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# ACI Shear Lug with Tension

## ACI Shear Lug with Tension

(OP)
When designing a the anchor rods that go into a pier for tension and shear, the interaction equation in appendix D is Nua/Phi*Nn + Vua/Phi*Vn < 1.2. I believe the strength is the governing limit state for both shear and tension. But if you design a shear lug to handle the shear, is this interaction equation still appropriate?

In a design example i received from the ACI anchorage to concrete seminar, they used anchor reinforcement to resist tension and a shear lug to resist shear. However, no interaction equation was used in that design. When using the Hilti Profis anchor, even if i indicate that there is anchor reinforcement for both shear and tension, they use the interaction equation. They use the 'utilization ratio' combining the max shear and max tension ratios (whether they are steel strength, concrete strength, pryout, etc).

Is the interaction equation applicable when using anchor rods for tension and a shear lug for shear?

Does anyone have any insight as to why you combine steel strength with concrete strength in the interaction equation?

### RE: ACI Shear Lug with Tension

You can also use the interaction expression from RD.7 that raises the terms to the 5/3 power and limits it to 1.0. There is a graph in the commentary that compares the two.

You don't have to worry about interaction if you can ensure all the tension goes into anchor rod and all the shear goes into the shear lug... but I don't think you can realistically ensure this. Maybe, but I would like to see the setup if you consider ignoring interaction.

Also, Profis is a design tool for engineers to use in very cookie-cutter situations. For something more complicated, I would calculate anchorage to concrete by hand.

You don't interact steel utilizations with concrete utilizations, they must be considered separately. Concrete utilizations get interacted together using the tri-linear approach or the 5/3 approach from the commentary. For steel utilizations I interact these raised to the power of 2 and limited to 1 when summed. I get this approach and power from the AISC. I have submitted designs with this approach in at least NC and FL with success.

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