Welding to plate embedded into concrete

[DWHA]

I have ran across the situation in an industrial location where the site engineers insist on welding to embed plates. That is, steel plates embedded into concrete. The site engineers claim that the plates were cast into the concrete for the purpose of using them as weld points at later times. Has anyone ever seen this before? It has always been my understanding that the heat produced in the welding process would be detrimental to the surrounding concrete.

Please advise - Thanks!!

 

[csd72]

This is common in precast buildings though I would be careful if this connection is going to be heavily welded.

We have specified plenty of connections with continuous 1/4 inch weld with no real problems.

Use the google at the top of the page to look for previous articles on embedded plates as there have been some good threads on this.

 

[slickdeals]

I have also seen connections in precast that have a small gap between the edges of the embedded plate and the concrete which will allow the plate to expand during welding without inducing restraint stress on concrete.

 

[a2mfk]

This is done all of the time in pre-cast, tilt walls, and CIP tie beams and columns. I had never given it any thought until this post, so now I am interested in others responses. FWIW I have never had a problem with the concrete when this is done.

 

[DWHA]

Hmm, well from all of the comments so far, it is typical in precast. My situation is cast in place. Not that I can see how it would act/react any different.

 

[a2mfk]

I would think you would want to avoid welding when the concrete is "green" to prevent super-heating moisture in the concrete, possibly causing spalling and/or cracking.

 

[dharhay]

When I was a piping stress analyst in the nuclear industry, that was the common way to attach pipe supports. The concrete walls had many embedded plates that the piping support group welded square and rectangular tube steel.

I never heard of any concrete issues.

Dave Harhay
Fives Bronx

 

[Ron]

This is common in tilt-wall construction as A2 noted, which is essentially the same as cast-in-place concrete. The concrete acts as a huge heat sink and usually is not affected by the welding, as long as the welds are relatively small (1/4" fillets are common) and the plate is sufficiently thick (at least as thick as the weld size).

If you produce enough heat to hurt the concrete, you'll be rewarded with a small explosion due to expansion of vapor in the concrete voids. In order to affect the strength of concrete, you would have to maintain a high temperature (>600C) for a period of 3 to 4 hours...this doesn't occur in welding.

 

[Lion06]

We occasionally provide embed plates in walls (to support gravity beams) and routinely provide embed plates in shearwalls/grade beams/fndtn elements at braced frame columns for welding of gusset plates. we've provided them in tops of walls for wind posts, in slabs for railing posts...

Is there anything else that you can use an embed plate for besides welding to it? I suppose you could provide a shop welded connection to it and the whole unit gets cast, but they never set the embed in the right location.

 

[csd72]

What we have done a few times is to weld some threaded inserts to the rear side of the plate, that way you can get a bolted connection.

 

[bridgebuster]

Often prestressed concrete bridge girders have embedded plates that are field welded to the bearing.