welding rebar

[Redeemd]

We typically have not called out weld size for welding rebar perpendicular to a steel plate (e.g. embed plate); instead we've always referenced AWS D1.4.

Recently, a steel fabricator sent thru a change order because he had to increase the weld size per our marked-up shop drawings. Researching this, we found that AWS D1.4 does not show weld sizes required to develop the strength of the bar, much to our surprise.

Should a fabricator know what weld size to use to weld a rebar to develop the strength of the bar? We've never had trouble with this before. Looking for a valid defense...

 

[TDAA]

Did he supply the shop drawings for you to review? How did he get the size then? Why no RFI at the time of the shop drawing?

 

[Redeemd]

His lame excuse was that he relied on the minimum weld size called for in AISC. We told him that AISC doesn't cover welding of rebar, but since AWS D1.4 doesn't cover weld size either we didn't have anything to back up our position.

 

[Redeemd]

Yes - he did submit shop drawings for our review.
No - RFI was not sent.

 

[RacingAZ]

It's in the PCI Design Handbook.

Do you have any kind of wording in your plans that say "welded rebars are required to develop their full strength (or 125%)", or words to that effect?

Your mistake is red lining the shops with the actual weld size when your CD's don't show any. You've given the fabricator ammunition to claim a discrepancy or deviation from the contract documents.

That's why I always call out the size for welding rebars in steel plates or insert a typical detail to cover the weld sizes.

 

[RHTPE]

As an engineer involved in concrete construction (from the supplier/contractor side), my minimum expection would be at least a note on your detail requiring that the weld develop 100% of the bar's yield strengh. Typical rebar in the US meets ASTM A615, and is not readily weldable without special procedures. If those procedures are not followed, the bars become very brittle. Thus the existance of AWS D1.4. Rebar meeting ASTM A706 is weldable, and really should be specified for an application such as this.

Aside from the above, expecting a structural steel detailer to know the bar strengths might be a stretch, but the question should have been raised. As the Engineer of Record you should know the content of the documents that you reference and fill in the missing/required information not contained in that document. Now you know what D1.4 doesn't cover and you'll be able to provide better details on future work. Does any other AWS document specify the required weld size for a connection?

Just my NTBH opinion.


Ralph
Structures Consulting
Northeast USA

 

[TDAA]

Most contracts I have worked with require the contractor to notify the engineer if there is a problem, and get clarification, prior to performing the work. This is often treated "flexibly" to allow projects to move on.

If he knew your spec did not address the welds, he should have asked. He instead assumed something different for pricing (and built that way?), and now expects that there should be a change?

Lets see, he is the one that apparently felt the need to change the weld size, based on how I read your post. That would indicate that he did know what it should be, or had no clue what he bid on in the first place. Not quite right either way.

Personally, I think you are down to a contract issue, and did they follow the contract procedures outlined to address a discrepancy in the plans. These fights suck though. How it gets handled has a lot to do with the contract, owner, contractor, and your firm.

 

[hokie66]

Why does weld size come into it? Don't you folks butt well bars to plates?

 

[RHTPE]

hokie,

The typical assembly is usually square-cut bar ends, with the bar perpendicular to the plate, then a full-circumference fillet weld used to join them.

Ralph
Structures Consulting
Northeast USA

 

[hokie66]

Ralph,

I gathered as much. We typically use full penetration welds for these in Australia.

 

[Lion06]

I used to call for the bar to be ground to a chisel point and provide groove welds, but I was told that is too expensive and to provide fillet welds all around per PCI.

 

[hokie66]

Why would you use a recommendation of a prestressed concrete body for designing welds? Surely a steel fabricator can't be expected to know that.

 

[Lion06]

I don't think it's a recommendation, it's just a table that shows what fillet weld is required to fully develop the bars. It gives the sizes for different grades of steel, and different electrodes.

I don't refer to those tables on the drawings. I call out the weld size, but I do reference the tables to determine the weld size. I never show a fillet weld symbol with no size unless it's a generic connection that is to be designed by others.