Question about ACI 318 App. D - Avc Conc Breakout Area in Shear

[pob11646]

Avc, as defined in ACI 318 Section D.6.2, is the projected area of the failure surface on the side of the concrete member at its edge for a single anchor or a group of anchors. Now, my aim is to calculate the concrete breakout strength of anchor in shear. ca1 is the distance from the concrete edge to the axis. ha is the thickness of member in which an anchor is located, measured parallel to anchor axis, in inches.

Now, the evaluation of Acc based on ca1, ca2, s1, ha, etc. are provided for several cases. The cases are, for e.g., for when ha < 1.5ca1, or for ca2 < 1.58ca1, etc. It does not seem that these cases are all inclusive. For instance, what if my ha > 1.5ca1? Which Avc should I use then?

And why are only one or two anchors showing? What if I have 4 bolts? What if I have 2 botls, but my ha > 1.5ca1?

Hope someone can shed light on this. Thanks.

 

[Lion06]

If ha>1.5ca1, use 1.5ca1. The is because of the angle of failure (35 degrees). This is the max value it can be.

If you have 4 bolts, you have two possibilities.
First, if the anchors are welded to the plate (as in an embed plate with headed studs), you only have to consider ca1 as the distance from the edge to the row farthest from the concrete.
Second, if the anchors are not welded to the plate, then you have to consider two possibilities. The first is the same as if the anchors are welded to the plate (i.e. ca1 is from edge of concrete to farthest row of anchors), the second is with ca1 from edge of concrete to nearest row of anchor. For the second case, multiply that value by the number of rows of anchors that you have to get the total capacity (assuming that you have an equal number of anchors in each row).