Plug welds used for cast in baseplates

[rscassar]

In noticed in the latest modern steel construction that it said plug welds cannot be used to resist tension. I have regularly called up cast-in baseplates with reinforcement plug welded which are subject to moderate sized uplift forces.

If I need to weld reinforcement to a baseplate which is to be cast into concrete and subject to uplift forces, what is the best way to fix the reinforcement to the plate. I have a 1" thick plate which needs to be fixed to #8 bars. The reinforcement fixed to plate needs to transfer approximately 16kips per reinforcing bar.

All help will be appreciated.

 

[rowingengineer]

Kikflip,
you may wish to request the castin plate manual from RJB, they have tested the system. I spec drilled thru puddled weld one side and CFW the other, maybe I should review this.

An expert is a man who has made all the mistakes which can be made in a very narrow field

 

[paddingtongreen]

I don't know how you would calculate the effective area of a plug weld in tension.

Can't you weld, either fillet or penetration weld, splice lengths of rebar to the bottom of the plate and overlap them with the foundation rebar. I don't like casting baseplates in the concrete, too many voids under them.

Michael.
Timing has a lot to do with the outcome of a rain dance.

 

[hokie66]

I have seen it done in RE's way. Why wouldn't the capacity be that of two fillet welds, one on the top and one on the bottom?

 

[bones206]

We have used half-couplers welded to the bottom of the plate, then threaded rebar into the coupler.

http://www.erico.com/public/library/Concrete/LT0947.pdf

 

[TXStructural]

The usual method is to shop weld or automatic end weld deformed bars to the plate and lap as Paddington says. Optionally, mechanical splices or couplers can be used to make the plate more compact for handling.

Plug welds are usually only permitted to resist shear. If you are holding the bar slightly below the top of plate and puddling a weld on top of the bar, it is a plug weld. If you are extending the bar thru the plate and welding as with a fillet above and/or below, or tapering the hole or tip of the bar as for a CP/CJP weld, then you would probably consider those welds differently.

I think it is the puddled weld metal in a plug that causes a problem. In addition to shrinkage issues, there is no way to see the weld-base metal interface to evaluate fusion, and no way to inspect important features of the weld. Also consider that a true plug weld involves two relatively thin pieces of metal that are only bonded by a thin line of weldment along a circumference.

 

[paddingtongreen]

You know, I'm not sure we are all on the same wavelength here.

My understanding, and I can see that TXStructural has the same understanding, is of two plates with a hole in only one of them, and the hole filled with weld metal to connect the two together.

The full or partial penetration weld used to splice a bar end to a plate is not a called a plug weld.

Look here:

http://www.unified-eng.com/scitech/weld/plugslot.html

Michael.
Timing has a lot to do with the outcome of a rain dance.

 

[rowingengineer]

I think we are all talking about the same type of weld just a different application.

An expert is a man who has made all the mistakes which can be made in a very narrow field

 

[paddingtongreen]

rowingengineer, are we talking of punching a hole for a rebar halfway though it? In that case, I think a fillet weld would work, but I don't know how to realistically value the middle of the plug if the bar is in tension. I guess that is what hokie meant. It does seem to be a waste of effort though.

Michael.
Timing has a lot to do with the outcome of a rain dance.

 

[Gumpmaster]

The PCI Design Manual (Figure 6.15.4 & 6.15.5 in the 5th ed) shows a couple of options. It's a fast, easy table that shows the minimum weld size and plate thickness to fully develop a bar.

 

[rscassar]

Thanks everyone for their contribution, I have posted a picture of what I am trying to achieve.