[TowerTalk] rebar (was 900 MHz tower)

[Jim Lux]

At 06:43 AM 12/30/2005, K7LXC at aol.com wrote:

> >  However as far as welding goes, rebar CAN be welded, but it  takes a
>special
>technique, and requires some knowledge of the bar material  and the right
>welding rod.  This isn't a "get the old buzz box out and  tack everything
>together" kind of operation.  And, as always with  structural kinds of
>things, you need to talk to your local regulators.
>
>         It's been my experience  that rebar in tower bases isn't usually
>'structural'. It's primary purpose is to  hold the concrete together while it
>cures to prevent cracks in it.


Concrete has no real tension strength, so the rebar provides the needed 
tension strength.  If your tower is a guyed tower with only compression 
loads on the big block o'concrete, you're right, the rebar might not be 
doing much.  However, if you have a free standing tower which transmits 
bending loads to the concrete as tension (on the upwind side) and 
compression (on the downwind side), you'd better have the rebar in there. 
Even on a guyed tower, there are shear loads on the concrete, which, by 
definition, are a combination of tension and compression loads.

Upshot.. rebar is most definitely structural.


>Rebar  schedules are in the drawings for each tower
>so be sure to follow them.
>
>     BTW rebar comes in # sizes; i.e. #4, #6, etc. This  refers to 1/8 inch
>increments. For example, #4 is 4/8ths or 1/2 inch; #6 is  6/8ths or 3/4 inch.
>
>Cheers,
>Steve   K7LXC
>TOWER TECH


Jim