Stud Rails for Beams/Joists

[Leo Baldwin]

I know ACI 318 has guidelines on stud rails for flat slabs for shear reinforcement (at columns).
We often work with one way joist slabs. Joists are 2ft o/c, 4.5" wide and 10" deep. These joists often need shear reinforcement (1st and last third of the 25ft span - roughly speaking).
#3 Stirrups are a pain to put in. O-stirrups are impossible - no room.
Could I not use stud-rails? I looked at the costs and they are not that bad.
Any insight you may have would be much appreciated.

 

[KootK]

I don't see why you couldn't do that. And it's a clever idea.

My only concern would be that the studs may have to be stacked with stud heads occurring part way up the joists. I believe that negatively affects performance so, whatever one normally does to address that in slabs, I'd think that you'd want to do the same thing here. Do fact check me on this, however, as it's been a good long time since I've contemplated stacked studs.

Other build friendly options might be single leg stirrups with 90 hooks each end with the hooks turned oriented with the longitudinal axis of the beam. Or, similarly, bent ladder reinforcing. My time the world of precast engineering has made me more comfortable with these kind of setups that I've been in the past when I always insisted that the stirrups be hooked around longitudinal reinforcing.

 

[Leo Baldwin]

Thanks for your frank insight, KootK!
I think you mean this where the stirrup develops into "itself" rather than around top or bottom main rebar?

Feedback from field is that these are super-difficult to fabricate... And some engineers do not like stirrups not being bent around primary bars....

Hence the Stud Rails - can be ordered in any height and spacing is a variable. The bottom rail comes with its own chair...

I've also looked into Dayton's Dur-O-Web custom made mesh - but they want truckload quantities...

https://www.buildsite.com/pdf/dayto...-Shear-Reinforcement-Product-Data-2162691.pdf

 

[Enginerdad]

Feedback from field is that these are super-difficult to fabricate

I can see how a continuous serpentine bar like the one shown could be hard to bend, but why not just make them individual stirrups? A single U-shape with horizontal bends at both ends. Then just lap the horizontal legs. That shape is super common and easy to make. Installation would be no harder than installing traditional transverse stirrups along the length of the beam.

 

[Leo Baldwin]

I am getting feedback that engineers often want shear stirrups to develop around primary bars... Which cannot be done with the serpentine bar...