Welding rebar to pipe. What size weld, how long? 2

[Josh_Structural_Eng]

Currently I am working on resolving a request for information. We have piles with rebar that hooks into the concrete foundation. In some of these piles the rebar has been broken and cut. My boss would like me to have new rebar welded to the outside of these piles. I am trying to figure out where in the AISC manual I can find an equation to figure out how long the weld will need to be and what size weld I will need. I'm just an intern trying to do a good job. Please help. I have looked through the weld section and I noticed equation (8-2b). Can this be used to figure out the length and weld diameter for welding two round steel objects together? Also, what type of weld would you use for welding a pipe and rebar together?

 

[Ron]

Why do you want to weld a pipe to the rebar? I gather that you want to splice rebar together to restore the length. The criteria for welding rebar are given in AWS D1.4, Structural Welding Code-Reinforcing Steel. Keep in mind that rebar is a relatively poor material for welding and if done, it must be done with care. As for the weld design, you are likely trying to restore the tensile capacity of the rebar through the splice. That puts the weld in shear since this would be a lap splice, not, not a complete penetration butt splice. You can work out the geometry of the shear and the amount of weld you need through a review of the AWS code and I would also suggest that you consult Blodgett's books on weld design.

 

[LittleInch]

a sketch / drawing or picture would help, but it sounds to me like the piles are metal pipes? and the re-bar is attached to them to anchor the slab.

The attachment sounds like an axial fillet weld welding the re-bar to the pipe??

I think we need more info, but also agree - welding re-bar without the right material and welding spec / consumables / preheat is normally a recipe for later disaster. It really doesn't like it.

search "welding rebar" and you find gems like this

http://www.eng-tips.com/viewthread.cfm?qid=55969

Remember - More details = better answers
Also: If you get a response it's polite to respond to it.

 

[Lomarandil]

Any weld to the rebar would be a flare bevel weld, not a fillet. As such, 8-2b doesn't apply. You'll need to get into the requirements in the AISC specification, section J2

Ron and LittleInch are right -- the process will be the critical element here. Probably best to get that figured out first.

 

[Josh_Structural_Eng]

I have attached the detail I am working on, and I have also attached the detail with comments to give you a better idea of what I am trying to do.

Correct the piles are metal pipes and the rebar is attached to anchor the slab. I am trying to restore the tensile capacity of the rebar. I was told that we will be using #8 hooked bars for the new bars that are going to be welded to the pile. I will look into section J2 of the AISC manual. As far as the process goes I am not too sure about that.

 

[sandman21]

AWS D1.4 is the standard you need to use, this will give you the size of the flare bevel weld, you would then use this size in the AISC for the size of the weld. The reinforcing bar should be ASTM A706 to allow for easy welding. The weld and welder will need to be qualified for at least your size of bar.

 

[Josh_Structural_Eng]

Here is the attachment of the of the detail with comments.

 

[JedClampett]

It's difficult to weld reinforcing, unless it's low carbon. But in my old nuclear days, we used to use Cadwelds. Not real cheap, but they solve the problem. Plus you can use them to splice #14 or #18 bars (not the case here). I've seen them welded to steel members with rebars inserted.

 

[wannabeSE]

I would not use AISC to calculate capacity of welds on rebar. AWS D1.4 should be used. AISC results may be similar or close enough, but AWS D1.4 provides the code requirements. For instance, I think the effective weld size for flare v and flare bevel groove welds is a little different for reinforcing.