Hi folks.  New to the forum.

Is anyone aware of a reference standard for "shop repair" arc welding of welded wire reinforcement sheets?  If there is no reference standard (which based on what I can find, is the likely response), then does anyone have any personal experience with this issue they could share?  Said WWR sheets would be used as tensile reinforcement in structural concrete.  Assume scrapping the WWR in favor of new sheets is not an option.

ASTM A1064 Section 6.2 is pretty explicit in stating "Longitudinal and transverse wires shall be securely connected at every intersection by a process of electrical resistance welding which employs the principle of fusion combined with pressure", but this should come as no surprise given it's the standard specification for welded wire. 

Where the "door is left open" is via commentary section R3.5.2 in ACI 318 that states:

"Welding of wire to wire... is not covered by AWS D1.4.  If welding of this type is required on a project, the contract documents should specify requirements of performance criteria for this welding.  If cold drawn wires are to be welded, the welding procedures should address the potential loss of yield strength and ductility achieved by the cold-working process (during manufacture) when such wires are heated by welding.  These potential concerns are not an issue for machine or resistance welding as used in the manufacture of welded plain and deformed wire reinforcement covered by ASTM A1064."

So in that statement, my focus immediately goes to "...should specify requirements of performance criteria for this welding."  If there is no published basis on which to develop performance criteria, then is it safe to assume that the only recourse is for the shop itself to develop performance criteria through testing of its own (a custom PQR, if you will)? 

Thanks for your time!

I'm not claiming to be an expert on this particular subject, so take my opinion for what it is worth.

Welded wire fabric doesn't depend on the strength of the weld between the "wires" to develop "strength." Wire fabric is usually used for crack control. That is, it is intended to prevent cracks in concrete decks, sidewalks, etc. In reality, the welds are intended to hold the wires in position while the concrete is placed. When the concrete is reinforced to develop strength, i.e., the steel transfers tensile loads and the concrete the compressive loads, concrete reinforcing bars are used.

Concrete reinforcing bars are wired together for the purpose of holding the rods in place until the concrete is placed. The ties have to be secure enough to keep the bars from being displaced while the forms are erected and the concrete placed and vibrated. The strength is a function of the rebar strength and the bond developed between the concrete and deformation of the bars, i.e., the interaction is dependent on the mechanical interaction of the deformed bars and the concrete. 

Now, back to the original question and why is there a concern for welding the wire mats? Are you simply repairing welds that broke or for some other purpose?

Al