Welding to embedments in concrete.

[vincentpa]

We are designing a steel walkway to attach to the side of a concrete tank wall. To attach the walkway, we are embedding plates in the concrete wall. Supports for the walkway will be welded to the embedded plates. The embedded plates are 1/2" thick. We are welding the flanges (thickness = 0.26") of a W6x15 to the plates.

The contractor raised concerns about welding the supports to the embedded plates. He is concerned the welding will create too much heat and pop out or weaken the concrete. Does anyone know of any sources that address welding embedments on concrete? Does anyone have "rules-of-thumb" or sources of information on limits for heating concrete or welding steel attached to concrete?

 

[civilperson]

The embedded plates are standard for precast connections. Maximum weld is six inches of 5/16" filet weld at one time. Wait till the temperature is ambient to add additional weld.

 

[vincentpa]

Where do I find the reference that you refer to about welding attachments to precast concrete?

 

[DarthSoilsGuy]

what does the contractor think embedment plates are for?

As far as what civilperson says, a good welder will do this anyway.

 

[mrengineer]

AISC seminar on field fixes said too much heat can cause spalling. Their recommendation is to provide thick plates (1/2" minimum for deck bearing, 3/4" for beam bearing). I have managed to stay out of trouble by using 3/4" for embed plates at beam bearing conditions.

 

[WpgKarl]

This becomes a much bigger problem when you are welding to stainless steel plates embedded in concrete. SS has a much higher coeff of expansion than regular plate steel. We have wrapped the edges of SS embed plates with 1/8" to 1/4" thick foam rod, which then allows the edges of the plate to expand into the foam.

Other suggestions - use the smallest size fillet as possible and only use as much welding as req'd for a safe design. If a 0.25" fillet works, don't bump it up to 3/8" and then the guy in the field bumps it up to one size larger becasue it feels good. This is not economical either.

Finally, the welders should be using welding procedures to minimize the build up of heat in the joints.

PS - Since you are welding the flanges to the plates - are you considering this a moment connection? Make sure you have anchors that can yield at the same level as the flanges, so the forces are put directly into the anchors if possible.

 

[UcfSE]

A typical note I have used in the past is to allow the concrete to cure at least 72 hours before welding and for the welder/GC to take precautions to avoid build-up of heat in the concrete. Pretty generic, not much information.

I would be interested in seeing a document or reference for this as well as the OP.

 

[blake989]

a decent reference for this subject can be found in the PCI Design Handbook...."decent" = they at least acknowledge the problem and provide some recommendations.

 

[rulljs]

I have a similar situation vincentpa, only I have a concrete beam 1'-6" deep and 1'-0" wide with a 6" wide by 1/2" plate is embedded along the whole span of the beam. What I want to do is weld a W8x21 or possibly W6x15 column to the embedded plate.

I don't have access to a PCI Design Handbook, does anyone have any other good referances or articles that discuss welding on plates embedded in concrete.

From the posts above (other that blake989's) i'm not sure where I can find any more information on this topic.

Any help would be appreciated.