> Do not weld the rebar... unless it is ASTM A706 grade or
> you preheat the bars to 300 degrees F for #6 and smaller
> and 500 degrees F for #7 and larger. This is from the
> ANSI/AWS D1.4-98 Structural Welding Code - Reinforcing
> Steel. This code in included in all Building Codes in
> the US by citation.
This is specified in the "Building Code for Requirements for Structural
Concrete (ACI 318-95)." The entire paragraph reads:
3.5.2 -- Welding of reinforcing bars shal conform to "Structural Welding
Code -- Reinforcing Steel," ANSI/AWS D1.4 of the American Welding Society.
Type and location of welded splices and other required welding of
reinforcing bars shall be indicated on the design drawings or in the project
specifications. ASTM reinforcing bar specifications, except for ASTM A 706,
shall be supplemented to require a report of material properties necessary
to conform to the requirements in ANSI/AWS D1.4.
It states a bit more than how to do it. It requires it to be on the
drawings. To me, this means that it has to be signed off on by a PE.
The "Building Code for Requirements for Structural Concrete" (ACI 318-95) is
also a good place to look for other facts on rebar requirements. Section
7.5.4 -- Welding of crossing bars shall not be permitted for assembly of
reinforcement unless authorized by the engineer.
The commentary goes on to say that:
R7.5.4 -- "Tack" welding (welding crossing bars can seriously weaken a bar
at the point welded by creating a metallurical notch effect. This operation
can be performed safely only when the material welded and welding operations
are under continuous competent control, as in the manufacture of welded wire
A disclaimer or two. ACI 318-95 has been superceded. One should probably
read the current code rather than rely on the info I've provided. It
probably hasn't changed, but it would be good to check. Also, one should
check with the local authorities on which codes apply. The ACI and other
codes are only the law if they have been adopted by local authority. It is
possible that other codes are used.