[TowerTalk] Used Tower-Practical Strength Considerations

[Wilson Lamb]

OK, so I dragged in 70' of used tower.  It was a "bargain".
There's some light rust, but nothing structurally significant.
Now to the questions.

Several sections have 1/4 and 5/16" holes.  I'm thinking someone may have 
bored out some to get tighter fits on the bolts.  Also, some sections have 
ratty holes that look wallered out by being loose.  It's hard to visualizr 
this happening, except for a heavily loaded tower with a lot of load, may 
self supporting?
  Is it common?
Have others seen it?
I have no good feel for how much of the bending load gets to the bolts, but 
it seems like the overlappiing joint would take most of it, especially at 
moderate load.  Does anyone have model results or experience with joint 
failures?
I've seen dropped towers with serious bending nut never a joint failure.

Has anyone bored the holes in 25G to 3/8"?
Could the loss of cross section be significant to joint strength?
Has anyone seen bolts fail in shear?
Should one use higher grade bolts, or is the leg material likely to tear 
before the bolts fail?

A couple of braces are detached at one end, although there is no visible 
bending of the legs.  I'm guessing this was caused by some sort of 
mishandling, but don't know.  I'm hoping that a nice MIG weld will be 
sufficient for reattachment??

I'm asking all this to see if there are problems that might bite me.  I 
don't plan to go very high, 60' max, but want to not worry about my friends 
or me climbing for installation and, hopefully in the distant future, 
maintenance.

Thanks for any guidance or experience you can share.

Wilson
W4BOH