[TowerTalk] what is 'circular tie' as is used in a towers concrete base?

[Roger (K8RI) on TT]

My opinion:
Typically the rebar only adds strength to the concrete base.  IOW, You 
don't need as large a base, or as strong a mix when rebar is used.  If 
you were "positive" the base could maintain structural integrity under 
any conditions you wouldn't need rebar.

Regardless of whether welded or tied, The rebar normally doesn't need a 
rigid connections.  The ties only keep the rebar in place during the pour.

If you don't need precision and are not making sharp bends in big stuff 
you might be able to do the bending with a manual conduit bender.   
Welding just makes building a rugged cage that can stand rough handling 
easier.  Just be sure to use rebar made for welding.  Welds on the 
normal stuff are quite fragile.

Bending rod, rerod, pipe, etc...into a circle is usually done with three 
rollers.  The rollers  (Which usually have a radius cut into them to 
keep the rod centered) are mounted in a triangular shape with the bottom 
of the center one slightly below the tops of the outside rollers  (The 
height of this roller is adjustable).  To bend much of anything, these 
things can be pretty hefty.  The distance between the rollers is 
surprisingly short.  Having them close reduces, or eliminates waste.

There is a bit of a learning curve, but it's neither steep nor long. A 
rough explanation:  The center roller is raised so the rod can be 
inserted  over the outside rollers and under the center roller. Then the 
center roller is lowered and tension applied. The first pass produces a 
shallow arc. The center roller is lowered for each successive pass which 
tightens the arc eventually into a circle

I've seen the rollers mounted into the top of a steel bench with a 
movable center wheel.  The rollers are powered and a center screw, or 
hydraulic ram powers the movement of the center roller.  With those you 
have to be aware of the thd of tht piece coming back, or you could 
skewer yourself.

73

Roger (K8RI




On 10/20/2015 11:29 AM, StellarCAT wrote:
> Rohn says to use 8 #7 rebar (SERIOUSLY! 7/8”!!) ... and then it shows ‘#4 circular ties 2 1/2” OC with 2” cover with 24” laps’
>
> huh?
>
> I’ve always just dug a hole – usually around 3 x 3 x 3 ... put the tower section in (with temp guys) ... put in a few pieces of 1/2” re bar and been done with it .... but now I have to follow the Rohn specifications which seem onerous at best (I know, I know – guys that say “follow it to the letter”) ... and I’ve no clue what #4 circular tie is. SURELY its not #4 rebar BENT in a circle!?
>
> Googling so far hasn’t shown me anything that helps.
>
> Gary
> K9RX
>
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-- 

73

Roger (K8RI)


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