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RE: Welding Rebar

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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)klaalov.com


-----Original Message-----
From:	Lee, Calvin [SMTP:CAL(--nospam--at)syseng.ci.portland.or.us]
Sent:	Wednesday, February 18, 1998 11:21 PM
To:	'seaoc(--nospam--at)seaoc.org'
Subject:	Welding Rebar

Can someone direct me to a reference (code or theoretical) about why
someone should not weld rebar together?  Specifically, a mat of steel
like the type found in a spread footing or welding the spiral to the
longitudinal bars in a column, not a lap splice.

Thanks

Calvin Lee, P.E.


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