Welding Rebar

[fasboater]

per the ACI318-05 7.5.4 welding of rebar is typically not permitted for crossing bars although it does make reference in section 3.5.2 to AWS D1.4. I do not have this code in my library can anyone tell me what this code specs for welding of rebar for crossing bars only?

Thanks

 

[henri2]

Welding of bars which cross shall not be permitted unless authorized by the Engineer...AWS D1.4-98, Section 4.2.5

 

[csd72]

Why would you want to weld crossed bars?

 

[fasboater]

CSD72

I would choose not to, customer is insisting. It looks like it is fround upon but I have nothing to substantiate this. The only thing IBC, ACI point to in the code is the fact that it is not permitted unless authorized by the engineer. I am really getting pushed because most of our other competitors are giving the OK to do this.

 

[civilperson]

Welding of rebar is done ALL the time with correct procedures,i.e. Cross bars on corbels, development by mechanical means, etc. Write a good spec and be happy!

 

[shin25]

I believe there is a minimum equivalent carbon content requirement for detemining the type of welding. There is also minimum preheat requirement.

 

[UcfSE]

If you are welding rebar, you need to specify ASTM A706 bars instead of A615 bars. A615 does not have controls on material content and equivalent carbon content such that welding is reliable; the bars may develop cracks at the welds. If the customer is not using A706 bars, the answer is pretty clear.

 

[csd72]

Seems like an unnecessary expense if you ask me.

In large bars it could cause secondary stresses that are undesirable.

I would ask them why they want them welded and then propose and appropriate alternative.

csd

 

[civilperson]

A615 bars can be successfully welded with the preheat and correct stick material as stated by shin25. A706 can be welded without the preheat and using almost any weld material.

 

[cessna98j]

I was under the impression that when welding A706 bars, E90xx welding electrodes had to be used. Is this not the case?

 

[JStephen]

I have had people ask me if rebar could be welded simply because they felt it was easier and more secure than tying. If it's A615 material, you just don't know what happens to longitudinal strength when they weld the cross bars.

 

[hokie66]

I think tack welding of small bars like ties to large bars is the problem. Causes stress riser in the large bar. And the "welders" who do this type welding are often not qualified welders and do not use proper procedures.

 

[archeng59]

crossing bars are tied together every day. why would a weld be more secure than a well tied piece of tie wire?

 

[civilperson]

Welding of crossing bar to a rebar needing development of full strength is shown in ACI 318-05 page 176 and 177. The anchor bar is welded to each of the primary reinforcement full strength of the primary steel near the bearing location. WWF can use only one rectangle lap for full splice development because of the welded cross strands.

 

[csd72]

Have a read of this web blog. I particularly like the comment regarding the 'metalurgical notch effect' which was what I was trying to get at above.

http://www.k1ttt.net/technote/welding.html

csd

 

[hokie66]

Good find, csd72. Sometimes web blogs are rubbish, but I believe the information in this one is on the point.