Epoxied Dowels and Plug Welds 2

[CANPRO]

I have a situation where I need to anchor something at the edge of a slab and space is at a premium...

I was thinking of placing dowels into the vertical face of the slab (about 10" thick) with epoxy, placing a plate with holes over the dowels and plug welding the plate to the dowels. I'm limited in the space I have at the slab edge to the point where I only have the room to put a 3/4" plate (no room to bolt the plate). I can extend my plate along the length of the slab to get the number of anchors to suit the loading.

This isn't so much a question, just wondering if anyone can see anything wrong with this idea, or has any success/failure experience with this.

I plan on contacting Hilti and asking about the affect the heat of welding will have on the epoxy.

Like I said, I have flexibility with the anchors so there is no specific load I'm working with yet...but it is in the range of about 5000 lbs tension/shear.

 

[connectegr]

One thought...
Plug welds are for shear only, not tension.

http://www.FerrellEngineering.com

Providing fabrication and erection efficient structural design of connections. Consulting services for structural welding and bolting.

 

[CANPRO]

I would have the end of the bar prepared at angle and welded within the hole of the plate, I don't think that would be classified as a plug weld...poor choice of words on my part.

I appreciate the quick response.

 

[connectegr]

If AWS D1 applies, what prequalified weld is to be used?

http://www.FerrellEngineering.com

Providing fabrication and erection efficient structural design of connections. Consulting services for structural welding and bolting.

 

[Ron]

Can you weld the dowels to the plate and then insert with epoxy? Weld will destroy epoxy for an inch or so into the hole.

As for the weld, bevel the dowel and use a partial penetration weld.

 

[hokie66]

Would countersunk bolts work for you? If not, I would go with Ron's approach and weld the dowels to the plate before setting in the epoxy.

 

[racookpe1978]

Is the concrete already poured around the rebar?

 

[CANPRO]

racookpe: rebar is in place and concrete is poured.

ron: I may have to use that option. The thought had crossed my mind, but I thought inserting the dowels first then cutting the holes in the plate would be easeir on the contractor incase they start hitting a lot of rebar. They may just have to drill holes then fabricate the plates accordingly.

hokie: countersunk bolts may also be an option...I hadn't thought of that. They may end up being fairly long so I'll have to check availability, but it is an option.

Thanks all for the input!

 

[Ron]

caneit...if you weld post installation, the welding will be "out of position" and more difficult to achieve. I'm not sure what your stress orientation or level is, but that could be an issue.

I like hokie66's idea of countersunk bolts....those can be obtained in any size and you have the added benefit of better adhesion to the epoxy. They will have to be pushed against the slab to maintain plate contact as you cannot tighten after installation.

An installation suggestion if you select this route:

Put duct tape over the drilled holes after proper cleaning. Puncture the tape only enough to inject the epoxy into the clean, drilled hole, completely filling the void. Put the plate in place and then drive the bolts through the tape forcing excess epoxy out of the hole. This wastes epoxy but assures epoxy all around the bolt.

 

[CANPRO]

Ron, we usually try to stay away from the contractors methods of installtion, but in this case it might be worth getting involved.

If they weld the dowels on the plate and then insert into epoxy, I don't like the fact that they won't be able to see anything after the installation. Getting a tight fit might be an issue as well with the excess epoxy spreading out between the backside of the plate and the edge of slab.

I think I might go with the countersunk bolts and pass on your installation suggestion...

Thanks again.

 

[dcarr82775]

If the dowels are welded on you can't spin the bars during installation. Maybe not a big deal depending on your loads but I have not been able to get Hilti to give me any guidance on bond reduction if the bars are not spun during installation.

 

[OHIOMatt]

One more idea, drill the holes in the concerete as required. Then provide on oversized holes in the concrete that will accept a nut. Weld the nuts to the backside of the plate. In stall epoxy. Install rods that are mostly smooth, through the nut until the thread engages. Cut and grind smooth.

 

[TXStructural]

Maybe a sketch would be in order. If you have clearance to drill and insert anchors and weld, why no clearance to bolt or do a proper anchorage?

 

[CANPRO]

I have been looking for countersunk bolts, but nothing in the length I need...I might not be looking in the right spot (or maybe I just need to let the contractor source the bolts himself). OHIOMatt, I might have to use your suggestion with the welded nuts if I can't find the bolts I need. Although I'll probably use all threaded rod rather then partially threaded.

TXStructural: This is new construction so there is plenty of room now, but nuts and bolts will get in the way of the brick/brick shelf, or so I'm told. This is one of those jobs where I have been suggesting the best route and there is always some reason why it doesn't work. This is basically my last option. Thanks for the reply.

 

[cvg]

Williams S-7, type B outer stud and insert a countersunk bolt into the end.

http://www.williamsform.com/Concret...ncrete_Anchors/reusable_concrete_anchors.html