Did Hilti Make a Mistake? Or Do I Not Understand Shear Friction 4

[CDLD]

Good afternoon!

I've been looking through one of Hilti's guides (Post-Installed Reinforcing Bar Guide) and have found that they are using the bars in the compression zone as shear friction reinforcement.

It is my understanding that when a moment acts across a joint, the bars that are in tension are used as shear friction reinforcement.

I have attached a worked example from Hilti showing the bars in the compression zone being used as shear friction reinforcement, which in my opinion is wrong.

Additionally, on Hilti's Profis software package they have an explanation of their "default assumptions" for shear friction which show that they only count on bars in the compression zone for shear-transfer when moment acts across a joint.

I have a hard time believing Hilti would be wrong on this, but at the same time feel I am correct.
Am I misunderstanding shear friction or did Hilti make a mistake?

Thanks for the replies and apologies for the long post.

 

[haynewp]

Hilti has published this article where they are doing their own thing for shear friction based research. Simpson must be doing similar as I get very close results in comparison.

https://ask.hilti.com/article/shear...method-for-post-installed-rebar-design/63jbgp

 

[TLHS]

Note that you aren't double counting the tension bars. It's that the tension bars being yielded means there's already an equal amount of compression force on the concrete as part of the moment couple that can be used in friction. Basically, you have a shear friction head start when there's already moment in the beam.

Also, Hilti has different shear friction assumptions being used in different references and for different applications. I once specifically logged into Profis using a different country so that I could use a specific calculation that I wanted to look into. If I do Canadian code checks they do CSA assumptions, US ones use ACI, they definitely have an EU implementation. Then there are some specific areas where they'll go into other research. There's a semi-dowel based theory that they use for overlay reinforcing I think. The different country technical guides also go into varying amount of detail.