Anchor bolt embedment close to edge

[sam3990]

Hi
In ACI the failure modes dont show any effect for anchor bolt embedment close to the concrete edge. How it ma impact the concrete breakout tensile/shear behavior. Can anyone please share any literature for the same.
Consider anchor bolt embedment 270mm and cover 40mm to the concrete edge.

Thanks & Regards
Sambhav

 

[dauwerda]

In ACI the failure modes dont show any effect for anchor bolt embedment close to the concrete edge.

This is incorrect, ACI 318 goes into great detail on the edge effects and how to account for them.

 

[jjl317]

I think the OP was talking about the edge to the bottom in their sketch (approximately concrete thickness minus embedment).

Personally, I have always just followed the ACI defined minimum concrete thickness requirements of the product in question and have never tried to justify a condition where this thickness was not achieved (though I have wondered what drove these minimum thicknesses).

 

[dauwerda]

Thanks jjl317, you are right, I totally missed the bottom edge callout in the picture.

I believe it is large ignored because it won't have an effect, or at least not one that lowers the capacity of the anchor in tension or shear. A place it does have an effect is if your anchor is also expected to resist compression (common in the utility industry), as this would be a similar failure to concrete breakout, but going down through the bottom, essentially your embedment would be the distance from the bottom head or nut of the anchor to the bottom of the concrete.

 

[icebloom]

It has an effect if your anchor is under compression, in which case the back can punch out. The tension capacity of the anchor is independent of the thickness of the member for the scenario you have shown - it only depends on embedment depth (breakout) and the bearing area at the head of your anchor (for pullout). In the calculation for shear edge breakout there is a factor dependent on the thickness of the member, which influences your capacity.

 

[SE2321]

I don't think the bottom edge distance will have any noticeable impact on the tension and shear capacities of anchors. Even under compression, it will not be a problem as compression is largely resisted by bearing stresses generated by the baseplate contact with the concrete surface.

 

[icebloom]

I don't think the bottom edge distance will have any noticeable impact on the tension and shear capacities of anchors. Even under compression, it will not be a problem as compression is largely resisted by bearing stresses generated by the baseplate contact with the concrete surface.

It depends on the context - some designs have ungrouted baseplates where the anchors are fixed to the endplate with a nut either side and there is a gap between this and the substrate. In this case the compression is transferred via the anchors themselves which can cause a punching failure through the back of the slab. If you have a grouted baseplate, then as you say the compression is transferred through the bearing and contact of the baseplate, and it would become more of a global punching failure mode that needs to be checked.