Clearance requirement for welded shear stud installation 1

[Enginerdad]

I'm in the process of designing a UHPC beam end repair which requires welding shear studs to the existing beam web and then encasing the beam end in UHPC to create a new load path for the compression in the deteriorated web. If you're unfamiliar, here's a cool little video explaining the process.

In my situation, the existing beam has a double bearing stiffener which are 6" on-center and 1/2" thick each (see image below). What I want to do is put a column of 3/4" shear studs in between the stiffeners as shown by the red circles, but I don't know how to be sure the 5-1/2" clear space between bearing stiffeners is enough for the installation of studs. Does anybody have a reference on minimum installation clearance for studs?

 

[JoshPlumSE]

That's a pretty cool type of repair in that video.

What I want to do is put a column of 3/4" shear studs in between the stiffeners as shown by the red circles, but I don't know how to be sure the 5-1/2" clear space between bearing stiffeners is enough for the installation of studs. Does anybody have a reference on minimum installation clearance for studs?

To me, this seems like the stud installation for a composite beam.... just turned on it's side. Maybe not exactly the same, but similar. For this type of construction, we typically use 3/4" studs as well. AISC chapter I8 has requirements that may help:
I8.2d(b): "Steel anchors shall have at least 1" of lateral concrete cover in the direction perpendicular to the shear force.
I8.2d(c): "Min distance from ctr of a steel anchor to a free edge in the direcction of the shear force shall be 8" (for normal wgt concrete) or 10" (for lightweight)."
I8.2d(d): Min center to center distance for headed studs shall be 4 diameters in any direction. If the anchors are not within steel decking, then 6 diameters.

I don't think clearance would be much of an issue. As these studs are frequently installed in composite beam decking that is only 6 inches wide at the base of the flute. And, for beam flanges that are only 6 inches wide.

That being said, I'm certain there have to be research papers or thesis written by the folks who put together that video. They should have some guidance about what the testing supports in terms of stud placement and clearance.

 

[JoshPlumSE]

Honestly, I would contact that researcher directly to see if she had any issues with how you are planning on implementing her published technique.

Personally, it looks like the biggest challenges are going to be related to how to form and pour the concrete. The stud installation sounds like the simplest part of it.

 

[Enginerdad]

Personally, it looks like the biggest challenges are going to be related to how to form and pour the concrete. The stud installation sounds like the simplest part of it.

You're definitely right about that. The forms have to be water-tight due to how thin and flowable UHPC is. Typically the contractor has to build a mock-up of his form plan to make sure it's tight ahead of time. At $3,000 per yard (installed) you don't want to be leaking any material.