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RE: Welding Rebar

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As Harold pointed out, welding crossing bars together essentially means
tack-welding them, which is at best a quality control problem and at
worst a crack creation process.  This is stated in the commentary for
ACI 318-95, Section 7.5.4.

Tony Powers, P.E.
HDR Engineering

> ----------
> From: 	hsprague(--nospam--at)
> Sent: 	Wednesday, February 18, 1998 9:19 AM
> To: 	'seaoc(--nospam--at)'
> Subject: 	RE: Welding Rebar
> There are places in the ACI 318 seismic section that do preclude
> welding rebar together, but even if you are allowed to weld it you
> have to take a lot of precautions.
> Read the welding requirements of the AWS for rebar.  A615 rebar  is
> generally very high in carbon and must be welded with a certain amount
> of preheat depending on the mill test reports.  You have to track the
> rebar with the appropriate mill test reports and prescribe the proper
> amount of preheat or use the default preheats per AWS.  This can be a
> problem in the field.  
> A706 weldable (low carbon equivalent) rebar can be used, but it has
> not yet gained enough popularity to be readily available.  The last I
> knew very few suppliers stocked it.  You generally had to order a rail
> car load as a minimum.
> Even if you get weldable rebar, preheat or whatever; the smaller tack
> type welds generally used just to hold a mat of steel together can act
> as a stress riser and can result in a brittle failure at the weld site
> as the rebar goes ductile.
> Take the advice of a retired iron worker and tie it.  I know there are
> applications where welding a rebar assemblage is cost effective, but
> they are the exception to the rule.
> Regards,
> Harold Sprague, P.E., Office Manager
> Krawinkler, Luth & Assoc.
> 4412 W. Eisenhower Blvd.
> Loveland, CO 80537
> Voice: 970 667-2426
> Fax: 970 667-2493
> Email: hsprague(--nospam--at)