guys; that is, they  limit 
the forces on the legs without adding much to the total leg load.  Since a 
self supporting tower doesn't require guy wires, adding them in the  above 
scenario is more like a belt-and-suspenders approach with some added tower  
safety margin. 
 
    A possible problem is that with a bunch of slack in  the guy wires they 
will tend to wind-slam when the wind gusts. That's why you  want a minimum 
of initial tension.
 
Cheers,
Steve       K7LXC
TOWER TECH -
Professional tower services for amateurs