post installed anchor concrete pullout

[RJN3959]

I am looking for information on determining the concrete pullout strength for a post installed anchor. My situation is a little out of ordinary. I am very familiar with ACI 318 Appendix D however my situation is not covered. I have a steel bracket bolted to concrete. The bracket load induces a moment on the connection. The moment is transfered via tension in a post installed mechanical wedge anchor and compression between the edge of bracket and the concrete. The tension load on the anchor is about 4 times the external load due to the prying. The tensile load on the anchor and the compressive load on the concrete are typically 1 to 2" apart. The anchors are embedded 3 to 4" so the compressive load falls into the concrete breakout cone(mode that always controls the design). I know this compressive load will help with the concrete breakout but I do not believe it is as simple as taking the differnce between the anchor tensile laoding and the compressive concrete loading as the loads are not concentric. Anyone aware of any methods or references for this scenario?
thanks

 

[Lion06]

I would count on this qualitatively only as something in your back pocket to take the interaction ratio up to 1.0. I've never seen any literature that addresses how to account for this interaction.

On a different note, if the tension is being amplified by a factor of 4 due to prying, then I would look at a new arrangement. That seems way too high and could end up being even higher if small dimensional changes occur during construction.

 

[charliealphabravo]

The interaction between the bracket and the concrete depends on the stiffness of the bracket. Your problem is partly a base plate design problem since you are wanting the pressure distribution from the bracket to resist breakout. I'm not sure that this interaction is intuitive and it might be highly variable depending on variable geometry during construction.

As you probably know, post installed anchors are proprietary, especially the mechanical ones and they don't always behave like embedded or chemical anchors. It doesn't seem like understanding the failure mode you describe would be a rewarding endeavor.