I pretty much agree with these comments. There seems to be a perception
among some folks that a welded rebar cage is stronger than a tied one.
I don't believe that to be necessarily true, and about the only
advantage I can think of for a welded cage is that it would hold
together better if it was built somewhere else and moved to the hole.
For assembly on site, the use of hooks and properly overlapped/tied
joints (the 20 times thickness mentioned below) meets every code that
I'm aware of and correlate with the physical mechanisms involved. Given
the varied and uncertain metallurgy of common rebar (weld-rated rebar is
considerably more expensive) I can imagine more jeopardy from welding
the cage than benefit.
Tying is trivially easy anyway. I can make a secure tie in less than
five seconds using the wire ties that have the loops on the end and the
cheap tool with the rotating hook.
73,
Dave AB7E
On 4/12/2014 10:47 PM, Brian Amos wrote:
If you weld it the rod may rust which will cause the concrete to burst. Not
a fun situation as usually the recommended repair is completely remove the
foundation and replace it. As a foundation engineer I only hear the
failures and what the standard of practice and code say, so maybe it has
worked under the right circumstances. If it has an issue and it was not
built to code the insurance company will not cover you.
Tying rebar is not fun and can be hard work but stout teenage boys will
learn quickly and work for a small portion of what a concrete company would
charge. I usually offer a favorite meal ajdand tgat is ebough. You may
even find some free and experienced help from your ham club. I know
whenever someone in my club needs help with something that falls within my
line of work I am more than willing to lend a hand.
Brian
KF7OVD
On Apr 12, 2014 10:42 PM, "Edwin Karl" <edk0kl@centurytel.net> wrote:
Roger,
As part of my mis-spent youth I was an iron worker, worked at it for about
6 years.
We were referred to as "rod busters" by some. In any event installed lots
of iron
in the new York area.
Now that I'm retired, I built my own home, not with my hands, but was the
general
contractor. You can do that in the country ... I did do the reinforcing
myself; so my
driveway, sidewalks, patio, basement walls and floor all have steel
internally. The
also barn has a reinforced concrete floor.
The tower is an AN Wireless 90 footer with a big foundation, rear 3
layers, top bottom
and middle is about 12 feet deep, took 21 yards of concrete to fill the
hole. There is a
section of tower made to go in the foundation which splices to the rear.
Now I'm saying all this because of a decision I made years ago, if I had
the chance, this is
how I would choose to build my own home, etc. It might be nit picking but
the issue with me
probably pertains more to structural iron, like the tower etc. Don't do
anything like welding
which may change the characteristics of the iron negatively. Also affects
galvanizing etc.
Probably way over thinking the issue, which I usually do.
I also will confess in my day, except where cad welding 1 1/4 rear for
power houses etc,
never saw rear welded. Generally a splice is 20 times the diameter side by
side and double
tied.Compared to structural, rear is soft, we would bend it on site for
hooks and angles, so I
suspect it's already not too stuff. But as I said initially the bar
reinforces the concrete, which
holds the bar in place.
Sorry for being so lengthy ... but, if there are other issues as you
mention than explain why welding
might be acceptable. We would take columns and beams using wire to kind of
guy it internally, if
the item has a long way to go or was a difficult pick for the crane etc.
If you are having the job
fabricated off site it probably could be done either way, if you're alone
tack welding could work.
I wish you well, and would appreciate hearing from you as the project
progresses.
By the way, 8 or 9 inch lineman's pliers and end cutting nippers are tools
of the trade, The nippers
work real well when tightening the connection, After a few mistakes, you
can get the hang of it.
Very 73!
ed K0KL
On 4/12/2014 9:37 PM, Roger (K8RI) on TT wrote:
On 1/5/2014 12:58 AM, Roger (K8RI) on TT wrote:
On 1/4/2014 4:01 PM, Ed K0KL wrote:
I can't stand it any longer ...
And the problem is?
If wired in place or near the hole they work fine. If shipped, or handled
a lot they seem to come already welded.
As I only have one useful hand, tack welding is faster, easier, and makes
for a far more secure joint than wiring one with just one hand.
I noted when at my steel supplier, they had a cage, mostly done that was
all welded. The customer would put it on a trailer, haul it 10 miles or so
and then stick it in the hole with the same dimensions as when he picked it
up.
73
Roger (K8RI)
Wire ties are fine to keep the rebar touching from bar to band (the
smaller rod surrounding the
verticals or horizontals as it were). It has been used for years on
buildings, roadways, etc. Generally
speaking the concrete holds the connection together, the connection and
rod make the concrete
strong ...
Order towers with the rebar cage and they likely will come welded and
not tied.
That's been the local experience.
73
Roger (K8RI)
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