Welding anchor bolt into an oversized hole.

[besitua]

I'm designing an embedded base plate with anchors to resist tension due to column moment. But, because the base plate must be flush with the floor, I must weld the 3/4" dia. (F1554-GR36)threaded anchor to the bottom of the 1" thick base plate.

To increase the weld capacity, can I insert the threaded rod into an oversized hole in the base plate with a plug weld? If so, how do I calculate the weld capacity?

 

[CCWG]

I don't think this would be a good application...I don't have my steel code (AISC) with me but you will find somewhere in section J plug welds should not be used in tension.

For something like this my first thought would be using a threaded weld stud. The weld machine for a 3/4" stud is quite a unit though...So another alternative could be to drill/tap the plate and install a threaded rod with loc-tite. It's an application I use in the facade industry - not sure if that would turn heads for you.

Or maybe just fillet weld around the threaded rod if that develops enough strength.

 

[BridgeSmith]

Automatically end-welded headed studs (AKA Nelson studs) could be an option for this. For bridges, we typically use them in shear applications, but I believe they can be used for tension, also. It requires proper reinforcing to provide anchorage for the studs, which I'm not well versed on, but if you'll provide more specifics about the configuration, there are several members that are (Kootk comes to mind).

Rod Smith, P.E., The artist formerly known as HotRod10

 

[JStructsteel]

Why not a weldable dowel bar developed into the footing? Plate/bars shop welded.

 

[dik]

Could you not shop weld headed anchor rods to the base plate? like a headed stud? Can you provide a 'countersunk' type of hole in the baseplate and field weld? You can use oversied washers for temporary erection, install the columns, go back and remove the anchor rod nuts and fill the countersunk hole with weld and cut and grind off? I should add... I nearly always use Gr 55S1. The price is the nearly the same and the strength is remarkably better.

Rather than think climate change and the corona virus as science, think of it as the wrath of God. Do you feel any better?

-Dik

 

[desertfox]

Hi besitua

I can't comment in the field of structural engineering but in mechanical engineering welding of commercial bolts and nuts is prohibited, this is because the heat from the welding can destroy the mechanical properties of the bolt or nut and reduce its original strength.

“Do not worry about your problems with mathematics, I assure you mine are far greater.” Albert Einstein

 

[TLHS]

desertfox, F1554 Grade 36 threaded rods are low carbon 36ksi steel, and are weldable.

 

[desertfox]

Hi TLHS

Thanks for the clarification

“Do not worry about your problems with mathematics, I assure you mine are far greater.” Albert Einstein

 

[saplanti]

You say “the base plate must be flush with the floor”. Why do you want to use this concept¿ There are certain practices for the base design, most of them require concrete base higher around 100-200 mm above the floor to prevent any kind of corrosion.
Can you please give us the reason that the base plate needs to be flash with the floor.
Thanks.

 

[dik]

That's why I always use Grade 55 S1... it's weldable and stronger.

Rather than think climate change and the corona virus as science, think of it as the wrath of God. Do you feel any better?

-Dik

 

[TLHS]

If you need the floor flat around the column, would it be easier just make a pocket in the slab, put the baseplate in there a couple of inches below top of slab, and then grout the pocket flush with the floor? The floor is flat with no anchor bolts sticking up, you don't have to screw around with the base plate, plus you've got a nice shear load path from the embeded column.