Welding Rebar

[Deadblow]

Hello All,

I plan to use 40'-0" long #5 rebar hairpins, embedded into a 6" concrete slab-on-grade, to resist the horizontal forces at the bottoms of the columns of a pre-engineered metal building. I would like to weld these hairpins to the base plates of the columns. What is an acceptable weldable rebar to specify? I know this may be an elementary question, but is "regular" grade 60 rebar considered weldable?

Thanks!

EIT

 

[mike20793]

You need to specify ASTM A706 Gr 60 instead of ASTM A615 Gr 60 and the welding procedures are from AWS D1.4.

 

[MrHershey]

It's preferable to specify A706, but it's 100% possible to weld A615 steel. Just have to follow the rules with regards to preheat based on CE.

 

[Deadblow]

Ok, thanks for the quick responses! MrHershey, forgive my ignorance, but what exactly is "CE"?

EIT

 

[KootK]

CE = Carbon Equivalemt. Decent article here: Link

I like to debate structural engineering theory -- a lot. If I challenge you on something, know that I'm doing so because I respect your opinion enough to either change it or adopt it.

 

[msquared48]

Why weld them?

Just hook the hairpin behind the anchor bolts, and in the center of the slab.

Mike McCann, PE, SE (WA)

 

[haynewp]

40 ft long hairpins??

 

[RHTPE]

In concept I agree with Mike. However I see some potential difficulties with that approach.

- The foundation wall & column pier/pilaster will likely be constructed in advance of the slab on grade.
- The pier/pilaster will be cast up to the bottom of the grout under the PEMB frame's columns (usual situation in my experience).
- This would require that your hairpins be installed prior to casting the foundation wall & piers/pilasters. It ain't gonna happen because they will have to penetrate the concrete forms AND given their length will interfere with base compaction for the slab on grade.

I would recommend a U-shaped dowel bar sub (Dayton D104A) cast into the pier/pilaster. The dowel-in (Dayton D101) should be long enough to develop the required lap splice length for your #5 tie bars. Then lap-splice your #5 tie bars to the dowel-ins. The dowel-ins & tie bars can be installed after all slab on grade prep is complete.

If the slab on grade placement over-pours the foundation wall & pier/pilaster, then Mike's suggestion would be doable. Just keep in mind that your frame's anchor bolts will now be embedded in 2 separate concrete placements.

Depending on the size of the PEMB frames, the slab on grade may have to wait until the frame is erected so that a crane can be situated inside the building's footprint.

I would also thicken the slab on grade at the tie bar locations to keep the bars below the slab reinforcing yet still insure that there is adequate concrete cover below the bars.



Ralph
Structures Consulting
Northeast USA